Should You Repair or Replace Your Roof? A Renovation Expert’s Guide to Replacing a Roof

What are the clear signals that your roof needs replacing? 

The most common reason for re-roofing is the deterioration of the covering or its fixings, with the causes varying by material. Physical damage, provoked by wind, falling trees or even careless walking (possibly by the trades who are up there patch-fixing) can require partial re-covering. Occasionally, it’s the supporting structure that fails – this is typically as a result of water ingress due to lack of regular maintenance. In such cases, even if the covering is still in reasonable condition, it will probably have to be removed to enable repair of the overall roof structure.

This roof was stripped of poor quality cement tiles (inset), with new felt and battens fitted ready to accept reclaimed slates, fixed using copper nails

Unfortunately, problems can also result from misguided work carried out in the past. Concrete tiles are sometimes specified as a low-cost alternative to slate – but they’re much heavier and can overload the structure. In some cases, if the covering has been replaced using a different material, you may simply want to reinstate the original for aesthetic reasons and to enhance your home’s character.

Closed-cell spray foam insulation, applied beneath a roof, can damage both the structure and covering, sometimes necessitating full replacement. Even open-cell spray foam can cause issues; some mortgage lenders may refuse to offer finance unless the work was done by a certified installer with an insurance-backed warranty.

Do you need planning permission to replace your roof? 

Replacing a roof covering like-for-like does not usually require planning permission. That said, changing the covering from one material to another, altering the roof line or changing details at the verges, eaves or junctions might trigger the need for an application.

Adding elements such as dormers, or making changes to enable occupation of the roof space, will need consent. If the house is in a conservation area, the likelihood planning permission will be required is much higher. If you’re dealing with a listed building, then you will need to seek the right consent for any work that cannot be classified as a repair.

Do you need approval from building control for a roof replacement? 

Building Regulations approval will usually (but not always) be required for roofing work. The regs define the roof as a thermal element, which means it should comply with insulation requirements. If you are replacing more than 25% of the covering, then you must upgrade the insulation to satisfy regulations.

The easiest method is to add ample loft insulation over the ceiling structure below (the loft floor). In habitable roof spaces with a warm roof construction, additional insulation may be needed within the roofline. Many homes fall somewhere in between, featuring vaulted upper floors with partially sloping ceilings, requiring a combination of both approaches.

If work has to be carried out to the structure, or more than 50% of the covering is being replaced, Building Regulations will apply to the whole job. If in doubt, contact the local authority for advice. You can secure Building Regs approval through the council or via a licensed independent inspector. There is also a competent roofer scheme, which allows members to self-certify the work they carry out (you’ll get a certificate of compliance on completion).

Standing seam metal roofing can look fantastic on heritage barn conversions – here, Pagurek’s bespoke roofing is complemented by steel Krop guttering in the same RAL colourway for a rural-inspired finish

Should you upgrade your roof insulation as part of the project?

Regardless of Building Regulations requirements, upgrading insulation during roofing work is a smart move. A substantial amount of heat is lost through the roof, making this an ideal opportunity to improve thermal efficiency. For warm roofs or vaulted upper floors, retrofitting insulation later is far more challenging.

Straightforward cold roofs are easy to upgrade, but it’s not a pleasant job, and access to awkward parts of the roof space will be easier when the covering has been stripped. It is also possible to add insulation to the roof line, converting a cold into a warm roof. However, I would not advise this unless you intend to convert the roof to living space in the near future.

Here a new self-supporting roof is being thrown over the historic rafters to protect and retain the surviving fabric

Cold roofs with good ventilation have less risk of mould growth and decay. On this note; it is essential that there is adequate, good cross ventilation. This is even more important in the insulated elements of the structure associated with warm roofs or vaulted ceilings.

How easy is it to convert the loft while repairing the roof?

When major work like this is being carried out, there’s an opportunity to incorporate modifications that would make possible future alterations easier and more affordable. The most likely project, of course, is converting the roof space to create additional accommodation. If this is on the cards for you, then ask your roofers to incorporate counter battens beneath the new covering. When you add your insulation for the loft conversion, the counter battens will ensure a void is left for adequate ventilation.

If you’re already sure you want to convert the loft into habitable space in future, then it would be worthwhile to actually fit the insulation in the roofline at this stage. You might even want to consider installing rooflights now, too.

How much does it cost to replace each roof covering? 

The amount of work involved in re-roofing is enormously variable, so it is not possible to give a truly reliable indication of how much it’s likely going to cost. As a rough guide, it would be reasonable to expect the price of the full recovering of an average-sized roof to be around £15,000. Details, such as valleys and dormers will all add to the cost.

On this like-for-like replacement roof project on a Victorian rectory, original tiles were salvageable and incorporated alongside heritage-style units from Dreadnought Tiles

Materials also vary in price, from £120 per m² for the cheapest concrete tiles, to £300 per m² for good quality slates or clay tiles. Stone slates are very geographically specific and few quarries are still in operation, so often only reclaimed material is available, at a significant cost.

Top of the price range is thatch, which is likely to be well into the £10,000s for a full roof. Any structural repair, insulation upgrade or additional work towards future conversion will represent a notable increase on these ballpark costs.

Case study A cottage in Aberdeenshire upgraded with corrugated metal

The owners of this unlisted cottage in Aberdeenshire consulted Hyve Architects to extend the main floorplan and repair the two existing dormer extensions. They took inspiration from traditional local architecture and the untamed surroundings to create this stunning house.

Photo: Hyve Architects

Combining the original tiles with bright red corrugated metal allowed the new work to read as a contemporary addition. Hidden downpipes and gutters help create a sharp finish, while the simple corrugated profile adds a utilitarian feel, referencing nearby agricultural buildings.

Photo: Hyve Architects

Keen to keep their carbon footprint down as well as pay tribute to their location, the homeowners sourced sustainable materials from Scottish suppliers and contractors wherever possible.

Which roofing material is right for your re-roofing project?

Unlike the structure, the covering has a limited lifespan. Exposed to the elements with no protection, it’s continually under attack from factors including rain, sun, wind, frost, biological agents and pollutants. These affect different materials in different ways and to varying extents.

Both the covering itself and the fixings are subject to deterioration and must be assessed. Maintenance is essential, because even small leaks can cause very serious damage to the underlying structure over time. The extent to which each type of covering can be repaired varies, but all will ultimately need replacement at some time.

Stone tiles

This is the most long-lived traditional option. Many stone tiles can last indefinitely; it’s the fixings and battens that are likely to eventually degrade to the point where repair is necessary.

Total replacement is unlikely to be required, but it might be necessary to strip and recover. In this instance, most tiles can be saved for reuse, but some will inevitably need replacement. This can be difficult in certain areas as many quarries have now closed.

Slate tiles

Slate also has a long lifespan but, because the units are generally much thinner than stone tiles, they are more subject to physical damage and failure, caused by natural flaws. Patch repairing of damaged slate roofs is often a viable option for extending their life because it’s a fairly homogeneous material and easily sourced. As with stone, deterioration of the fixings and battens will eventually lead to recovering. Slates in good condition can be reused, but a reasonable proportion will have to be replaced.

Levitate Architecture and Design Studio chose Cupa Pizarras’ CUPA 12 slate roof tiles for this home in a conservation area. The traditional feel of the slate helped with planning permission, with a sleek finish that sits well on the steep pitched roofs and overhanging eaves

Clay tiles

Clay tiles have a limited lifespan. The main culprit is frost, which can cause them to blow apart. Failure rate varies according to quality, design and roof orientation, degree of exposure and changing weather conditions. Recent winters, with frequent cycling between wet and freezing weather, have been particularly hard on these materials.

Over the lifetime of a clay tiled roof, regular patch replacement with well-matched units will be necessary. Eventually the whole covering will need to be removed and new units laid. Previously used tiles can only occasionally be saved for reuse; even if they appear to be in good condition, much of their viable lifespan has already expired.

Thatched roofs

Despite its reputation as a short-lived option, a properly thatched roof can in fact last for in excess of 60 years. This is very variable, however, depending on location and degree of exposure. This material is subject to decay caused by insects and mould, so the wetter it gets and the more restricted its ability to dry out, the shorter its lifespan.

Periodic repair is necessary to maximise its durability. In particular, the ridge requires regular replacement; limited areas of deterioration can be patched by a skilled tradesperson to delay the need for a full re-thatching.

A re-thatching project nearing completion. There are relatively few master thatchers in the UK nowadays, and their skills are highly valuable, so installed prices tend to be higher than most pitched roof coverings

When the point has been reached where re-thatching has become necessary, usually only the topmost layer needs to be stripped and replaced. In very old roofs, the base coat might still survive from its original construction. This is a precious resource incorporating a wealth of important archaeological information, so if it remains, then you should always look to preserve it.