A rooflight conversion is typically four to six weeks on site, a dormer six to ten, and a hip-to-gable with a dormer longer again. Add design, structural calculations and approvals beforehand. The roof is opened and made weathertight again quickly — usually within the first week or two — which is the stage most people worry about.
- Most of the work is reached from outside via scaffold, so the house stays usable longer than expected.
- The disruptive week is when the stairwell is cut through the existing ceiling.
- The roof is open for days, not weeks, and is sheeted throughout.
- Approvals and lead times sit before all of this and are often the longer half.
Typical durations
| Type | On site | Notes |
|---|---|---|
| Rooflight / Velux | 4–6 weeks | No change to roof shape; least structural work |
| Rear dormer | 6–10 weeks | The most common conversion |
| Hip to gable | 8–12 weeks | Gable wall built and tied in |
| Hip to gable plus dormer | 10–14 weeks | Both operations |
| Any of the above on a trussed roof | Add 1–2 weeks | Steels and new floor before trusses come out |
| With en-suite | Add around a week | Plumbing, drainage, possibly a pump |
These are on-site durations. Design, structural calculations, planning if needed, party wall notices and material lead times all happen first and frequently take as long again.
The sequence
- Scaffold up. Usually with a dedicated hoist or loading bay, because everything comes in through the roof rather than through the house.
- Structural floor. Steels in, new joists spanning onto them, clear of the existing ceiling below. On a trussed roof this happens before any truss is cut.
- Open the roof and build the dormer or gable. This is the exposed phase, and it is days rather than weeks, with the opening sheeted throughout.
- Weathertight. Roof covering, windows and dormer cladding on. The anxious part is over by this point.
- Stairwell formed through the existing ceiling. The most disruptive moment for the floor below — dust, noise and a hole in the landing.
- Stairs installed, giving internal access for the first time.
- First fix. Electrics, plumbing, insulation, fire protection.
- Plasterboard and plaster, then drying time.
- Second fix and finishes. Doors, including the fire doors to rooms off the escape stair.
- Building Control final inspection and the completion certificate.
Steps one to four happen almost entirely outside the house. That is why a loft conversion is usually less disruptive to live through than an extension of similar value.
What the roof being open actually means
This is the thing people worry about most, and it is a shorter and more controlled phase than the worry suggests.
The roof is not left open to the sky for weeks. The section being altered is opened, the structure built, and it is made weathertight again — typically within days. Throughout that period the opening is sheeted, and the scaffold is designed with that in mind.
Work is planned around the forecast. No competent contractor opens a roof on the morning of a forecast storm, and if the weather turns the opening is closed and the work waits.
What you should ask: how long will the roof be open, what protection is used, and what happens if the forecast changes. A contractor who has thought about it will have specific answers rather than reassurance.
Living through it
Most clients stay in the house, and it is generally more manageable than an extension.
The easy part: while the structure and dormer are being built, access is via scaffold and the work is above your ceiling. Noise, yes, but the house functions.
The hard week: forming the stairwell. The ceiling comes down on the landing, there is a hole in the floor above, and dust travels. It is worth screening the landing and planning to be elsewhere during the day if you can.
The gradual part: once the stairs are in, trades are coming through the house daily. Manageable but constant.
Water and heating: if the tank is being removed and the system changed, expect a day or two without hot water, and plan around it.
Our usual advice: plan to be out during the stairwell week if that is possible, and accept that the rest is noise rather than genuine disruption.
What causes delay
- Approvals started late. Party wall notices in particular — on a terrace or semi a dormer almost always engages the Act, and notice periods run to two months.
- Structural surprises. What is above an existing ceiling is not fully knowable until it is opened: undersized timbers, previous alterations, decay at the wall plate.
- Weather, narrowly. It affects the roof-open phase and little else, because once weathertight the work carries on regardless.
- Staircase manufacture, which is usually made to measure and has a lead time.
- Heating system changes, if a separate trade is involved and is not booked in advance.
- Client decisions on bathroom layout and finishes, which tie to first fix.
What conversions cost
These are the loft figures published across this site:
| Job | Typical Coventry guide price | Notes |
|---|---|---|
| Velux / rooflight conversion | £25,000–£35,000 | Simplest type |
| Dormer conversion | £35,000–£50,000 | Adds head height & space |
| Hip-to-gable | £45,000–£65,000 | End-of-terrace / semi |
| Average loft conversion | ~£35,371 | Type & extras dependent |
A longer programme is not automatically dearer, but a stalled one is — standing scaffold on a loft conversion is a real cost, and remobilising trades after a delay rarely happens the following week.
We give you the on-site sequence and the approval stages, with the party wall timetable shown rather than assumed.
Frequently asked questions
How long does a dormer loft conversion take?
Typically six to ten weeks on site, longer on a trussed roof where steels and a new structural floor go in before any truss is cut. Add design, structural calculations, planning if needed and party wall notices beforehand — those frequently take as long again as the build.
How long is the roof actually open?
Days rather than weeks. The section being altered is opened, the structure built, and it is made weathertight again quickly, with the opening sheeted throughout and the work planned around the forecast. It is a shorter and more controlled phase than most people expect.
Can I live in the house during a loft conversion?
Most clients do, and it is usually easier than an extension because the early work is reached from outside via scaffold. The difficult period is the week the stairwell is cut through the existing ceiling — dust, noise and a hole in the landing. Being elsewhere during that week helps if you can manage it.
Will I lose hot water during the work?
If the cold water tank is being removed and the system converted, expect a day or two without hot water. It is worth asking at quote stage whether the system is changing, because it affects the whole house and it is the kind of thing better planned than discovered.
What delays loft conversions most often?
Party wall notices started too late — a dormer on a terrace or semi almost always engages the Act and periods run to two months. Then structural surprises above the existing ceiling, staircase lead times, and client decisions on the bathroom layout. Weather affects only the roof-open phase.
Is a rooflight conversion much quicker?
Yes, typically four to six weeks against six to ten for a dormer, because the roof shape is unchanged and there is no dormer structure to build. The constraint is that it adds no head height, so it only works where there is already enough.
The sequence, not just the duration
We set out the approval stages, the party wall timetable and the on-site sequence, including which week is the disruptive one. Free survey.