A selection of specialist mastic joint sealant products for trade professionals & home users

MASTIC JOINT SEALANTS

Almost 50 years of mastic joint sealants experience

Our speciality for almost 5 decades, mastic joint sealants make the core of our entire product range, from trade standard, economical kitchen & bathroom sealants in white & clear, to premium, long-lasting sanitary silicones in literally 100’s of colour options, to technologically advanced natural stone sealants, high-spec. facade mastic sealants and structural silicones. We’re fully onboard with the latest colour match requirements thus, we keep a large selection of RAL coloured sealants as well as providing a specialist, exact sealant match service with minimal fuss. We stock all types of sealing compounds, in all the latest materials available on the market today, manufactured by the biggest and most trusted global sealing, bonding & waterproofing names such as 3C Sealants, Adshead Ratcliffe (ARBO), C-Tec Ltd. (CT1), DL Chemicals, Dow Corning (DOWSIL), Everbuild, Fosroc, Geocel, illbruck, Mapei, Nullifire, OTTO-Chemie, Shell, Sika & Tremco. Yes other companies certainly sell sealants online and even undercut us sometimes, but we have ‘literally’ the largest mastic sealant supplies in London, Essex, Middlesex or Herts.

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What's The Difference?

Mastic Joint Sealant Materials Explained...

Mastic Or Sealant
What’s the difference between a mastic & a sealant ?

The simple answer is nothing! They are one and the same thing!

Mastic is generally an old-fashioned name that was used as an umbrella term covering the early materials such as polysulphide (polysulfide) polyurethane, oil-based and butyl, that were used to ‘seal’ and/or waterproof gaps & joints and it’s a name that’s stuck around and is still widely used to this day to identify the many types of products in cartridges, foil sausages and tins available on the market. The term ‘mastic’ is used and understood by pretty much all tradespeople and public alike and doesn’t seem to be disappearing anytime soon so we still refer to pretty much all our sealant products as mastic. It could be said, that MASTICS are SEALANTS but SEALANTS are not actually MASTICS (if that makes sense) Either way, for the purpose of covering all bases, you’ll frequently see the descriptions written as ‘Mastic Joint Sealants’ throughout this website and our e-shop Sealants Online.

The words themselves are explained in a little bit of detail on the website: https://wikidiff.com/sealant/mastic

Here’s a snippet of it:

SEALANT – Any material used to seal a surface so as to prevent passage of a fluid.

MASTIC – A flexible, waterproof cement used as an adhesive, sealant or filler.
Acetoxy Sealants
Used exclusively internally and widely recognised by it’s strong, vinegar odour, acetoxy sealants are silicone-based and contain acetic acids that are released during the curing process. Acetoxy sealants are nearly always, (but not restricted to) use in areas where high humidity is expected, such as kitchens, bathrooms and the inside of frames. The colour ranges are As the acetic acid is aggressive to porosity, acetoxy sealants are not recommended for porous substrates such as natural stone worktops and sanitary ware etc. where a neutral cure, non-staining sealant should be used instead.

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Acrylic Sealants
Used internally and widely known as caulking or caulk (often incorrectly spelt as cork or chalk), acrylic sealants are water-based products that offer a cost-effective alternative to silicone in many simple gap-filling applications, having varying degrees of flexibility (depending on the quality of the product) and offering a useful characteristic of over-paintability which is all but impossible with silicone! We stock standard decorators caulk / painters caulk (often known by the generic name painters mate) fillers and intumescent acrylic sealants that are fire grade certified.

The main drawback of an acrylic sealant is elasticity. Acrylics are fairly rigid when dry, and are intended for use in areas with minimal expansion and contraction.

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Bitumen Sealants
Also known as asphalt, bitumen sealants have natural adhesive properties and are used mainly to go up against or seal other bitumen-based materials such runways, road & roadsides, roofing felts etc. and any other application where a compatible bitumen sealant is required. The materials itself is described on Wikipedia as follows: Asphalt, also known as bitumen (UK: /ˈbɪtjʊmɪn/, US: /bɪˈtjuːmən, baɪ-/),^[1] is a sticky, black, and highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term asphaltum was also used.^[2] The word is derived from the Ancient Greek ἄσφαλτος ásphaltos.

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Butyl Sealants
A rare product nowadays, butyl sealants are used mainly to seal against specialist rubber materials such as neoprene or EPDM. As they’re are solvent-based, rubberised products, butyl rubber sealants offer low to moderate movement capabilities and have a life expectancy of only 2 to 10 years but are a often a good choice for waterproofing overlapping joints, such as gutters and below-grade applications, such as foundations and offer an excellent weatherproof seal.

The drawback of butyl mastic joint sealants compared to other materials is that these products are very stringy & gooey, meaning that they’re difficult to apply and tool off to a neat finish, and are notoriously slow curing. Butyl sealants are at their most efficient when they’re applied to open substrates between similar surfaces.

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Epoxy Sealants
Often used and thought of as a sealer or coating, epoxy sealant can be also be found in tins as 2-part joint sealants for various specialist applications such as bedding glass balustrades into channels, securing bars etc. into different substrates and other situations where a structural or engineered, hard and solid material is required. We stock a small selection of epoxy mastic joint sealants available to collect or deliver.

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High Modulus Silicone Sealants
Usually associated with internal sealing of such applications as sanitary ware in bathrooms, shower rooms & wet rooms etc. as well as, countertops, sinks & units etc. in kitchens and other areas subject to high humidity, high modulus silicone products are less able to accommodate movement compared to low modulus sealants, but will make a stiffer and more rigid final seal. The high modulus sealant products tend to withstand repeated cleaning more efficiently than the softer, more flexible, low modulus products thus are often used around tiles and on connecting joints from wall to floor which are constantly mopped and scrubbed etc. High modulus silicone sealant (or HM silicone sealant as it’s widely known) have fungicides added to them to give them far greater anti-mould properties and usually contain a chemical cure system such as acetoxy which gives the product the trademark strong odour, often likened to vinegar.

SOME FACTS…

There’s a very common misconception of EXACTLY makes a silicone sealant (or any other mastic sealant) HIGH MODULUS (or HM) and, over the years, its become widely accepted in all trades that when a product is named HM it automatically means that the product is HIGH MODULUS but below is an explanation from Wikipedia of where the word ‘Modulus’ comes from and what it means scientifically:

An elastic modulus (also known as modulus of elasticity) is a quantity that measures an object or substance’s resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is defined as the slope of its stress–strain curve in the elastic deformation region:^[1] A stiffer material will have a higher elastic modulus. An elastic modulus has the form: λ def= stress (over) strain.

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Modified Polymer/Silane (MP / MS) Sealants
Modified polymer or hybrid polymer sealants (also known as modified silane or MP Sealants or MS Sealants) although mainly thought of (and used) as adhesives, these products are also quite often used as sealants having gained popularity in recent years as a modern, more efficient alternative to old-fashioned polysulphide (polysulfide) and polyurethane sealants, combining the most useful characteristics of these mastic joint sealant materials with the added desirable qualities of being applicable in wet conditions, being widely overpaintable and generally have excellent adhesion to almost ALL substrate surfaces without the addition of a pre-treatment primer.

Wikipedia says: Silyl modified polymers (SMP, also silane-modified polymers, modified-silane polymers, silane terminated polymers, etc.) are polymers (large, chained molecules) terminating with a silyl group. SMPs are the main components in solvent-free and isocyanate-free sealant and adhesive products.^[1] Typically the sealant products manufactured with silyl modified polymers have good adhesion on a wide range of substrate materials, and have good temperature and UV resistance.

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Low Modulus Silicone Sealants
Versatile and hard-wearing, Low Modulus silicone sealants accommodate more movement and thus require a HIGHER movement accommodation than high modulus silicone sealants, low modulus silicone sealants are most often used for exterior joint sealing work, doing a fantastic job of weather sealing connection joints and expansion joints in buildings. Typical examples of low mod. sealant applications are; sealing between ‘structure’ substrates such as external brickwork and windows or door frames etc. that expand greatly. There’s lots of generic ‘cheap’ low mod sealants on the market which claim to do a good job of this type of work, but be warned, these are usually always bulked out with solvents and other ‘filler’ materials and will fail when movement occurs as they will shrink considerably. We stock a large selection of the highest quality low modulus silicone sealants available in literally hundreds of colours.

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Polysulphide (Polysulfide) Sealants
Produced for decades by many manufacturers for the construction industry as a whole, polysuphides (also known as polysulfides) have now, all but been discontinued and replaced by modern technology materials such as Polyurethane, Modified Polymer/Silane and Hybrid Polymer. The main and most important reason for this shift is health & safety considerations, being that polysulphide sealants were formulated with substances now identified as toxic or a ‘hazard’. With this in mind and the constantly improved performance and costs of the alternative materials, polysulphides are fading out of fashion. However, there are some old stool enthusiasts who wish to use these products and thus a small number are indeed still available to order.

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Polyurethane Sealants
Although not quite as UV stable as silicone, polyurethane sealants have been a solid choice for many tradesmen for decades due to them exhibiting superb watertightness when fully cured, remaining permanently elastic in all weather conditions and temperatures. Often used primarily as adhesives, polyurethane sealants have good adhesion to fibre glass thus are also ideal for sealing applications in industrial & commercial vehicle assembly, including trains, cars, lorries, trucks, caravans, mobile homes, motor homes and motor cycles.

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Silicone Sealants
Long considered the ‘go to’ for sealing & bonding, silicone sealants are the best known mastic joint sealants and offer the most UV stable seal on a multitude of substrates, the best movement accommodation and are easily the most versatile sealant product in terms of application, coping well with both internal and external waterproofing solutions. Silicone mastic joint sealants are well-known to be the easiest and most user-friendly to ‘tool off’ to a neat and tidy finish, which is very high on the list of criteria for mastic sealant application as a whole. As broken down above, the most common types of silicone sealant are high modulus silicone (HM) & low modulus silicone (LM) but there’s also a ‘middle’ ground with Mid Modulus or Neutral cure silicone sealants, most commonly used for applications in natural stone or laminated glazing etc. where non-staining or non-leeching is required (often characteristics of the oils used in standard low modulus or high modulus silicones)

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The best way to determine product choice is by deciding on what it's used for

Mastic Joint Sealants By Type Or Application

Internal (inside)

Anti-Mould Sealing
For areas where high humidity causes mould growth issues, mastic sealants with anti-mould fungicides added is crucial. Swimming pool, changing room, wetroom, bathroom and kitchen areas often carry a familiar, yet uninvited visitor, mould, which isn’t just an eyesore, it’s also a detriment to health and can be a serious issue! Concentrated mainly, but not exclusively on acetoxy silicones, the anti mould mastic sealant market is constantly researched and tested with new products emerging as the technology evolves.

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Acoustic Sealing & Gap-filling
When sound integrity is required through door frames, dividing walls etc. most often, the weak links are the areas where there’s small gaps, cracks or open joints, so it’s critical to use a specific sealant with high acoustic properties. These dedicated mastic sealants are usually acrylic or water based caulks and more often than not are also categorised and certified as intumescent sealants, they only come in white or grey colour.

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Anti-Pick / Non-Pick / Secure Sealing & Gap-Filling
In environments where a seal or bed needs to have a harder, final cure than standard mastic joint sealants, to deter humans or animals from physically ‘digging’ or ‘picking’ the product out from the joint, but with a slight degree of flexibility for movement, such as police holding areas, prison cells, pedestrian walkways or other areas vulnerable to vandalism, a specialised anti-pick mastic sealant or secure grade mastic sealant is required.

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Aquarium & Glass Block Sealing
To seal or repair aquariums, from humble, home fish tanks to large, commercial viewing enclosures, decorative glass block walls to sculptured glass block installations, sealing should be a careful consideration and requires specialist, tried, tested and certified aquarium mastic joint sealants, manufactured from silicone.

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Balustrade & channel bedding & sealing
With good adhesion to glass, concrete, stone, metals and many other common building substrates, specialist balustrade sealants are extremely tough but cure fully to allow a small degree of movement accommodation, essential for bedding in and also optionally capping or sealing balustrades.

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Bathroom / Shower / Sanitary sealing
Sealing connection joints around sanitary ware such as baths, showers, sinks, vanity units and toilets and the internal frames in bathrooms has long been the job of high modulus silicone sealants due to their excellent mould resistance and good, solid final cure. These bread & butter products for specialist mastic sealant applicators, plumbers, builders and diy enthusiasts have evolved over the years to satisfy the evolution of interior design, with literally 100’s of coloured bathroom silicone sealants readily available. Concentrated mainly, but not exclusively on acetoxy silicones, the bathroom mastic sealant market is constantly researched and tested with new products emerging as the technology evolves.

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Boat & Ship Sealing
For coping with all marine repair & seal applications, both fresh water and sea water environments require specialist mastic sealants. Building, maintenance and refurbishment jobs on boats and ships, range from sealing and repairing decking, (which requires what is widely known as ‘deck caulking’ or ‘decking mastic’) to sealing and waterproofing port holes and around fittings etc on deck, below deck and undersides. The materials used for boat and ship mastic sealants are usually silicone or polyurethane.

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Caravan sealing
Just a few years ago, it came too the attention of the major manufacturers, that a host of ‘make-do’ mastic sealant products were generally used to seal inside caravans.
Now, you can buy dedicated, tested and trusted, professional, high quality caravan mastic joint sealants manufactured by Sika and Geocel (part of the Dow group) and get the job done right the first time!
These adhere perfectly to a variety of substrates inside the caravan and are suitable for a wide range of sealing applications.

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Clear / transparent sealing
Often with internal joint sealing, an invisible or inconspicuous joint is preferred as opposed to coloured sealant. As advised on our e-shop for clarity (excuse the pun) the term ‘Clear’ in the mastic sealant industry is sometimes confusing as many customers are looking for different kinds of ‘Clear’. To be sure you choose the correct product, please see the following information regarding the names used to describe the colours:

CLEAR SEALANT – uncloudy, glass-like in appearance (not totally see-through,varies in shade from sealant to sealant, occasional tendancy to yellowing due to UV over time, especially in external, low modulus sealants)
CRYSTAL CLEAR SEALANT – completely transparent and unclouded. (usually a bit more expensive material to produce, but particularly suited to glass to glass joints etc.)
TRANPARENT SEALANT – allowing light to pass through so that objects behind can be distinctly seen. (a good ‘happy medium’ for most internal and external joints where a colour cannot be matched or just suits the decoration etc.)
TRANSLUCENT SEALANT – allowing light, but not detailed shapes, to pass through; semi-transparent. (cloudy but often neatly disappears into joints, suited to joints where glass meets glass or other substrates)

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Cold room / clean room sealing
For specialist applications such as cold room food storage or clean room areas (Clean rooms are described by wikipedia as follows: A cleanroom or clean room is a facility ordinarily utilized as a part of specialized industrial production or scientific research, including the manufacture of pharmaceutical items and microprocessors.) the use of a cold room sealant or clean room sealant is required. These sealants are thoroughly tested and subsequently certified specifically for these tasks.

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Coloured Joint Sealing
With the evolution of interior design and the advancements in manufacturing, the requirements for mastic sealants in colours has grown exponentially in recent years. The clinical, standard white and grey silicones of the past still have mass appeal for their simplicity and ability to ‘finish’ a joint but there’s now literally 100’s of shades & tones of white & grey silicone sealants to choose from, plus the multitude of other colours available amongst the internal ranges of silicones. There’s also a huge market for coloured silicone sealants made specifically to match the universal RAL colour system. A large percentage of these RAL numbers are stock items for us.

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Construction Sealing
If you’re looking for high quality mastic joint sealants but want to cut out the technical fluff, there’s several products that serve as all-rounders and cater for most general, internal tasks in the professional construction trade and the DIY construction market. Use construction sealants as your daily, reliable sealing and waterproofing go to’s or just as and when you need them for your snagging lists.

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Sealing Damp / Wet Joints
Often, when time is a consideration, the surfaces or joints that require a seal internally are constantly or already damp (even wet) and drying the area isn’t an option (such as in basements, non-ventilated bathrooms etc.) There does exist a selection of damp tolerant sealants and wet tolerant sealants for application directly. Waterproof in nature when fully cured, the materials used for this sort of application are hybrid polymers, polyurethane, bituminous or epoxy based and come in both 1-part cartridge form and 2-part tin or pack form.

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Expansion Joint Sealing
For internal expansion joints subject to high or standard, natural movement over time, low modulus mastic sealants such as polyurethane, polysulphide or the newer technology modified polymer or hybrid polymer is often used, but by far the most popular material used is neutral-curing, low modulus silicone sealant. Expansion joints could be in concrete, brickwork, timber and other substrates.

Please note; As well as vertical and horizontal wall and roof joints, expansion joints are also widely used for internal flooring, such as saw cuts and perimeter joints requiring a more rigid and hard-wearing cured sealant, these can be found in our FLOOR SEALANTS section – click here to see

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Fire Stopping & Intumescent Sealing
Specialist fire protection mastic sealants for internal use are fully certified by the appropriate governing bodies and approved for professional use. The main difference between the 2 types of fires sealants is as follows:
- Intumescent sealants are made from acrylic and swell to fill gaps & voids to stop the passage of fire. A description of the word is on Wikipedia – click here to see.
- Firestop sealants are made from silicone and are designed to work as flame & smoke retardants, to seal cable openings and joints in walls & floors to stop the penetration of fire. A description of the word is on Wikipedia – click here to see.
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Floor Joint Sealing
Joints in floors range from simple, decorative finishes to full-on industrial seals such as aircraft runways, petrol stations and roads. Whilst there’s floor sealant products that take care of a multitude of applications, there’s also dedicated mastic sealant products that excel in specific situations. Different materials such as neutral cure silicone, polysulphide, polyurethane, epoxy resin and hybrid polymer have varying degrees of shore A hardness, (the fully cured, final solidity of the seal) and thus each application of various floor joints need to be assessed for the type of traffic they will endure, examples of this would be; saw cuts in warehouses with forklifts passing over them, vehicular trafficked floor joints in carparks or areas where lots of people pass over regularly. In each case, the hardness versus some degree of movement needs to be weighed up.

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Food Safe Joint Sealing
Industry-standard, ‘food safe’ mastic joint sealants manufactured by trusted and popular names in the sealant industry, are fully certified and suitable for use in and around areas where food is processed and/or served, providing protection from bacteria, MRSA, E. Coli and Salmonella. Containing specialist food-grade fungicides, these food-safe mastic joint sealant products are ideal for sealing joints in commerical and industrial kitchens, processing factories, canteens and food storage facilities.

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Internal Glazing & Glass To Glass Sealing
A stable choice in the house-building, construction industry for many years, glass construction and pre-assembled glazing has also hugely increased in popularity in commercial and industrial building envelopes. Glazing mastic joint sealants are usually neutral cure silicone sealants, especially when the glass joints to sealed are laminated glass which will almost always react badly to solvents etc.

As well as the actual glass being capped, sealed or bonded, there’s also very important differences in specification and certification between structural glazing sealants and weather seal glazing sealants and each application should be looked at individually when considering the correct glazing sealants to use, consulting the necessary technical representatives from the relevant manufacturers where appropriate.

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High Temperature Sealing
Applications where a high service temperature is present or a substrate reaches unusually high temperatures (such as chimneys, gas flues, tile stoves and auto parts etc.) A specialist high temperature sealant is required.

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Kitchen Sealing
Applications where a high service temperature is present or a substrate reaches unusually high temperatures (such as chimneys, gas flues, tile stoves and auto parts etc.) A specialist high temperature sealant is required.

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Internal Marine Sealing
When resistance to sea water is required, specialist, certified marine mastic sealants are necessary. Made from either silicone, polyurethane or newer polymer materials these products are ideal for sealing joints in decking, seating, walls & floors on boats, ships and other marine applications, but marine sealants will also cope well with simple crack repairs and glass remedial works such as sealing around port holes, fixtures & fittings, making the vessel watertight, safe and secure.

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Natural Stone Sealing
Sealing joints in natural stone internally such as marble, granite, limestone, sandstone and other porous & non-porous natural stone can be problematic due to the reaction with the cure systems in many mastic sealants. The spread of oils, causing migratory staining or ‘leeching’ as its sometimes known, into and onto the stone surface and edges not only looks very unsightly but also cases harm to the stone itself! This issue is often over-looked by DIY people when they seal their own natural stone joints, but it’s also more common than you’d expect from trade professionals too, due too lack of knowledge or sometimes lack of care 🙁 We have a huge range of only the highest quality natural stone mastic sealants that guarantee not to bleed into the natural stone or cause unslightly migratory staining that standard silicone sealants usually cause!

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Non-Staining Silicone Sealants
Sealing joints in natural stone internally such as marble, granite, limestone, sandstone and other porous & non-porous natural stone can be problematic due to the reaction with the cure systems in many mastic sealants causing staining. The spread of oils, causing migratory staining or ‘leeching’ as its sometimes known, into and onto the stone surface and edges not only looks very unsightly but also cases harm to the stone itself! This issue is often over-looked by DIY people when they seal their own natural stone joints, but it’s also more common than you’d expect from trade professionals too, due too lack of knowledge or sometimes lack of care 🙁 We have a huge range of only the highest quality non-staining mastic sealants that guarantee not to bleed into the natural stone or cause unslightly migratory staining that standard silicone sealants usually cause!

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Paintable (over paintable) Sealing
We’re often asked if any internal mastic sealants are over paintable and the simple answer is usually no, but there does exist some products that are formulated slightly different than most and then thoroughly tested for paintability and do a good job of it! What most people class as ‘mastic sealants’ are usually silicone products and silicones are notoriusly bad for taking a coating of any kind, so most paints will simply bead straight off and not stick at all and if they do, will almost certainly crack and peel with even the slightest movement. There is one single silicone product that somehow manages overpaintablity which is called OTTOSEAL S113

The other option for internal over paintable sealants (as mentioned earlier) is to use non-silicone products such as acrylic, hybrid polymer, modified polymer or modified silane that cure and dry differently and thus will take coatings far better. As there’s multitudes of different paints, varnishes and coatings with entirely different ingredients, in each case, a small test area is haughty advised.

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Plumbing Sealing
Specialist mastic sealants formulated for various plumbing applications such as pipework, ducting and around sanitary fittings etc. These plumbing mastic sealant products are best suited to plumbers, boiler engineers, heating technicians and indeed any other professional tradesmen or DIY enthusiasts who need a watertight seal whilst plumbing.

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RAL Coloured Sealing
RAL colours have long been the ‘goto’ in the manufacturing industry for colour-coding for internals and thus a natural progression for matching mastic sealants to the substrates, wether it be frames, floors, walls or fittings & fixtures. As well as stocking a large selection of mastic sealants made especially to exact RAL colours, we also have a specialised colour-matching service (to ANY RAL colour or indeed any other colour from a physical sample)

Here’s what wikipedia has to say about RAL colours: RAL is a colour matching system used in Europe that is created and administrated by the German RAL gGmbH^[1] (RAL non-profit LLC), which is a subsidiary of the German RAL Institute. In colloquial speech RAL refers to the RAL Classic system, mainly used for varnish and powder coating but nowadays there are reference panels for plastics as well. More information can be found here

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Refridgeration Sealing
For sealing in areas subject to refrigeration such as refrigeration units in hospitals and clean rooms, commercial premises where intermittent food contact is likely and any other areas inside or around refrigeration, specialist refrigeration mastic sealants are required. These products contain a food grade fungicide to resist mould growth and protects against bacteria growth, MRSA, E.Coli, and Salmonella.

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Self-Levelling Sealing
Used for all horizontal joints (especially floor joints) including perimeters, saw cut channels, concrete slab expansion joints and more, self levelling mastic sealants are an especially useful and time-saving method of waterproofing and dustproofing. Simply gunned out to an appropriate depth and left to find work it’s magic and find it’s way to the depth, width and length of the enclosed joint, these products are becoming ever popular with all sorts of trades people for their ease of use and fantastic finish.

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Structural / Hurricane / Impact Sealing
When an internal joint seal or bond is required for either structural bonding or structural sealing (usually for glazing) We also keep high impact, hurricane tested & bomb-blast grade, structural sealants, approved for use with specialist safety glass & safety window film systems from Pilkingtons and 3M etc. Often these structural mastic sealants are specified for useably by architects as per the manufacturers specification and whilst the products are used in the production of specialist glazing at factory level, structural sealants are often used directly by trade professionals for structural installation and structural remedial works.

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External (outside)

Anti-Pick / Non-Pick / Secure Sealing & Gap-Filling
In environments where a seal or bed needs to have a harder, final cure than standard mastic joint sealants, to deter humans or animals from physically ‘digging’ or ‘picking’ the product out from the joint, but with a slight degree of flexibility for movement, such as police holding areas, prison cells, pedestrian walkways or other areas vulnerable to vandalism, a specialised anti-pick mastic sealant or secure grade mastic sealant is required.

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Balustrade & channel bedding & sealing
With good adhesion to glass, concrete, stone, metals and many other common building substrates, specialist balustrade sealants are extremely tough but cure fully to allow a small degree of movement accommodation, essential for bedding in and also optionally capping or sealing balustrades.

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Boat & Ship Sealing
For coping with all marine repair & seal applications, both fresh water and sea water environments require specialist mastic sealants. Building, maintenance and refurbishment jobs on boats and ships, range from sealing and repairing decking, (which requires what is widely known as ‘deck caulking’ or ‘decking mastic’) to sealing and waterproofing port holes and around fittings etc on deck, below deck and undersides. The materials used for boat and ship mastic sealants are usually silicone or polyurethane.

BUY BOAT & SHIP SEALANTS ONLINE
Caravan sealing
Just a few years ago, it came too the attention of the major manufacturers, that a host of ‘make-do’ mastic sealant products were generally used to seal inside caravans.
Now, you can buy dedicated, tested and trusted, professional, high quality caravan mastic joint sealants manufactured by Sika and Geocel (part of the Dow group) and get the job done right the first time!
These adhere perfectly to a variety of substrates inside the caravan and are suitable for a wide range of sealing applications.

BUY CARAVAN SEALANTS ONLINE
Clear / transparent sealing
Often with internal joint sealing, an invisible or inconspicuous joint is preferred as opposed to coloured sealant. As advised on our e-shop for clarity (excuse the pun) the term ‘Clear’ in the mastic sealant industry is sometimes confusing as many customers are looking for different kinds of ‘Clear’. To be sure you choose the correct product, please see the following information regarding the names used to describe the colours:

CLEAR SEALANT – uncloudy, glass-like in appearance (not totally see-through,varies in shade from sealant to sealant, occasional tendancy to yellowing due to UV over time, especially in external, low modulus sealants)
CRYSTAL CLEAR SEALANT – completely transparent and unclouded. (usually a bit more expensive material to produce, but particularly suited to glass to glass joints etc.)
TRANPARENT SEALANT – allowing light to pass through so that objects behind can be distinctly seen. (a good ‘happy medium’ for most internal and external joints where a colour cannot be matched or just suits the decoration etc.)
TRANSLUCENT SEALANT – allowing light, but not detailed shapes, to pass through; semi-transparent. (cloudy but often neatly disappears into joints, suited to joints where glass meets glass or other substrates)

BUY CLEAR SEALANTS ONLINE
Construction sealing
If you’re looking for high quality mastic joint sealants for external use but want to cut out the technical fluff, there’s several products that serve as all-rounders and cater for most general, external tasks in the professional construction trade and the DIY construction market. Use construction sealants as your daily, reliable sealing and waterproofing go to’s or just as and when you need them for your snagging lists.

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Sealing Damp / Wet Joints
Often, when time is a consideration, the surfaces or joints that require a seal externally are constantly or already damp (even wet) and drying the area isn’t an option (such as on timber buildings, areas where sunlight cannot reach etc.) There does exist a selection of damp tolerant sealants and wet tolerant sealants for application directly. Waterproof in nature when fully cured, the materials used for this sort of application are hybrid polymers, polyurethane, bituminous or epoxy based and come in both 1-part cartridge form and 2-part tin or pack form.

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Expansion Joint Sealing
For external expansion joints subject to high or standard, natural movement over time, low modulus mastic sealants such as polyurethane, polysulphide or the newer technology modified polymer or hybrid polymer is often used, but by far the most popular material used is neutral-curing, low modulus silicone sealant. Expansion joints could be in concrete, brickwork, timber and other substrates.

Please note; As well as vertical and horizontal wall and roof joints, expansion joints are also widely used for external flooring, such as saw cuts and perimeter joints requiring a more rigid and hard-wearing cured sealant, these can be found in our FLOOR SEALANTS section – click here to see

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Facade Sealing
Façades are often the first thing people see as the principal front of a building that faces onto a street or open space. Sealing between cladding, connecting joints or fixtures requires a high quality, weathertight sealant with good UV resistance.

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Fire Stopping & Intumescent Sealing
Specialist fire protection mastic sealants for external use are fully certified by the appropriate governing bodies and approved for professional use. The main difference between the 2 types of fires sealants is as follows:
- Intumescent sealants are made from acrylic and swell to fill gaps & voids to stop the passage of fire. A description of the word is on Wikipedia – click here to see.
- Firestop sealants are made from silicone and are designed to work as flame & smoke retardants, to seal cable openings and joints in walls & floors to stop the penetration of fire. A description of the word is on Wikipedia – click here to see.
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Floor Joint Sealing
Joints in external floors range from simple, decorative finishes to full-on industrial seals such as aircraft runways, petrol stations and roads. Whilst there’s floor sealant products that take care of a multitude of applications, there’s also dedicated mastic sealant products that excel in specific situations. Different materials such as neutral cure silicone, polysulphide, polyurethane, epoxy resin and hybrid polymer have varying degrees of shore A hardness, (the fully cured, final solidity of the seal) and thus each application of various floor joints need to be assessed for the type of traffic they will endure, examples of this would be; saw cuts in warehouses with forklifts passing over them, vehicular trafficked floor joints in carparks or areas where lots of people pass over regularly. In each case, the hardness versus some degree of movement needs to be weighed up.

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External Glazing & Glass To Glass Sealing
A stable choice in the house-building, construction industry for many years, glass construction and pre-assembled glazing has also hugely increased in popularity in commercial and industrial building envelopes. Glazing mastic joint sealants are usually neutral cure silicone sealants, especially when the glass joints to sealed are laminated glass which will almost always react badly to solvents etc.

As well as the actual glass being capped, sealed or bonded, there’s also very important differences in specification and certification between structural glazing sealants and weather seal glazing sealants and each application should be looked at individually when considering the correct glazing sealants to use, consulting the necessary technical representatives from the relevant manufacturers where appropriate.

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Lead Sealing
Specifically suited to direct application to lead substrates, specialised ‘lead’ mastic sealants (sometimes known generically as roof mastic sealants or roofing mastic sealants) are required to ensure good adhesion and no conflict with the surface upon curing. As well as sealing lead efficiently, lead mastic sealants will bond and seal to or on other common roofing and building substrates such as brickwork, clay tiles, metal, timber and stone. Manufactured from silicone and sometimes other materials, lead mastic sealants are perfect for any leadwork repairs, snagging, or as an alternative to standard mortar in lead flashing and lead chases.

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External Marine Sealing
When resistance to sea water is required, specialist, certified marine mastic sealants are necessary. Made from either silicone, polyurethane or newer polymer materials these products are ideal for sealing joints in decking, seating, walls & floors on boats, ships and other marine applications, but marine sealants will also cope well with simple crack repairs and glass remedial works such as sealing around port holes, fixtures & fittings, making the vessel watertight, safe and secure.

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Natural Stone Sealing
Sealing joints in natural stone externally such as marble, granite, limestone, sandstone and other porous & non-porous natural stone can be problematic due to the reaction with the cure systems in many mastic sealants. The spread of oils, causing migratory staining or ‘leeching’ as its sometimes known, into and onto the stone surface and edges not only looks very unsightly but also cases harm to the stone itself! This issue is often over-looked by DIY people when they seal their own natural stone joints, but it’s also more common than you’d expect from trade professionals too, due too lack of knowledge or sometimes lack of care 🙁 We have a huge range of only the highest quality natural stone mastic sealants that guarantee not to bleed into the natural stone or cause unslightly migratory staining that standard silicone sealants usually cause!

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Non-Staining Silicone Sealant
Sealing joints in natural stone externally such as marble, granite, limestone, sandstone and other porous & non-porous natural stone can be problematic due to the reaction with the cure systems in many mastic sealants causing staining. The spread of oils, causing migratory staining or ‘leeching’ as its sometimes known, into and onto the stone surface and edges not only looks very unsightly but also cases harm to the stone itself! This issue is often over-looked by DIY people when they seal their own natural stone joints, but it’s also more common than you’d expect from trade professionals too, due too lack of knowledge or sometimes lack of care 🙁 We have a huge range of only the highest quality non-staining mastic sealants that guarantee not to bleed into the natural stone or cause unslightly migratory staining that standard silicone sealants usually cause!

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Paintable (over paintable) Sealing
We’re often asked if any external mastic sealants are over paintable and the simple answer is usually no, but there does exist some products that are formulated slightly different than most and then thoroughly tested for paintability and do a good job of it! What most people class as ‘mastic sealants’ are usually silicone products and silicones are notoriusly bad for taking a coating of any kind, so most paints will simply bead straight off and not stick at all and if they do, will almost certainly crack and peel with even the slightest movement. There is one single silicone product that somehow manages overpaintablity which is called OTTOSEAL S113

The other option for external over paintable sealants (as mentioned earlier) is to use non-silicone products such as hybrid polymer, modified polymer or modified silane that cure and dry differently and thus will take coatings far better. As there’s multitudes of different paints, varnishes and coatings with entirely different ingredients, in each case, a small test area is haughty advised.

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RAL Coloured Sealing
RAL colours have long been the ‘goto’ in the manufacturing industry for colour-coding for externals and thus a natural progression for matching mastic sealants to the substrates, wether it be frames, floors, walls or fittings & fixtures. As well as stocking a large selection of mastic sealants made especially to exact RAL colours, we also have a specialised colour-matching service (to ANY RAL colour or indeed any other colour from a physical sample)

Here’s what wikipedia has to say about RAL colours: RAL is a colour matching system used in Europe that is created and administrated by the German RAL gGmbH^[1] (RAL non-profit LLC), which is a subsidiary of the German RAL Institute. In colloquial speech RAL refers to the RAL Classic system, mainly used for varnish and powder coating but nowadays there are reference panels for plastics as well. More information can be found here

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Roof Sealing
As technology evolves and materials used for roofs (and fixtures etc relevant to roofing) change, so too does the mastic sealant products! Innovative roof sealing & roof repairing mastic sealants that are compatible with felt & asphalt make them ideal for industrial and commercial roofing work. Wether it be sealing and bonding leadwork or any other type of waterproof joint work on roofs, around chimneys, fascias, facades and more, there’s specialist roofing mastic sealants available from stock.

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Structural / Hurricane / Impact Sealing
When an external joint seal or bond is required for either structural bonding or structural sealing (usually for glazing) We also keep high impact, hurricane tested & bomb-blast grade, structural sealants, approved for use with specialist safety glass & safety window film systems from Pilkingtons and 3M etc. Often these structural mastic sealants are specified for useably by architects as per the manufacturers specification and whilst the products are used in the production of specialist glazing at factory level, structural sealants are often used directly by trade professionals for structural installation and structural remedial works.

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A Comprehensive List Of Our Mastic Joint Sealants By Manufacturer

3C Sealants

3C Sealants is a brand dedicated to high quality, experience-backed mastic sealants from us ‘County Construction Chemicals’ (hence the name, 3C get it? :-)) A hand-picked selection of high quality sealant products, using the very best materials @ great trade prices.

Visit manufacturers website – click here:

Adshead Ratcliffe (Arbo)

ARBO products from Adshead Ratcliffe have been respected throughout the building, glazing & construction industries by architects and contractors alike for many years, with specialist sealant & adhesive products available for marine, automotive and industrial sectors. Although we only carry a select few products in stock here, we can order any others with a fast turnaround.

* Products are ordered in upon orders being received and will take approx. 2-3 x days

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C-Tec CT1

C-TEC specialise in high quality and exclusive problem solving products, which are developed by listening to their customers and what the market demands. Their flagship product CT1 Unique Sealant & Adhesive has reached an almost mythical status in the UK construction industry, with most, if not all, specifiers and end users aware of the product and it’s capabilites.

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DL Chemicals

DL Chemicals, founded in 1936 as a mastic manufacturer, has now become one of Europe’s most successful independent sealant producers. This company has been run by the same family for three generations building up an excellent know-how of the market. We stock their full range of RAL coloured silicones and a selection other specialist products.

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Dow Dowsil (Dow Corning)

New Name, World of Opportunity: DOWSIL™ Product Brand Name Announced for Heritage Dow Corning High-Performance Silicone Building Products. DOWSIL™ Represents The Combined Power of Dow & Dow Corning; Customers can Continue to Rely on Same Trusted Silicone Technologies for Façade Design. We stock the entire ‘premium quality’ silicone sealant 7 series plus many more specialist joint sealants.

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Everbuild

After a phenomenal rise in the sealant manufacturer ranks, Everbuild Building Products Ltd were acquired by Sika AG and as part of this worldwide group, as a partnership, offer a huge range of sealants that are used widely throughout the construction industry. (see also SIKA)

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Fosroc

While sealants account for only a small proportion of the cost of a building project, their performance is vital to the integrity of any structure. You can trust Fosroc’s expert knowledge of joint design and expertise in sealant technology to help you choose the right sealant for your specific application.

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Geocel

Geocel have been providing the construction and industrial sectors with high quality sealants, coatings and associated chemicals for more than a quarter of a century. Geocel is a wholly owned subsidiary of the international paint manufacturer, the Sherwin-Williams Company, based in Cleveland, Ohio, global leader in the development, manufacture and sale of coatings related products.

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Hodgson

Hodgson Sealants, are the largest independent sealant manufacturer in the UK. A family-run business, and have been growing for 50 years, they employ local people at their production facility based in the East Riding of Yorkshire, with their own in-house R&D facility.

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Mapei

Founded in 1937 in Milan, Mapei today is the world’s largest producer of adhesives and chemicals for the construction industry. We stock all colours of their industry-standard, high quality, internal silicone sealant for commercial and industrial use.

Mapei Mapesil AC Silicone

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Nullifire

Nullifire have been, for many years, world leaders in the development of intumescent coatings, and passive fire protection solutions. Now under the renowned and trusted banner of Tremco illbruck, we now have a selection of fully certified, Nullifire branded passive fire protection sealants.

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Otto-Chemie

Over the course of 130 years, Hermann OTTO GmbH, an innovative, medium-sized company for applied construction chemicals, has advanced to become a specialist for sealants and adhesives. We are the premier distributor of Otto Chemie sealants in the UK and carry a vast selection off their product range.

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Repair Care

The Repair Care International wood repair system (aka Windowcare System) is available to purchase in the shop in Chingford or online via Sealants Online. We keep large stocks of Repair Care Dry Seal Putty replacement sealant in both White & Brown.

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Shell

Known the world over, Shell has a solid reputation for high-end quality and perfromance. Formulated from carefully selected components based on rubber-modified bitumen, easy to apply and designed to offer long-lasting protection and waterproofing. This bitumen sealant & adhesive from Shell has been heavily tested and certified to a very high standard.

Shell Tixophalte Wet Seal & Fix

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Sika

In 2010, Sika celebrated its 100-year anniversary. Developing innovative products and solutions and being consistent in all areas of waterproofing, sealing & bonding amongst other applications, have made it possible for Sika to grow throughout its first century. We stock a select range of Sika polyurethanes, silicones and hybrid polymer sealants relevant to today’s industry.

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Tremco illbruck

Tremco illbruck was created from the merger of Tremco’s European Sealant / Weatherproofing Division with illbruck Sealant Systems in September 2005. We stock a selection of their mastic sealants and adhesives in the form of polyurethane, synthetic rubber and bitumen.