How much does a loft conversion cost: what the job involves and who is registered to do it, and how much does loft conversion cost once building control, the staircase and the structural work are in the figure

How how much a loft conversion costs works

1. Settle whether it is permitted development. A great many loft conversion are permitted development, which means no planning application, but the limits on depth, height, materials and how much of the plot is already built on are specific and a designer should read them against your own house before anybody prices anything.
2. Get drawings and a structural design. Existing and proposed drawings, then a structural engineer's calculations for whatever is being opened up or carried. On a loft conversion this is a small share of the total and it is what turns an idea into something three builders can price identically.
3. Serve the party wall notices in time. Work on or near a shared wall, or excavation within three or six metres of a neighbour's foundations, engages the Party Wall etc. Act and the notice periods are set in months rather than weeks. Serving late is the commonest reason a start date slips.
4. Price it against a specification, not a sketch. Ask each builder to price the same written specification, with provisional sums shown as provisional sums. Two quotes that differ by a third almost always differ in what is included: the kitchen, the flooring, the decoration and the drainage diversion are the usual absentees.
5. Agree stages, retention and building control. A staged payment schedule against completed work, a small retention until sign-off, and a clear statement of who is notifying building control. The completion certificate is what a future buyer's solicitor will ask for.

Insurance and paperwork

Common questions

Why do quotes for the same loft vary so much?

Usually because they are not quoting the same job. One may include the staircase, the ensuite and the decoration and another may not; one may assume the existing roof structure can be opened up cheaply and another may have costed a proper steel design.

Is a modular loft conversion or a prefab loft conversion cheaper?

It can compress the time on site, and the groundwork of drawings, structure, approvals and party wall notices is the same. Craning a module in also has access requirements that a terraced street may not allow.

What is usually excluded from a quote for loft conversion?

Decoration, floor coverings, fitted wardrobes, the ensuite specification above a basic allowance, and sometimes the staircase joinery. Ask for exclusions in writing and price them before you compare totals.

Registered contractors by region

• Registered roofers in the East Midlands postcode area
• Registered roofers in the East of England postcode area
• Registered roofers in the London postcode area
• Registered roofers in the North East postcode area
• Registered roofers in the North West postcode area
• Registered roofers in the Scotland postcode area
• Registered roofers in the South East postcode area
• Registered roofers in the South West postcode area
• Registered roofers in the Wales postcode area
• Registered roofers in the West Midlands postcode area
• Registered roofers in the Yorkshire and The Humber postcode area