A damp patch on a bedroom ceiling starts the same argument in every house: fix the one spot, or finally pay for a whole new roof. Both answers can be right, and both can be an expensive mistake. A repair is the better spend when the covering is sound and the fault is local, such as a cracked tile, a lifted ridge or a failed flashing. Replacement is the better spend when the fault is the covering itself, because patching a worn roof only moves the leak along. What follows are the questions we work through on site, in the order that settles most cases.
Suspect the covering has simply worn out? Our page on when to replace a roof lists the signs outside, in the loft and in the rooms, material by material.
Start with what has actually failed
A roof is a system of parts with very different lives. The covering (tiles or slate) sheds the rain. Under it sits the underlay, a membrane that catches wind-blown water, and under that the battens and rafters that carry everything. Around the edges and openings are lead flashings, mortar beds, valley gutters and the guttering itself. Any one of those can fail while the rest is fine.
That is why a leak is a symptom and not a verdict. Water that appears in a landing ceiling may enter at a chimney flashing two metres away, run along a rafter and drip where the plasterboard is lowest. If the entry point is a perished flashing, the fix is a flashing. If it is a field of tiles that have lost their nibs, the fix is bigger. Repair or replace is only a sensible question once you know which part has failed and how much of the roof shares that weakness.
The tests that point towards repair
Repair makes sense when the fault is contained and the surrounding roof looks healthy. These are the signs we look for before recommending it.
- The damage is confined to a few tiles or slates, and the neighbouring ones are firm, flat and sound when handled.
- The battens beneath are dry and solid, with no dark staining or soft spots around the leak.
- The fault has an obvious cause, such as a branch strike, a slipped slate, a crumbled mortar bed under a ridge or a split in a lead flashing.
- The underlay is intact where we can see it from the loft, without tears, rot or daylight.
- The roof is not far through its working life, so money spent on it will be used.
On a sound roof, a competent repair can last for many years. Re-bedding and mechanically fixing a ridge, replacing a perished lead flashing or swapping a handful of broken tiles are everyday jobs. Typical UK cost guides put a single slate repair at £100 to £250 in labour plus a few pounds for the slate, with access equipment on top if the job needs a tower or scaffold. Against a full re-roof, that is a small sum for a roof that has years left in it.
The tests that point towards replacement
Replacement becomes the honest answer when the covering has reached the end of its working life, or when the repairs needed would cost nearly as much as the job itself. The signs are different from a localised fault, because they appear across the whole roof rather than in one place.
Look first at the tiles. Concrete tiles that have lost their surface granules, crumble at the edges or show a flaking, sandy face are wearing out. Old clay tiles that have gone porous soak up water in winter and spall when it freezes. Slate is different: the stone lasts for a very long time, and the usual trouble is the fixings, not the slate. Iron nails rust through, the slates slip, and the roof looks like it has a dozen small faults when it really has one general one, which is called nail sickness.
Look next at what the repairs are telling you. If a roofer has been up three times in two winters and each visit found a new problem, the roof is signalling that it is failing in many places at once. The same goes for a sagging ridge or a roof plane that has dipped between rafters, which suggests structural movement or rot in the timbers rather than a surface fault. Rotten battens or rafters mean new tiles have nothing sound to be fixed to.
Finally, look at the underlay. Many roofs from before the 1990s have bitumen felt that has dried, split and crumbled, and some older roofs have no underlay at all. When tiles are lifted for a repair and the felt below falls apart in the hand, the covering is only half the problem. Re-roofing allows the whole system to be renewed together, with new battens, membrane and fixings, so the roof is sound from the rafters up.
Where the line falls on the usual house types
The same fault can mean different things on different roofs, so it helps to see how the decision plays out on common local housing.
| What we find | Usually points to | Why |
|---|---|---|
| A few slipped or cracked tiles on a 1990s estate roof | Repair | Localised damage on a covering with life left in it |
| Crumbling mortar under the ridge tiles | Repair | Re-bed and mechanically fix the ridge, no need to touch the rest |
| Slates slipping across the whole slope on rusted nails | Replacement, or a full re-fix | The fixings have failed everywhere, not in one spot |
| Surface-worn concrete tiles with moss and a felt underlay that has split | Replacement | Covering and underlay are both at the end of their life |
| A leaking chimney flashing on an otherwise sound roof | Repair | A lead replacement solves the cause directly |
| Soft, wet battens found during a leak repair | Replacement of the affected area at least | New fixings need sound timber to hold them |
What the money looks like
Costs shape this decision, so it is fair to put them on the table. Typical UK ranges reported by cost guides for a re-roof on a three-bed semi in concrete tile come out at £6,500 to £10,500, while a wider guide covering new roofs on semi-detached and detached houses spans £4,000 up to £13,000. Those are national figures for orientation only, and the fixed quote only comes after the survey, because the real price turns on roof area, pitch, access, how much timber is replaced and whether scaffolding is needed. Our overview of what affects roofing costs sets out each of those drivers, and the figures for smaller jobs are in our guide to roof repair costs.
A useful rule of thumb is to ask what the repair buys. If a repair costs a few hundred pounds and the roof has ten or more years left, the sum is sensible. If the roof needs repairs in several places, each with its own access cost, the combined bill can climb towards a meaningful fraction of a replacement while leaving you with the same worn covering. That is when replacing starts to look cheaper per year of use, and we say so on the survey.
Rules that apply when you replace
Replacement brings some paperwork that a repair does not. The Planning Portal sets a size test for England: re-covering work is normally left alone by building control when it involves under 25% of the envelope of the building and under 50% of the roof itself. Go past that and approval is required, with the insulation across the entire roof possibly brought up to current standards. Weight is the other trigger: a replacement covering at least 15% heavier than the one it replaces also needs approval, with strengthening where the structure demands it, which is worth knowing before swapping slate for concrete tile. Our page on building regulations for roofing work covers when this applies, and where the work is notifiable we deal with that side for you.
It is also worth keeping the age of the roof in perspective. Our guide to how often roofs need to be replaced lists typical working lives by material, and it helps you read the survey against the date your house was built.
How to judge a quote either way
Whichever route a roofer recommends, you should be able to see why. A good repair quote names the part that has failed, shows you a photograph of it and says what the rest of the roof looks like. A good replacement quote shows you the evidence for replacement across the roof, not just the one leak you rang about, and states what is being renewed: tiles, battens, underlay, flashings, fascias and guttering where they are involved.
Be wary of a quote that offers only one answer without any proof. A roofer who says everything needs replacing without showing you the battens, or one who patches every leak without telling you the covering is spent, is guessing in a different direction. A roof that is repaired badly costs you twice, and a roof replaced early costs you the years it had left.
What we do on your roof
Our first visit is the free survey, and the surveyor climbs up rather than guessing from the ground. We check the tiles or slates, the ridge and hips, the flashings, the valleys and the gutter line, and from the loft we look at the underlay, the battens and the rafters. You get photographs of your own roof, so you can see what we saw, and a fixed written quote that follows.
If the answer is a repair, we say so, even when a bigger job would pay us more. If the answer is replacement, we show you why and give you the price for the whole job in writing, with our 10-year workmanship guarantee set out in the paperwork. When the job finishes, the old materials leave with us and the site is left clear. To see what the next step looks like, our checklist of signs your roof needs attention shows what to look for from the ground before you book. When you are ready, call 01256 213956 or send us a WhatsApp, or go back to our main page for the full range of work we do around Basingstoke.
