White UPVC Capping Board – 1.25m Long, 9mm Thick (100–400mm Depth Options)

Transform your window sills effortlessly with our premium White UPVC Capping Boards, engineered for high performance, durability, and a sleek finish. These 1.25-metre long, 9mm thick boards are specifically designed to cover and upgrade damaged or outdated timber or MDF sills without the need for removal or costly renovations.

Perfect for window sill renovations in residential and commercial properties, this plastic capping board product is crafted from high-quality exterior-grade UPVC that is fully waterproof, UV-stable, and resistant to warping, cracking or discolouration over time. Whether you’re completing a DIY project or professional installation, our white capping boards offer a low-maintenance solution that enhances any interior.

Each board comes in a full 1.25-metre length for extended coverage, with a robust 9mm thickness to provide extra rigidity and impact resistance. With depth options available from 100mm to 400mm, it’s easy to find the ideal fit for your specific application – from narrow internal sills to wide modern window boards.

Key Product Benefits

• Extra-long 1.25m length – ideal for longer window sills or fewer joins
• Rigid 9mm UPVC – thick, durable, and superior to 5mm budget alternatives
• Fully waterproof – perfect for use in bathrooms, kitchens, utility rooms, and conservatories
• UV-resistant finish – colourfast, fade-resistant surface ensures long-lasting appearance
• Quick and easy installation – trim to size and fix using adhesive or screws
• Wipe-clean surface – no painting, sanding or varnishing required
• Available widths: 100mm, 150mm, 175mm, 200mm, 225mm, 250mm, 300mm, 400mm
• Matching accessories available – end caps, corners, and adhesive sold separately

Ideal Applications

• Covering internal window sills in modern or traditional homes
• Refurbishing rental properties or commercial buildings quickly and affordably
• Protecting existing timber sills from moisture damage
• Improving energy efficiency by sealing drafty old boards
• Quick fixes before property sales or inspections

Technical Specifications

Installation Guide

1. Clean the existing sill surface to remove dust, dirt, and grease
2. Measure and cut the board to the desired length using a fine-tooth saw
3. Dry-fit to ensure proper fitment and trim if necessary
4. Apply a strong grab adhesive such as CT1 or No More Nails
5. Press firmly into place and hold for 60 seconds
6. Optional: add white silicone sealant around the edge for a clean finish

Note: For installations over 1.25m, join boards using a butt joint or dedicated trim connector.

Why Choose Windows4You?

We are a UK-based supplier of UPVC window trims, fascias, soffits and capping boards. Our products are sourced directly from leading manufacturers, ensuring quality, consistency, and availability. With fast delivery, flexible quantities, and expert customer support, we help trade professionals and homeowners complete their jobs with confidence.