RTV Silicone · Fire-Rated Intumescent · Expansion Joint · Part L Airtightness

Specialist Mastic & Sealant Applicators in London

A sealant is only as durable as its chemical composition. We apply industrial-grade RTV silicones and advanced hybrid polymers — not extended mastics — to deliver moisture-proof, fire-compliant, and structurally sound sealing across all 32 London boroughs.

Why Material Chemistry Matters

Why Standard London Mastic Fails in 12–24 Months

The London mastic market is dominated by contractors using extended silicone products — mastics compounded with oil and solvent fillers to reduce material cost. These fillers evaporate post-application, causing visible shrinkage, surface cracking, and the capillary pathways that allow fungal colonisation. The result is a black, peeling joint within two years — and a recurring call-out cost.

We work exclusively with 100% RTV (Room Temperature Vulcanisation) silicones and advanced hybrid polymer systems. RTV silicones cure by moisture cross-linking, producing a permanently elastic, chemically inert seal with zero shrinkage and no pathway for mould, bacteria, or discolouration — regardless of substrate or environmental exposure. For fire-rated and structural applications, we specify products tested to EN 1366-3 and comply with current UK Building Regulations for passive fire protection.

Specialist Services

Mastic & Sealant Application Services Across London

From domestic kitchen and bathroom sealing to large-scale commercial expansion joint and passive fire protection work — we match the correct sealant chemistry to the substrate, environment, and regulatory requirement.

100% RTV Anti-Fungal Silicone — Kitchens & Bathrooms London

We apply industrial-grade RTV silicones for all sanitary, kitchen, and wet-area sealing across London residential and commercial properties. Zero solvent fillers means zero shrinkage, permanent elasticity, and a chemical barrier against fungal colonisation — backed by a lifetime anti-fungal guarantee. Available in bespoke colour-matched finishes to any grout, tile, stone, or RAL reference.

Fire-Rated & Intumescent Mastic London

Essential for London high-rise refurbishments, commercial units, and residential conversions, our fire-rated systems achieve up to 4 hours of fire integrity (EI240) tested to EN 1366-3. Intumescent acrylic mastics expand when exposed to heat above 125°C to form an inert char barrier, preventing the passage of fire, smoke, and toxic gases through linear joints, service penetrations, and compartment lines — in full compliance with UK Building Regulations for passive fire protection.

Expansion Joint & Structural Movement Sealing London

Modern London developments — glass curtain walling, precast concrete facades, large-format brickwork — generate significant structural movement that standard mastics cannot accommodate. We specify low-modulus sealants with 25%+ movement accommodation capability, applied with correct backing rod and joint geometry to absorb thermal expansion, settlement, and wind load deflection without adhesive failure or joint opening.

Part L Airtightness Sealing — London New Builds & Refurbishments

Air leakage through unsealed penetrations and junctions is the most common cause of failed airtightness tests on London new builds and major refurbishments. Following a failed air test, we conduct a systematic sealing survey — identifying all contributing penetrations, service entry points, and construction interfaces — and apply the appropriate mastic or hybrid polymer system to achieve compliance with the required air permeability target before re-test.

Curtain Wall, Glazing & Facade Sealant London

We apply high-performance structural and weatherseal silicones to glass-to-glass, glass-to-frame, and frame-to-substrate joints across curtain walling, structural glazing, and cladding systems. Products are selected for UV resistance, ozone stability, and long-term adhesion to aluminium, glass, and composite substrates — maintaining weathertightness and structural integrity across the full building envelope.

Bespoke Colour Matching — Stone, Tile & RAL References

Standard contractor sealant palettes are limited to a handful of generic shades. We provide precision colour matching against any natural stone, porcelain, ceramic, or RAL colour reference, producing sealant joints that are visually seamless with the surrounding substrate. Correct tooling technique and surface preparation ensure the finish is indistinguishable from the material joint when viewed at normal distance.

Anti-Bacterial & Food-Safe Sealant — Commercial London

For London commercial kitchens, food preparation areas, clean rooms, healthcare facilities, and cold stores, we apply specialist anti-bacterial and food-safe sealants that maintain hygiene integrity under chemical cleaning regimes. Products comply with relevant HACCP and food contact standards, preventing bacterial harbourage in joints where standard silicones would degrade under repeated exposure to commercial-grade sanitising agents.

Acoustic Mastic Sealing — London Offices & Residential

Acoustic mastic seals gaps and penetrations that bypass sound-rated partitions and floors in London offices, hotels, schools, and residential developments. Unlike standard flexible sealants, acoustic mastics remain permanently non-hardening — ensuring the seal does not crack, shrink, or transmit vibration across the structure over time. Applied to partition bases, service penetrations, and construction interfaces as part of an integrated acoustic system.

Sealant System Guide

RTV Silicone, Hybrid Polymer, or Intumescent Mastic — Which System Does Your London Project Require?

Applying the wrong sealant chemistry to a substrate or environment is as problematic as applying none at all. Here is how the three primary systems differ in practice.

100% RTV Silicone

The professional standard for kitchens, bathrooms, wet areas, and any joint requiring permanent elasticity and anti-fungal performance.

Lifetime anti-fungal guarantee
Anti-fungal and anti-bacterial
Zero shrinkage — moisture cross-link cure
Chemically inert — resists cleaning agents
Best heat transfer over UFPermanently elastic — absorbs movement indefinitelyH

Hybrid Polymer Sealant

The modern professional choice for external joints, facade sealing, and applications requiring paintability with the flexibility of silicone.

Fire-Rated Intumescent Mastic

Legally required for penetrations, linear joints, and compartment lines in buildings subject to UK Building Regulations passive fire protection requirements.

Engineering Standard

How Our Mastic Application Standard Compares to Standard London Contractors

The material chemistry, specification process, and compliance knowledge of the contractor applying your sealant determines its lifespan — not the brand name on the cartridge.

Performance Factor	Standard Mastic Contractors	Our Engineering Standard
Sealant Chemistry	Extended silicone with oil/solvent fillers — causes shrinkage and mould	✓ 100% RTV silicone and advanced hybrid polymers — zero shrinkage
Anti-Fungal Performance	Fungal growth visible within 12–24 months	✓ Lifetime anti-fungal guarantee on all RTV applications
Colour Matching	Limited generic palettes — visible joint contrast	✓ Precision matching to any stone, tile, or RAL colour reference
Fire-Rated Compliance	✗ Domestic sealant only — no passive fire protection knowledge	✓ EN 1366-3 tested intumescent systems — up to EI240 (4hr)
Part L Airtightness	✗ Not offered — requires specialist knowledge	✓ Systematic penetration sealing for air test compliance
Expansion Joint Specification	Standard filler applied — no movement accommodation calculation	✓ Low-modulus sealant selected per joint width, substrate, and movement range
Commercial / Clean Room	Not available — domestic focus only	✓ Anti-bacterial and food-safe products for commercial and healthcare
Longevity	12–24 months typical before failure	✓ Lifetime performance on RTV systems — no repeat call-outs

Our Process

How We Deliver a Professional Mastic Application in London

Remote Technical Assessment & Fixed Quote

Call us with details of your project — substrate type, joint dimensions, application environment (wet room, facade, fire compartment), and any compliance requirements. We assess by phone and provide a fixed-price quotation. No site visit required and no costs added on the day.

Substrate Survey & Sealant Specification

On site, we survey the substrate for contamination, old sealant residue, moisture, and surface integrity before any product is opened. We confirm the correct sealant chemistry — RTV silicone, hybrid polymer, intumescent, acoustic, or food-safe — based on the confirmed substrate and environment, not a generic default.

Existing Sealant Removal & Surface Preparation

Old or failed sealant is fully removed using mechanical and chemical methods. Substrate surfaces are degreased, dried, and primed where required for the specified sealant system. Masking tape is applied to protect adjacent surfaces and ensure a geometric, clean sealant line. No new sealant is applied over old product — a common failure point in standard contractor work.

Professional Application & Tooling

Sealant is applied at the correct gun pressure and joint fill ratio, tooled within the manufacturer’s open time to ensure full substrate contact and a concave, sealed profile. Corners are mitred, ends finished, and all masking removed before the sealant skins. A sealant that is not correctly tooled is not properly sealed — regardless of the material used.

Inspection, Documentation & Aftercare

All joints are inspected for continuity and adhesion before protective coverings are removed. For fire-rated applications, product batch numbers, specification references, and installation details are documented for your compliance records. Aftercare guidance is provided for all domestic and commercial applications.

Frequently Asked Questions

What is the difference between RTV silicone and standard extended mastic?

Standard mastics contain oil and solvent fillers that evaporate after application, causing visible shrinkage, cracking, and the pathways that allow fungal growth within 12–24 months. RTV silicones cure by moisture cross-linking with zero fillers — producing a permanently elastic, chemically inert seal with no shrinkage and a lifetime anti-fungal performance.

Can you match the mastic colour precisely to my tile, grout, or stone?

Yes. We provide precision colour matching to any natural stone, porcelain, ceramic, or RAL colour reference — far beyond the generic palettes offered by standard contractors. When correctly applied and tooled, the sealant joint is visually indistinguishable from the surrounding substrate.

What fire rating do your intumescent sealant systems achieve?

Our fire-rated and intumescent systems achieve up to 4 hours of fire integrity (EI240), tested to EN 1366-3 and compliant with UK Building Regulations for passive fire protection of linear joints, service penetrations, and compartment lines.

What is Part L airtightness sealing and do I need it?

Part L of the UK Building Regulations requires new builds and major refurbishments to meet minimum air permeability targets. Unsealed penetrations and junctions are the most common cause of failed air tests — we systematically seal all contributing interfaces to achieve compliance before re-test.

How long does professional RTV mastic last compared to a standard contractor?

Standard extended mastics show shrinkage, discolouration, and fungal growth within 12–24 months. Our 100% RTV silicone applications carry a lifetime anti-fungal guarantee and remain permanently elastic — requiring no repeat call-outs for the life of the substrate.

How do I get a fixed mastic quote without a site visit?

Call us directly with your substrate type, joint dimensions, and application environment. We provide a fixed-price quotation by phone — no site visit and no additional costs added on the day.

Get a Fixed Mastic Quote — Call Us Directly

Tell us your substrate, joint type, and application environment. We provide a fixed-price quotation by phone — no site visit, no guesswork, no costs added on the day.

Phone Quote

Call Direct

Fixed-price quotation by phone — dimensions + subfloor type + material is all we need