One slope only
Can you replace just one side of a roof?
The short answer
Yes. A roof is made of slopes, and each can be re-covered on its own. It makes sense when one slope has failed and the other is sound, because you pay only for what needs doing. The compromises are a visible difference in the tiles until the new ones weather, a careful join along the ridge or hip, and the Building Regulations threshold, which a single slope of an even gable roof sits close to.
When replacing one slope is sensible, how it joins the other, and what to weigh against doing both sides together.
Why one slope can fail before the other
Roofs do not always age evenly. A slope facing the worst of the weather, or the one carrying the valley, a chimney, a dormer or a lot of shade and moss, can wear out years ahead of its neighbour. Different coverings on two sides, such as a rear extension roof tied in to the main house, can fail on different timetables as well.
Replacing the worn side and leaving the rest is a perfectly ordinary job, and it is often what the survey recommends. Our advice is to do no more than the fault demands, which can mean one slope re-covered and a small repair elsewhere. Our guide to when to replace a roof shows the signs that decide it.
The picture changes if both sides share the same age and the same weakness. Then doing one side only buys a second scaffold and a second visit in a few years.
The join along the ridge, hip and verge
Three junctions matter. The ridge is the crest line at the very top, where both slopes meet. A hip is the sloped corner on a roof that is not gabled, and the verge is the trimmed side edge above a gable wall. The work has to deal with all of these, and the ridge is the trickiest, as it belongs to both slopes at once.
Either the ridge tiles are lifted and reset along the whole length, or they are replaced at the same time, since the ridge on one side cannot be disturbed without the other. Following the 2014 revision of BS 5534, bedding in mortar is not enough by itself for these tiles, so the new work is clipped or screwed down too.
A neat join also needs the old slope's top courses to be sound, and the flashing, where the roof meets a chimney or a wall, to be sorted. If the line is wrong, you get a leak at the exact place that was meant to be the strong point.
How new tiles sit beside old ones
The most visible issue is appearance. New tiles are cleaner and often a slightly different shade from tiles that have weathered for decades, and the two sides will not match at first. Concrete tiles lose their surface colour over time, and clay develops a mellower tone. If the side you are replacing faces the road, that difference may matter to you.
Where the slopes face different ways, the match matters less, since you rarely see both at once. Where they are visible together, we can talk through options such as a closer colour, reclaimed tiles for the front, or using sound tiles stripped from the back slope on the front.
Sometimes the old covering is no longer made, and a close match is impossible. Our answer on reusing old roof tiles explains how salvage helps. For a street-facing period house, the choice may be to do the whole roof to keep it uniform.
Building Regulations when a slope is half the roof
On a standard gable roof with two equal sides, one slope is about half of the roof. The Planning Portal sets two tests together: under 25 per cent of the total building envelope affected, and under 50 per cent of the roof. A single side of an even gable sits right at that second line, so the sensible approach is to ask the council or a registered building control approver, not to assume.
On a roof with unequal slopes, a hipped roof or a lean-to, the share will be different. Arun's own page lists re-covering among alterations that need approval, so a quick call is worthwhile. Structural work, or a covering at least 15 per cent heavier, would also bring building control in, and the quick call to the council covers that point as well.
Where the work is notifiable we handle the notification for you, and our page on roof replacement describes the wider job.
Cost, scaffold and the sense of doing both
One slope costs less than two, but not half as much. Scaffold has to go up either way, the ridge is dealt with either way, and the visit and set-up cost the same. A typical UK average for a full roof, per Checkatrade's October 2026 guide, is around £8,000, with most between £4,000 and £19,000 depending on the roof. A single slope is a share of that, set by size, access and covering.
That is why the straight answer is sometimes to do both sides while the scaffold is up. If the second slope will need work within a few years, the combined job is usually the better value, and it leaves you with a uniform finish and one set of dates to remember.
We give an honest verdict on the survey: one slope if it is enough, both if the survey shows the second is close behind. Whichever job you pick, the quote that follows the visit is one total, set down on paper.
Related questions
One-slope questions
Will a single new slope look odd beside the old one?
It can for the first few years, because new tiles are cleaner and a slightly different shade from weathered ones. The difference narrows as the new covering ages. Putting the new work on the back of the house, where it is seen less, is the usual way of keeping the front uniform.
Does replacing one side affect my loft insulation?
It can. Insulation at the eaves has to be kept clear of the ventilation path whichever slope is stripped, and if the work crosses the Part L renovation thresholds in Approved Document L, the roof may need an insulation upgrade. We check both on the survey.