Question answered
Should you re-roof before a loft conversion?
The short answer
Yes, if the roof is old or worn, re-roof before the conversion or as part of the same project. A conversion cuts into the roof for windows and dormers, adds insulation and puts a habitable room under the covering, so a later leak costs far more to put right. Planning, Building Regulations and escape rules all influence the order, so settle the design first.
If the roof is tired, re-roofing first or in the same project is usually the sensible order. The conversion then starts beneath a covering that will stay dry for years.
Why the order of the two jobs matters
A converted loft turns a dusty void into a bedroom or study, with plastered ceilings, a new floor and insulation packed against the rafters. If the roof then leaks, the water lands on finished rooms rather than old suitcases, and reaching the fault means pulling decoration apart. Renewing the covering first, or alongside, avoids that.
Doing both together has practical benefits as well. The scaffold goes up once, the covering is stripped once and new roof windows are fitted into the new roof as it goes on. Flashing kits are set into fresh battens and underlay, so each junction is built properly instead of retrofitted. A covering that will need renewing before long is going to cost you anyway, and doing it at the outset costs less in disruption than doing it later. What a re-roof quote should cover helps you compare firms before you commit.
Roof windows, dormers and what the planners allow
Most loft rooms need daylight, which means roof windows or a dormer. Roof windows come under Class C of the permitted development rules, and Class C can still apply in a conservation area or the National Park unless an Article 4 direction or a condition removes it. For a window in a side slope the condition is obscure glass in every case; the 1.7 m height only lifts the requirement for it to stay shut.
Dormers are different. Class B rights do not apply on article 2(3) land, which takes in conservation areas and the South Downs National Park, so permission has to be applied for. A listed house needs listed building consent for anything touching its character. Put the design to the Adur and Worthing planners, or to the South Downs authority if you live within its boundary, before it is fixed, since their view can reshape the scheme.
Escape rules for the new loft room
Fire escape drives the layout. Approved Document B treats a storey more than 4.5 m above the ground differently from a lower one, and a loft room above a two-storey house needs a protected stairway. That stair takes floor space from the rooms below, so it affects the whole house, not just the roof.
On lower houses, with the top floor within 4.5 m of the ground, an emergency escape window can do the job. The document asks for a clear opening of at least 0.33 m2, with height and width each at least 450 mm, a bottom edge no more than 1100 mm above the floor, and a window that stays open without being held. Some roof windows meet those figures and others do not, so check the specification before ordering. Our page on heavier roof coverings also matters, because new coverings and new loads change what the structure can carry.
Insulation and the thermal standard
A conversion brings the roof into the Part L conversation. Table 4.2 of Approved Document L sets 0.15 W/(m2.K) as the limit for a roof element that is new or replaced, 1.4 for roof windows (or Window Energy Rating Band B) and 2.2 for rooflights. If you re-roof and renovate over half the roof surface, or a quarter of the external envelope, an upgrade to the whole element can follow.
In practice that means thick insulation between and over the rafters, a ventilation plan that stops condensation, and a sealed vapour layer. All of this is easier when the roof is already open. The loft converter, the building control body and the roofer should agree who is responsible for each layer before work begins, so nothing is left for another trade to discover. A gap in the plan, such as nobody owning the eaves ventilation, is a classic cause of damp rafters a few winters later.
Planning the sequence with building control
Because the conversion has structural, fire and thermal elements, involve a registered building control approver, or the Adur and Worthing building control team, early. Notifiable work should not start before the application is in. The roof is normally stripped first, in sections, with staying at home during the work arranged in advance, then steel or new rafters go in, then the new covering.
Tell us about any bats or nesting birds you have noticed, as both are protected. We survey the roof, photograph what is wrong with it and give a written quote as one total for the roofing part. After that we agree the order of work with your converter, so each trade knows when the other needs the roof to be weathertight, and who is on site when. The wider picture of the work is on our roof replacement page.
Loft conversion and roof questions
Can the loft conversion go ahead on an old roof if it does not leak?
Sometimes. If the covering, battens and flashings pass a survey and have years left, they may be kept. But opening the roof for windows and insulation often reveals timber and underlay in worse condition than expected. Get the survey before you fix the design.
Does a new loft room mean the whole roof must be insulated to current standards?
New and replacement roof elements must meet the Part L figures, and a large renovation can trigger an upgrade of the whole element. Whether that reaches your house hangs on the design, so ask building control before any insulation is ordered.
Tell us about your roof
Describe what is happening and we will call you back to arrange a visit.
- Photographs of what we find
- A written quote with one total price
- Or call 01903 299063
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