Terrace Waterproofing in Kendal

The Problem

This second-floor apartment in a modern Kendal development has a 15m² roof terrace accessed from the living room through sliding doors. The terrace was originally waterproofed with a single-ply membrane beneath porcelain paving on pedestals. After 8 years, the membrane had been punctured in several locations — likely during the original paving installation — and water was entering the apartment ceiling below. The property management company had attempted repairs by lifting paving sections and patching the membrane, but the leaks persisted because the damage was widespread and the patches were failing to bond to the deteriorating membrane. The apartment owner was facing a £4,000 ceiling replastering bill on top of the waterproofing repair costs. They wanted a permanent solution that would also improve the terrace's slip resistance, which had been poor on the smooth porcelain tiles when wet.

Our Solution

We removed all porcelain paving and pedestals, stripped the failed single-ply membrane, and inspected the concrete deck beneath. The deck was structurally sound with adequate falls to the two drainage outlets. After repairing minor surface defects, we applied a three-coat liquid waterproofing membrane with polyester fleece reinforcement in the first coat. The liquid membrane — a polyurethane system specifically designed for walkable terraces — conforms perfectly to every surface detail and creates a completely seamless waterproof layer. The final topcoat was broadcast with aluminium oxide anti-slip aggregate before curing, providing excellent grip in all weather conditions. The aggregate surface is attractive enough to use as the finished floor without the need for paving on top — reducing weight and eliminating the risk of membrane damage from pedestal supports. New stainless steel drainage gratings were installed over both outlets, bonded into the membrane.

The Result

The terrace is now completely watertight with a seamless membrane that has no joints, seams, or penetrations across the entire walking surface. The anti-slip aggregate finish provides confident footing even in wet conditions — the owner now uses the terrace throughout winter for the first time. Without the heavy porcelain paving, the terrace feels more spacious and the structural load is significantly reduced. The apartment ceiling below has been replastered and there has been zero water ingress since completion. We provided a 20-year guarantee on the terrace waterproofing system.

Polyurethane Liquid Waterproofing Membrane

The terrace membrane is a two-component polyurethane system specifically formulated for walkable roof terraces and balconies. It cures to form a tough, flexible rubber membrane with excellent abrasion resistance for foot traffic. The three-coat application achieves a minimum 2mm cured thickness that bridges minor substrate cracks while maintaining full waterproof integrity under pedestrian loading.

Polyester Reinforcing Fleece

The 130g/m² polyester fleece in the first coat provides tensile reinforcement that prevents the membrane from cracking over substrate joints or hairline cracks in the concrete deck. The fleece is particularly important at the upstand-to-deck angle where thermal movement concentrates stress.

Aluminium Oxide Anti-Slip Aggregate

The aggregate broadcast into the wet topcoat provides a slip resistance rating of PTV 65+ (Pendulum Test Value), exceeding the 36 PTV minimum required for external walkways. The aluminium oxide particles are extremely hard and durable, maintaining their anti-slip properties under years of foot traffic on this walkable terrace.

Stainless Steel Drainage Gratings

The terrace outlets were fitted with 316-grade stainless steel gratings that sit flush with the membrane surface, allowing water to drain while preventing debris blockage. The grating flanges are bonded directly into the liquid membrane during application.