Flat Roof Replacement questions answered in plain English

A kitchen extension of 25 to 40 m² costs €3,000 to €6,500, a single garage €1,800 to €5,200 and a porch or dormer €1,800 to €2,800. The cost guide breaks it down by size, material and county.

EPDM is one sheet with no seams on most house roofs and needs no flame. GRP is hard and can be walked on. Felt costs least and lasts least. See EPDM vs GRP vs felt.

One to three days on most house flat roofs, weather allowing. See how long it takes.

Often, yes. One fault on a sound roof is a repair: €250 to €900. If the deck is soft or the roof leaks in several places, it's a replacement, and the company will say so.

The old covering comes off one section at a time, and only as much as can be covered the same day. The room below is protected and the roof is covered at the end of each day.

SEAI's roof insulation rules count flat roofs, so insulating one as a warm roof can be part of a roof insulation grant. There's no grant for the membrane alone. Apply before any work starts.

Ask for the roofer's workmanship guarantee and the membrane maker's guarantee in writing: who gives each, for how long, and on what.

One flat roofing company that covers your county. One company only, not a list.

Over-boarding an old felt roof traps any damp already sitting in the timber deck or wet glass-wool insulation underneath, which accelerates dry rot and joist decay. Stripping back to inspect the joists and fitting a dry OSB3 deck or warm-roof build-up is the reliable long-term fix.

A warm flat roof puts 120mm to 150mm of rigid PIR insulation above the structural deck over a sealed vapour control layer, keeping the joists at room temperature and eliminating condensation risk. A cold roof puts insulation between the joists and relies on a 50mm ventilated cavity that is often blocked by adjacent house walls.

Adding a vapour control layer, 120mm to 150mm of PIR insulation and an upper deck raises the finished roof level by roughly 140mm to 170mm. Where a first-floor window sill or balcony door threshold sits too low for that extra height, a hybrid build-up or higher-performance vacuum/phenolic board is used.

Single-piece EPDM rubber typically lasts 40 to 50 years, GRP fibreglass lasts 25 to 35+ years, and two-layer SBS torch-on mineral felt lasts 20 to 25 years. The best choice depends on whether the roof has complex roof lanterns and pipes (suiting GRP or SBS felt) or a clean rectangular span (suiting EPDM).

During the strip-and-replace, tapered timber firing pieces (cut from 50mm down to 12mm) are fixed along the top of the joists, or tapered PIR insulation boards are laid above the deck, creating a positive 1:40 fall toward the gutter.

Yes, domestic flat roof replacement and repair on residential properties in Ireland is billed at the 13.5% reduced VAT rate provided the ex-VAT cost of materials stays below two-thirds of the total job price.