New flat roofs & full roof replacement

There is a point where repairing a flat roof stops being sensible. Once the deck has softened, insulation is waterlogged, or water has been finding its way in for more than a season or two, money spent on patching is money spent twice. A full replacement resets the clock — and it is the right moment to deal with the things that caused the failure.

What a full replacement actually involves

A replacement is not simply a new covering screwed over the old one. We strip back to the joists, inspect the timbers and replace anything that has softened, then rebuild the roof from the deck upwards:

1. Strip-out and disposal — old covering and failed decking removed and disposed of correctly.
2. Timber renewal and firrings — new or repaired joists, then firrings to create a proper fall so water cannot stand on the finished roof.
3. New deck — typically 18mm exterior-grade ply or OSB, fixed and mechanically fastened.
4. Insulation — specified and fitted to meet current building regulations, with vapour control where required.
5. Membrane — torch-on felt or liquid system, with all upstands, outlets and junctions detailed by hand.
6. Trims, outlets and finishes — new drip trims, outlets and, where needed, fascia and guttering repairs.

You receive photographs of the roof at each stage, including the parts that are covered up once the job is finished — a useful record for insurers and future surveys.

Getting the drainage right the second time

Most flat roofs we replace failed for a reason that has nothing to do with the membrane: no fall, too few outlets, or a flat section nobody noticed behind a parapet. Rebuilding without correcting that simply guarantees a repeat in a decade.

Because we are installing new firrings, we can put the fall back into the roof — typically a minimum of 1:60 for felt and 1:80 for liquid systems, with the outlets sized to the roof area rather than to whatever happened to be there before. Where the building allows, we will also add a secondary outlet, so a single blockage cannot flood the roof.

This is also the stage at which insulation upgrades pay for themselves. Bringing the roof up to current standards reduces heating loss through the largest uninsulated surface most buildings have.

Timing, access and living with the work

Most domestic replacements take two to five days on site, weather permitting. Scaffolding, if required, usually goes up the day before and comes down promptly once the membrane is finished.

If the flat roof covers a room you use every day, we will tell you honestly what to expect: which days will be noisiest, when power to any external fittings will be interrupted, and how we will keep the weather out overnight. Our priority is always that the building is watertight before we leave site each day.

For commercial clients we programme around your opening hours, and can work in phases so that part of the roof remains in service throughout.