Fixed price · £1,650

Single-storey extension, plans, regs and calcs, £1,650 fixed.

The drawing-and-calc pack for a rear, side, or wrap-around single-storey extension. Includes the structural calcs for openings and foundations, drainage layout, and the full building regs pack you need for Building Control.

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+ £199 admin fee. Larger or non-standard projects priced individually.

In the pack

What's included.

Everything you need to submit to Building Control and hand to a builder. No part of the pack is "extra", the price you see is the whole pack.

Site measurement visit + existing measured survey (within our coverage area; 3D Matterport on request)
Existing & proposed floor plans, elevations and sections (CAD)
Structural calculations for new openings, lintels and pad foundations
Foundation design appropriate to the soil and any nearby trees
Drainage layout, new connections, manhole positions, rainwater
Thermal and U-value notes for Building Control
Building regs drawing pack and structural calcs, the full set you need for Building Control (you or your builder lodge it)
Planning application managed and submitted for you when one is required (£199 admin fee)
Build over agreement when required (+£195, paid to Thames Water etc.)
Two rounds of revisions during design

Honesty section

What it doesn't cover.

The things below sit outside the package, either because they're a different profession (Party Wall surveyors, builders) or because not every project needs them. We'll flag what applies to you before you book.

Planning permission application (often permitted development; we advise per project)
Party Wall award fees (paid to surveyors directly)
Building Control submission fee (paid to the council)
On-site construction or project management
Mechanical and electrical drawings (your builder/electrician handles these)
Listed building or conservation area consents (priced separately if needed)

Optional add-ons

Bolt these onto your home extension.

Tick on the quote form or mention them on the designer's call.

3D render

Photoreal view of the proposed scheme. Plus £65 for additional views.

+£165

Expedited turnaround

Drawings drafted in 7 working days instead of 14.

+£450

Common questions

What people usually ask before booking.

Will my extension need planning permission?

Single-storey rear extensions up to a certain size go under permitted development. Side or wrap-around extensions, conservation areas and flats are different. We confirm before you commit, and if you do need a planning application, we'll quote that separately.

What size of extension does the £1,650 cover?

Any single-storey extension up to the standard permitted-development envelope. Larger schemes (two-storey, basement, very wide spans) are priced after the site visit but use the same fixed-price approach.

How long does the pack take to produce?

14 working days from the site visit, or 7 with the £450 expedited add-on.

Do you coordinate with my builder?

We hand the pack over in a format builders are used to seeing, and we answer technical queries from your builder during construction at no extra charge for the first two weeks after handover.

Book an extension, fixed price, no quote-after-a-call.

Drop your postcode in. If we cover it, you get an instant yes and a booking link. If we don't, you get an honest no.

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