Guidance for re-roofing projects

There are many reasons for considering reroofing your home. It could be to

• replace a flat roof or old roof tiles
• change or add roofing as part of an extension project
• install something new on the roof, such as a roof window or solar panels

In all these cases, you will need to check whether building regulations approval is necessary.

When building regulations approval is required

As a general rule, if you’re reroofing 50% or more of the roof area, or if elements such as insulation or ventilation are being changed, building regulations approval will be required.

You can apply to us for Building Regulations approval to us or you can use a roofing contractor registered with the National Federation of Roofing Contractors Ltd (NFRC). Roofing contractors that are members of the NFRC’s ‘Competent Roofer’ scheme can self-certify their own work.

Please bear in mind that without approval, you will also not have the certificates of compliance, which will be necessary to sell the home.

Make a Building Control application

If you’re re-covering or carrying out repairs to less than 50% of your pitched or flat roof, it’s unlikely that you will need to inform us. Consent is not normally required as long as no changes are made to the structure of the roof and you replace the roof finish like for like (i.e. slate with slate, not concrete tiles) and affect no more than 50% of the roof area at any one time.

It’s a good idea to check with us first, your local authority Building Control Team, if you aren’t sure. We’re always happy to discuss individual situations.

Planning consents

Normally re-instating roof coverings on a like-for-like basis will not require planning consent. But if you want to change the type of materials, or raise the profile of the roof, a planning application may need to be made.

‘Part L’ of the Building Regulations requires you to improve thermal efficiency where you’re renovating significant areas of the building’s ‘thermal envelope’ (i.e. the roof, main walls or floors). This is something that commonly affects flat roofs because they need re-covering more frequently than main roofs.

Get pre-application planning advice

Other permissions

Depending on the specifics of the reroofing project, other permissions and approvals may also be required. For example, if bats are living in the roof, a protected species survey may need to be carried out, and a license to do the work may be required.

Assessing the condition of your roof

When it comes to assessing the condition of roofs, a good rule of thumb is to take a good look down the street at nearby houses of the same age – if a lot of these have new roof coverings, there’s a greater chance that yours may also need to be re-clad in the not too distant future. If a roof is leaking or has the odd missing tile, it may simply need some localised maintenance, rather than complete re-covering. Probably the most common cause of leaks is from defective flashings at junctions, such as to chimney stacks. Flashings are best made from lead or failing that from modern GRP. Mortar fillets are very prone to cracking and best replaced.

Valleys where roof slopes meet are another weak point and need to be cleared from time to time of accumulated leaves and debris. It should be a straightforward task for a roofer to re-fix the odd slipped or missing tile or replace any that are cracked. Many older roofs show signs of historic settlement, but if the structure is satisfactory and there’s no leakage, this can often be acceptable. However, it’s also not unusual for some localised re-pointing to be required to the ridge tiles running along the top of the roof where mortar joints have eroded, and also to verges at the edge of roof slopes.

Popping your head into the loft can tell you a lot about the wellbeing of the property. Roof spaces should be well ventilated and are meant to be cold and draughty above the layers of loft insulation because good ventilation helps disperse any damp. Most properties built in the last 60 years have a layer of underfelt beneath the tiles as a secondary barrier against the weather. One thing to check in older terraced and semi-detached properties, is whether the firebreak party walls are in place – as these were sometimes omitted when originally built. If they are missing, they will need to be built up in lightweight concrete blocks or fire-resistant plasterboard.

Roof coverings

On older properties it’s often the fixings that fail first, for example many old slate roofs suffer from corroded nails. The good news is, it’s often possible to salvage and recycle the original slates or tiles and re-fix them.

When complete re-cladding is required, re-instating the original tile or slate coverings is normally the best option. Traditional natural slates or clay tiles found on older buildings have a much longer lifespan than today’s manufactured concrete tiles, but they are more expensive. However, some types of modern composite fibre slates and tiles are designed to look similar to the real thing and can be a cost effective alternative.

Flat roofs

Felted flat roofs are notorious for having short lifespans – sometimes lasting as little as 10 years before needing re-felting. Fortunately roofing felt is relatively cheap to install. Other materials such as artificial rubber (EDPM) and fibreglass should last longer than felt, and lead sheet is best of all, but is far more expensive.

Upgrading insulation

You’ll want to ensure that when your home is reroofed that insulation is adequate. It is likely on the majority of reroofing projects that insulation will need to be upgraded and as a result of this, it may also be necessary to incorporate increased cross-ventilation measures, such as: eaves ventilation, tile vents and ridge vents.

Building Regulations require that insulation is upgraded when roofs are both re-decked and re-covered. The best way to do this is to strip off the old defective felt, replacing or retaining the existing deck depending on its condition, then lay a new layer of rigid insulation boards on top of the deck, before applying the new roof covering. This creates what is known as a ‘warm roof’ but means the height is raised slightly with consequent detailing issues at junctions.

Alternatively, insulation can be laid above the ceiling below between the joists as a ’cold roof’, but you need to allow at least 50mm ventilation space above the insulation and this will need to be ventilated on opposite sides of the roof. Flat roofs must be laid to a suitable angle or ‘fall’ so the rainwater can discharge into the guttering, and care must be taken to ensure junctions at upstands etc. to adjoining walls are watertight. A surface layer of reflective stone chippings is often applied to protect the roof from the effects of UV sunlight.

Access and safety

Falls from height are responsible for many serious and fatal injuries every year. The Working at Height Regulations are designed to prevent such injuries and apply to work carried out two metres or more above ground level. Scaffolding is normally required for roof work and needs to be erected by a ‘competent person’. Ladders are only acceptable for access or work of short duration. Other types of access equipment include mobile elevated platforms and scaffold towers.

Checking a roofing product's guarantee

You should also be aware that whilst it is good to see the advances in roofing products on the market today, you should always check that the product you intend to use is not part of a total system which manufacturers won't guarantee unless installed to specific instructions. The last thing a Building Control Officer wants to do is come along after the work has been done and tell you it is not satisfactory.

Further information

Thermal elements are described in approved document L1B (domestic) of the Building Regulations on the Planning Portal website. When your roofing contractor is undertaking reroofing, it is recommended that they follow the guidance below:

Reroofing on the Planning Portal

The Building Regulations (England and Wales) define the requirements for approval.