Flat Roof Replacement
Across North Wales
Built To Stay Watertight

EPDM is a single-piece rubber membrane, usually installed in one sheet on domestic roofs so there are no field seams to fail. It is flexible across a wide temperature range, handles building movement well, and has a long service life for the money. It is a strong default for extensions, garages and dormers.

Its weak points are mechanical damage and detailing. Sharp objects and heavy foot traffic can damage it, and every corner, upstand and outlet has to be detailed with the manufacturer's own components and adhesives rather than improvised.

GRP is a seamless glass-reinforced resin laid in situ and cured to a hard, walkable surface. It suits balconies, roof terraces and any flat roof that will be walked on, and it takes crisp trims and edges well.

GRP is weather- and temperature-sensitive during installation and needs a rigid, dry, well-fixed deck; on a bouncy or damp deck it will crack. That is why the deck work is quoted as part of the job, not bolted on afterwards.

Modern high-performance torch-on felt is nothing like the pour-and-roll felt on 1970s garages. Installed as a two- or three-layer system with proper detailing it is durable, economical and easily repaired, which makes it a sensible choice on larger and commercial roofs.

Liquid-applied systems are the answer where a roof has complicated detailing, many penetrations, awkward abutments, plant bases, or where stripping is impractical. They cure to a seamless membrane over almost any shape, and they are frequently the right tool on commercial roofs.

Flat roof decks are typically plywood, OSB or concrete. Timber decks are inspected for softness and delamination and replaced where necessary. Falls are created with firring pieces or tapered insulation: usually a minimum design fall so water runs off even after deflection.

Replacing more than half a flat roof normally brings building regulations thermal requirements into play, which means adding insulation. That can be warm-deck construction, with insulation above the deck under the membrane, or a cold-deck arrangement with ventilation; the survey sets out which applies to your roof and what it means for the finished height at doorways and abutments.

Not every worn flat roof needs to come off. Where the deck is dry and structurally sound, a liquid overlay system gives a new, seamless, fully warranted waterproof layer over the top of the existing covering. The old surface is cleaned, dried and primed, reinforcement is embedded at every joint, upstand and outlet, and the finished membrane is continuous from parapet to parapet.

Because there is no strip-out, there is no skip on the drive, no disposal cost, no open roof overnight and far less disruption to whatever sits below. On commercial roofs it also means trading can carry on underneath while the work is done.

We only recommend an overlay after probing the deck and checking moisture. If the boards are soft or the insulation is wet, the covering has to come off, and we will quote it that way rather than sell you the cheaper option that will fail.

For larger domestic and commercial flat roofs we install three-layer torch-on bitumen systems: a perforated or bonded underlayer, an intermediate reinforcement layer and a mineral-finished cap sheet, each fully bonded and lapped, with all upstands, drips and outlets detailed in matching material.

Three layers is the point. Two-layer work is common on cheap quotes and leaves far less redundancy: with three, a single defect in the cap sheet is not an immediate route into the building. Correctly installed, a three-layer torch-on roof is one of the most durable and easily repaired flat roof coverings available.

A warm roof puts rigid insulation above the deck, directly under the waterproof membrane, so the deck and the structure below stay at room temperature. That removes the cold surface where condensation forms, which is the reason so many older cold-deck flat roofs rot from the inside even when the covering is intact.

Warm roof build-ups also avoid the need for cross-ventilation voids, make it far easier to meet current thermal requirements when more than half a roof is replaced, and noticeably warm the room below: extensions and dormers with flat roofs are usually the coldest rooms in the house.

The trade-off is height. A warm deck adds build-up, so we check door thresholds, window cills, abutment flashings and upstand heights at survey and design the falls, tapered insulation and trims around them before quoting.