Roof renovation: putting the whole roof right in one go

A re-roof replaces what is on top of the rafters. A renovation also asks whether the rafters, purlins and wall plates are doing their job, whether the roof has spread and pushed the walls outwards, whether the loft is ventilated, and whether the insulation, fascias, soffits and guttering should be renewed at the same time. It is typically a job for houses that have not had serious roof work in living memory, for a house bought as a project, or before a loft is used for storage or living space.

The advantage is one scaffold, one programme and one set of details designed to work together. Ventilation at the eaves, the new underlay and the insulation, for example, have to suit each other, and they rarely do when they were installed by three different firms years apart.

The roofer, and for older or altered roofs a structural engineer, should inspect the loft as well as the outside. Typical findings are purlins that have deflected, struts removed by a previous owner to make storage space, rafters notched for cables, water staining around chimneys and valleys, and signs of woodworm or rot at the wall plate. On a terrace, the state of the party wall in the loft and the fire-stopping above it matter too.

Ask for the findings in writing with photographs. That record lets you separate essential structural repairs from improvements you might choose, such as replacing plastic fascias or adding roof windows. It also lets Building Control or the competent person scheme see what was found and what was done.

Structural repairs to a roof need Building Regulations approval and should follow an engineer's design. Common work includes doubling up weak rafters, adding or restoring struts and binders, fixing roof spread with ties, and replacing rotten wall plates. Removing or cutting a structural timber without that design can cause movement and cracking in the walls below.

Because a renovation affects most of the roof, the insulation has to be improved where it is practical to do so. Two approaches are common. A cold roof keeps the insulation on the loft floor and ventilates the roof space above it. A warm roof places insulation along the slope, between and over or under the rafters, so the loft stays within the heated envelope. The right choice depends on what the loft is used for and on how the roof will breathe.

Spray foam applied to the underside of the roof deserves care. Government-commissioned research found moisture and timber decay risks in some combinations of foam, underlay and climate, with the highest risk where foam is sprayed directly onto the roof covering. If spray foam is already there, the renovation is often the moment to remove it and assess the timbers beneath.

Chimney stacks can be repointed, rebuilt, capped or reduced while the scaffold stands. The same applies to lead flashings, parapet gutters, fascias, soffits and guttering. Replacing fascias and soffits does not normally need Building Regulations approval, but the roof ventilation at the eaves must not be reduced. In a house built or refurbished before 2000, old soffits and undercloaks can contain asbestos, which the HSE says should be identified before anyone cuts or breaks them.

Bats roost in older roofs. If there are signs of them, a bat survey comes first, and work may need a licence and a timetable that avoids sensitive seasons. Leaving this until the scaffold is up is expensive.

Source: hse.gov.uk

A renovation quote is a package, so ask for it broken down. That lets you compare it with the separate costs of a re-roof and make decisions item by item.

• the survey findings the price is based on, with photographs
• structural repairs and who designed them
• covering, underlay, battens and all flashings and details
• insulation method, target standard and ventilation strategy
• chimney, fascia, soffit and guttering work, listed separately
• asbestos or bat surveys, if needed, and who arranges them
• Building Control or competent person certification, scaffold duration and waste

Describe the roof and what you already know about it. We show the job, without your personal details, to roofing businesses near you. Only one can buy it, and once it has, the request is gone from the list. You get an email with that business's name, address and phone number before it receives yours, and the service costs you nothing.

If no roofer takes it within 21 days, the request is withdrawn. You can turn down the quote and seek others. Offrano checks only that the buyer is a registered business, so look at completed roofs and check its scheme membership yourself.