Roofers are often asked to pick a side before anyone has looked properly. Better to start with the questions that decide it. How old is the covering, and in what state? How much of the roof has failed, and where? What is the underlay and the batten line doing underneath? What would each route cost over ten years? Does the work cross a threshold in the Building Regulations? And are you selling soon?
This guide is a framework for that weighing, not a list of warning signs; for the signs themselves, see when a Stroud roof needs replacing. Nothing here is a promise about your roof. The decision is made at a survey, with photographs, and the written quote follows. The whole service is described on our roof replacement page.
Start with age, then correct it for condition
Age is the first filter, but a poor one on its own. Typical lifespans in published sources vary widely. MyBuilder's guide gives natural slate as 80 to 100 years or more and clay tiles as 40 to 60 years; concrete tiles run 30 to 50 years on the same page, while Marley's blog puts concrete at around 60 years and adds that the figure carries no guarantee. Cotswold District Council's guidance reckons a well-maintained stone slate roof can easily reach 100 years. These are ranges, and they depend on exposure, workmanship and upkeep.
So treat age as a prompt to look closer. A 40-year-old concrete tile roof with sound battens may have years left. A 25-year-old roof laid on a poor batten line may not.
What condition adds
Condition is what the survey adds. We check whether the covering is flaking or delaminating (shedding thin layers), whether tiles hold their fixings, whether the line of the ridge is straight and the slope flat, and what the underside looks like from the loft. A covering in good order with a few failed pieces is a repair candidate whatever its birth year. A covering that is sound in the middle but crumbling across whole slopes is not.
A roof's age tells you when to look. Its condition tells you what to do.
How much of the roof has failed, and where
Extent matters more than almost anything else. Failures that are local are repairable. Failures that are spread are not, because patching a spread-out fault means returning again and again.
Here is the shape we look for.
- One slope, one area. A cluster of slipped or cracked tiles above a bay window, or a leaking valley, is a contained repair.
- One slope, but the whole slope. If the south-facing side is perished while the north side is sound, replacing one slope can be a sensible middle route. Our page on replacing one side of a roof sets out when that works.
- Several slopes, different places. If failures keep turning up at random across the whole roof, the covering as a whole is at the end of its life.
Repeat repairs
The repair history is a telling sign. One call-out in ten years suggests a contained fault. A repair every winter, each time in a new place, suggests the covering has gone. MyBuilder's repair guide puts minor repairs at £100 to £300, moderate ones at £500 to £1,000 and major repairs at £2,500 or more, so three or four moderate repairs approach the territory of a replacement without ever fixing the cause.
Underlay, battens and the parts you cannot see
The covering is the visible part. The underlay and battens are the working part, and often decide the answer. Underlay is the membrane under the tiles or slates that catches wind-blown moisture and condensation. Battens are the thin timbers nailed across the rafters; every tile or slate hangs from one. They take the weight of the covering and set its spacing, so a soft or split batten undermines the tiles it carries long before the tiles themselves show a fault.
Why they tip the balance
You cannot replace a batten without lifting the covering above it. That makes the repair question tangled: if the battens are rotten across a slope, a tile-by-tile fix cannot reach them. On an older roof with no underlay at all, a covering may be sound but nothing sits behind it to stop dust, snow or driven rain getting into the loft.
Re-roofing gives the chance to fit new underlay and battens in one go, and to ventilate the roof void properly. BS 5250, the code of practice on moisture in buildings, is the basis for the ventilation figures that manufacturers quote. Our guide to re-roofing materials explains the choices at that level.
On a good day, a lifted tile shows us dry timber and a clean underlay. On a bad one it shows black, soft batten ends and daylight. The first points to repair; the second points to a strip.
Ten years of cost, not just this month's invoice
A repair is cheaper now, which is why it is tempting. The fairer comparison is total spend over ten years, including the scaffold you will need each time.
MyBuilder's roof repair guide gives £150 to £1,500 as the average repair range, with storm-damage fixes £500 to £1,500. MyBuilder's new roof guide gives £5,000 to £12,000 for a full re-roof, while Checkatrade sets the average near £8,000. A scaffold for a re-roof is about £1,125 on MyBuilder's figures; a repair that needs scaffold carries a share of the same cost.
| Route | Typical UK cost | What it does not include |
|---|---|---|
| Single repair | £150 to £1,500 | Future repairs elsewhere on the roof |
| Full re-roof | £5,000 to £12,000 | Timber repairs that appear once the roof is opened |
Doing the sum
Write the numbers down before you decide; it takes a quarter of an hour and removes a lot of guesswork.
Count the repairs you have paid for in the last few years, estimate how many more the roof is likely to want, and add the scaffold each time. If the repair route totals more than half a replacement within a decade, replacement starts to look like the better value. If the faults are contained, it does not. Our guide to what a new roof costs sets out the replacement side in detail; the roofing-repair side is on our repairs pages.
Regulations that tip the scale
A repair and a replacement are not treated the same by the Building Regulations. Planning Portal guidance draws the line for a building control application at 25 per cent of the building envelope and 50 per cent of the roof; keep below both and the application is not normally required. Cross either and an application applies, with a thermal upgrade a possibility. A tile repair sits well below those limits. A full strip does not.
That has a cost consequence. Replacing a whole roof can bring in insulation requirements under Approved Document L: when the covering comes off down to the rafters and the roof is rebuilt, the whole element may need to reach a U-value of 0.16 W/m²K. We explain the test in our Part L guide, and the application thresholds in our guide to re-roofing and the 25% and 50% rules.
A heavier covering
The same guidance adds that a new covering which increases the weight by 15 per cent or more needs approval. A so-called repair that exchanges a lightweight covering for a far heavier one is therefore a different job altogether. Should the house be listed, or lie in a conservation area, raise it with Stroud District Council's planning officers before ordering anything.
None of this should push you towards replacement. It should push you to know the line, and to see whether the repair you are considering sits comfortably on one side.
Selling, letting or staying put
Plans for the house change the answer. A person who will be in the house for twenty years gets full value from a new covering. A person selling next spring will want a roof that does not appear on a buyer's survey as a problem.
If you are selling
A buyer's surveyor looks at the roof from the ground and in the loft. A roof that has been repaired recently, with invoices and photographs, can be easier to defend than one with a history of patches. Where the covering has little life left, a replacement with a written guarantee is a stronger position, though not always one that the sale price repays. We do not predict that.
Our signs guide lists what a surveyor may flag. A repair done well and recorded properly is not a disadvantage.
If you are staying
Staying on makes the ten-year sum more important and the sale story irrelevant. It also makes timing a factor: a replacement can be planned for a dry spell, where an emergency repair cannot.
For a landlord, the question is similar but with more at stake over a tenancy: a leak in a let property is a repair that cannot wait. Whatever your position, the quote that follows the survey lays each route side by side.
What our survey gives you to decide with
We do not arrive with an answer. For this decision the survey takes in the covering from the ground and, if conditions allow, on the roof slopes; the loft, where we look at timbers, underlay and any daylight showing through; and the gutters, flashings and ridge. Photographs of your own roof come with it, not stock pictures.
The quote that follows covers the work in full. If a repair is the right call, it says so and gives the figure. If a replacement is, the quote covers scaffold, strip, materials, labour, waste and making good, and anything to do with timbers is marked as priced on survey because nobody can price rot they have not seen. Where a middle route exists, such as renewing a single slope, that is priced too, so the three options sit next to each other.
Older properties are dealt with like for like: stone returns as stone and slate as slate. Where building control is involved, we explain the consent that applies and take on the notification. On completion the site is cleared away, and what we did is covered by a 10-year workmanship guarantee given in writing.
Photographs of the problem and the address are enough to start. We will reply with what they show and what would need a visit, so that your decision rests on evidence about your own roof and not on a sales pitch. If the answer is a modest repair and nothing more, you will hear that from us too.