Filler Sealant

About Filler Sealant

Filler sealants are versatile hybrid products that combine the gap-filling capabilities of traditional fillers with the waterproofing and flexibility of professional sealants. Available at MyToolShed.co.uk, these essential building materials are designed to tackle both interior and exterior applications where movement, weatherproofing, and a paintable finish are required. Modern formulations typically feature MS polymer or hybrid technologies that provide excellent adhesion to multiple substrates including masonry, wood, metal, and uPVC, whilst remaining elastic enough to accommodate structural movement without cracking.

Whether sealing expansion joints in brickwork, filling gaps around window frames, or creating watertight seals in bathrooms, filler sealants deliver durable, professional results that withstand the demanding British climate. Most products are supplied in cartridge form for use with skeleton guns, offering controlled application and minimal waste. MyToolShed stocks filler sealants in various colours to match common building materials, with professional-grade options featuring rapid curing times, low shrinkage, and compliance with relevant British Standards.

Applications

Filler sealants are used across numerous trades and projects:

• General Builders – sealing expansion joints, weatherproofing external structures, and filling gaps in blockwork
• Painters and Decorators – filling gaps around architraves, skirting boards, and coving before decoration
• Window Fitters – sealing around frames whilst allowing for thermal expansion and contraction
• Bathroom Fitters – creating water-resistant seals around sanitaryware and shower enclosures
• Plasterers and Renderers – filling cracks and joints where flexibility prevents future cracking
• Roofers – weatherproofing roof penetrations, flashings, and exposed joints
• Maintenance Contractors – quick building repairs preventing water ingress
• DIY Enthusiasts – home improvement projects requiring flexible, paintable gap-filling solutions

Choosing The Right Filler Sealant

Application Location: External applications require UV resistance and enhanced weatherproofing for UK conditions, whilst internal products prioritise low odour and fast decoration times.

Substrate Compatibility: MS polymer formulations offer the broadest compatibility, adhering to porous materials like brick and concrete, plus non-porous surfaces such as uPVC and metal without primers.

Joint Movement: High-movement areas like expansion joints require sealants with 25% movement accommodation or greater to prevent cracking during seasonal expansion and contraction.

Paintability: Verify the product states 'paintable' or 'overpaintable' if decoration is required. Curing times vary from 1-4 hours for water-based paints to longer for solvent-based finishes.

Colour Matching: Choose colours matching your substrate or easily painted options. Common selections include white, grey, brown, and translucent for inconspicuous joints.

Frequently Asked Questions

What's the difference between filler sealant and standard decorator's caulk?

Filler sealants offer superior elasticity and movement accommodation compared to standard acrylic caulks, making them suitable for joints experiencing expansion and contraction. They provide better adhesion across multiple materials and enhanced weatherproofing for external use, whilst decorator's caulk is primarily designed for internal, low-movement joints.

Can I paint over filler sealant?

Most paintable filler sealants can be overcoated within 1-4 hours for water-based paints, though solvent-based paints may require longer curing times. Always check the manufacturer's technical data, and ensure the sealant surface is touch-dry before painting. Thicker applications and lower temperatures extend curing times.

What joint sizes can filler sealants accommodate?

Filler sealants work best on joints between 5mm and 25mm wide. For deeper joints, use foam backer rod to control depth—the ideal depth-to-width ratio is approximately 1:2. Joints exceeding 25mm may require specialist expansion joint sealants for effective long-term performance.