Flat roofs, repaired and replaced
Garages, extensions, dormers and porches. A flat roof is never truly flat, it is laid to a fall, and most of them fail where the water stops moving. All work guaranteed.
Where flat roofs give up first
Flat roofs fail at their edges and their joins, not out in the middle. Water sits where the fall has gone, usually in a low corner or against a wall.
From there it works into the upstand, the part of the covering turned up the wall, or into a lap between two sheets. Once it is under the covering it runs along the deck, the boards underneath. The stain inside can be feet away from the hole.
A flat roof is not flat
Every flat roof is built to a fall so water runs off it. The fall is usually made by firrings, tapered strips of timber laid on top of the joists.
When the deck sags, or the firrings were never right, the water stops moving. Standing water is called ponding, and it is the best single warning that a covering will fail early.
Repair or replace
A small split, a lifted lap or a failed edge trim can be repaired. It is worth doing when the rest of the covering is sound and the deck under it is dry.
Sometimes a repair is money spent twice. That is the case when the deck is soft underfoot, water ponds across the whole roof, or the covering cracks as you press it. We tell you which of the two you are looking at.
How long does a flat roof take to replace?
Less time than a pitched roof, and often without a scaffold on a garage or a single storey extension. The deck has to be dry before anything goes back on, so a soaked deck holds the job up.
Rain stops the work as well, because an open deck cannot be left uncovered overnight. We tell you the likely span when we look at it.
Where this work is covered
Working out of Surrey we cover flat roof work in Crawley, Brighton, Horsham, Reigate, Redhill and Dorking. Outside those towns, ring and ask first.
The extensions and dormers behind the Brighton and Hove terraces are nearly all flat roofed. They sit out of sight until they leak.
How the job goes
What happens when we do your flat roofs
-
01Look at it from above
A flat roof can only really be judged from above. We look for ponding, splits, lifted laps and the state of the upstands and trims.
-
02Press the deck
A sound deck is firm underfoot. Soft patches mean water has been in the boards, and that changes the job from a repair to a new covering.
-
03Say which it is
We tell you plainly whether it is a repair or a replacement, and why we think so. The estimate and the advice are free.
-
04Strip and make the deck good
On a replacement the old covering comes off and the deck is checked over. Wet boards are replaced. Falls are corrected where they have dropped.
-
05Edges and outlet last
Trims, upstands and the outlet into the gutter are detailed last. That is where flat roofs leak, so that is where the time goes.
Common questions
- Is a garage roof different from an extension roof?
- The covering and the detailing are the same. What is underneath is not. A garage roof drips onto a car and gets ignored for years. An extension roof drips onto a ceiling, so it shows up early and costs more to put right inside.
- My flat roof has bubbles in it. Is that serious?
- Blisters mean air or water is trapped under the covering. A few small firm ones on a sound roof can be left alone. A blister that is soft, spreading, or splits when you press it has water in it, and that water is already in the deck.
- Can a new covering go straight over the old one?
- It gets done, and it is usually a bad idea. Going over the top hides a wet deck, adds weight and buries the fall you already had. We would rather strip it off and see what we are working on.
- Why does my garage roof only leak in heavy rain?
- Light rain runs off. Heavy rain fills a low spot faster than the outlet can clear it. The water then sits above a lap or a trim and finds its way under. That points at the fall or the outlet, not at the whole covering.
- Can I walk on my flat roof?
- Only if it was built to be walked on, and most are not. A normal flat roof takes the odd trip up for maintenance, in soft shoes, treading over the joists. Regular use splits laps and dents the deck.
Related work
Roofing advice on this
Plain answers to the questions we get asked most about this work, written before you ask us for a price.
Get an estimate
Tell us what the roof is doing
Estimates and advice are free. Ring and describe the problem, or send a photograph of it, and you will get a straight answer about whether it needs a repair or a new roof.
All work guaranteed.
Want us to take a look at the roof?
Leave a name and a number and we will ring back to sort a time. Estimates and advice are free.