Loft conversion drawings & plans, fixed price.

Permitted development & planning

Planning permission for loft conversions.

Most loft conversions don't need a full planning application — they fall under permitted development. In England, a roof enlargement can add up to 40 cubic metres to a terraced house, or 50 cubic metres to a semi-detached or detached house, and Wales allows the same volumes. A few points catch people out:

• The allowance is cumulative — it includes any previous roof enlargements, not just the one you're planning now.
• Nothing can extend beyond the plane of the existing roof slope on the principal elevation fronting a highway, so a front dormer usually needs full planning permission.
• Permitted development rights don't apply to flats or maisonettes.
• They're also removed on designated land such as conservation areas, national parks and areas of outstanding natural beauty.

For the full rules, and what to do when your project falls outside them, see our loft conversion planning permission page. When your loft does need a full application, we prepare the planning permission drawings your council needs and submit them for you.

Building regulations

Building regulations: more involved than extensions.

Every loft conversion needs building regulations approval, and lofts trigger fire-safety rules that extensions don't. In England, once your new floor sits more than 4.5 metres above ground level, Approved Document B expects a protected stairway — an enclosed escape route from the loft down to an outside door, which usually means fire doors on the rooms opening onto the stair. Below that height, an escape window can be acceptable instead. Our building regulations drawings set out how your conversion meets each requirement, so Building Control can sign it off without surprises on site.

Structural calculations

Will I need a structural engineer?

Almost certainly. A loft conversion puts new loads on your house — new floor joists, and usually steel beams to carry the dormer and the cut roof — and Building Control will want calculations to prove it all works. Calculations are included in our Standard and Premium packages, so for most loft projects there's no separate engineer to find. If you only need calculations on their own, we can quote for that too. Not sure where you stand? Read our guide: do I need a structural engineer?

Do you need an architect?

Do I need a loft conversion architect?

What a loft conversion actually needs is architect-designed drawings, because that's what the approvals hang on: planning drawings for the council (or for permitted development), building regulations drawings for Building Control, and structural calculations for the new floor and steels. That's exactly what Arkiplan provides — for a fixed price, from £1,698 or £94 a month.

So if you're searching for a loft conversion architect, the real question is whether you want a full architect's service — concept design, site visits, project management — or the drawings and approvals your conversion has to have. For most dormer, hip-to-gable, mansard and L-shaped lofts, it's the drawings, and we've produced them for more than 2,000 loft and extension projects since 2008, with a 94% planning approval rate.