How Long Does It Take to Replace a Flat Roof?

What the work involves

A replacement is more than laying a new sheet. The old covering is stripped, which on a multi-layer felt roof is slow, heavy work. The deck is then inspected, and any boards that have softened or rotted are cut out and replaced. Insulation goes down if the new build-up needs it, followed by a vapour control layer where the design calls for one. Then the waterproof covering is laid, the edges are finished with trims, upstands are dressed up the walls and flashings are fitted. Rainwater outlets and gutters are checked and reconnected.

Each of those steps takes time, and some cannot start until the one before has finished. A deck cannot be covered until it is dry and sound. Resin cannot be laid on until the boards are down. That sequence is why a quoted time is always a range.

What speeds a job up

A small, plain rectangle with a single outlet and a sound deck is the quickest. Rubber sheet is fast on such a roof, because one large piece can be laid and bonded in a short time and there is no cure to wait for. A roof with easy access, where materials can be lifted straight up from the drive, also saves time that would otherwise go on carrying loads through the house or round the side.

Clear working space matters too. If the roof is reached by a gate that is hard to open or a narrow path, the loading and clearing take longer. Cars moved off the drive and access to a power point for the tools make a quiet difference. Our page on fitting a flat roof in winter deals with how the season affects planning.

What stretches it

Hidden deck damage is the usual cause of delay. Boards that look fine from above can be rotten underneath, and the full extent often shows only when the old covering comes off. Replacing a few boards is quick. Replacing the lot, along with damaged joists, adds a day or more. Sagging decks that need new firrings to rebuild the fall also add time, and the fall must be right or the roof will pond.

Complexity is the next factor. Roofs with rooflights, dormer cheeks, several levels, awkward corners or long upstands all take longer to detail than a simple plan. GRP and liquid systems need each stage to cure before the next, so a damp spell can hold them up. Torch-on felt needs dry weather. Our guide to EPDM, GRP and felt sets out the practical differences between them.

Why a quoted time is a range

It is tempting to ask for a fixed number of days, and a roofer who offers one without seeing the roof is guessing. Until the covering is off, nobody knows how much of the deck needs replacing. What we can do is give a sensible range from the survey, flag the parts most likely to change it, and tell you at the earliest moment if the roof under the old covering looks different from what we expected. That is more useful to you than a promise that has to be broken.

Weather and the programme

The roof is open to the weather during the job, so crews watch the forecast, strip only what they can cover in a day, and sheet over the rest. Heavy rain, hard frost or strong wind can stop work for a day. This is not a delay caused by the roofer so much as a decision to protect your house and the quality of the covering. We discuss any changes with you and make the roof watertight before leaving it.

Before and after the roof goes on

The days around the work matter as well. Scaffold or a platform may need to go up the day before, and a delivery of boards, insulation and rolls arrives ahead of the start. Afterwards, any final checks, snagging, and clearing of the site take a short while. Where the work is notifiable under the Building Regulations, the inspection also needs to be booked. We handle that side. Our article on how much a flat roof costs explains how access and time feed into price.

The free survey gives you a specific estimate for your own roof, with photographs, and the fixed written quote that follows states the work. We set out the order of the job so you know when the roof is open and when it is sealed. Each finished roof comes with our 10-year workmanship guarantee, and the site is left clear. Have a look at flat roofing in Basingstoke for the full list of systems.