What our drawing fee covers
Our fee, from £2,535 inc survey, covers the measured survey of the existing house and the drawings that go to the council: existing and proposed plans, a section through the new floor, elevations of any lightwell or front-area change, and the location and block plans. We are chartered architectural technologists, so the set is drawn to the standard a validation officer looks for.
What it does not cover is the ground. A basement is a structural and a water problem before it is a design one, and the drawings follow the engineer's answers on slab depth, underpinning and waterproofing rather than guessing at them.
The other bills: engineer, neighbours, council
Structural calculations are the next cost. Ours start at £435, and the engineer's design for underpinning a Georgian or Victorian terrace sits behind them.
Digging triggers the Party Wall etc. Act. An adjacent excavation notice is needed where you dig within three metres of a neighbour's building and deeper than their foundations, or within six metres where the dig cuts a 45 degree line from the bottom of their foundations. The notice goes out at least one month before work starts, and our notices start at £55 per neighbour.
The council's fee is the third bill. A basement under a single house normally goes in with a householder application, which is £548 from 1 April 2026.
Why the borough matters more than the square metres
There is no single London rule. The London Plan leaves the detail to the boroughs: Policy D10 says boroughs should set their own policies on large basements where this is a local issue, and several have. Some want a basement impact assessment on the ground and groundwater; some limit how far a basement extends under the garden.
That is why we read the borough's policy before we quote. A two-storey cellar under a Camden terrace and a single-storey one under a Chelsea villa are not the same application, even at the same floor area.
What building control will check below ground
Below the planning drawings sits the technical set. A basement bedroom or living room needs a way out: an escape window or external door, or a protected stair to a final exit. Ground movement must not damage the building, so the structure is designed to Approved Document A.
Water is the part owners underestimate. Where the water table can rise within a quarter of a metre of the bottom floor, Approved Document C asks for drainage by gravity or other effective means, and a basement with a bathroom needs a drainage plan that deals with sewer surcharge. Our building regulations drawings cover these items.
Getting a fixed quote
Send the address and we start with a free check of the borough's basement policy, the street and any listing or conservation area. You then get a fixed fee in writing. See our basement conversion drawings page for what is on each sheet.
The figures, with sources
£548
What the council charges for a householder application covering a basement under one house.
Source: Ribble Valley Borough Council, national fee table from 1 April 2026, checked 17 Oct 2026
3 m / 6 m
Distances within which excavating next to a neighbour's building can need an adjacent excavation notice, at least one month before work starts.
Source: Party Wall etc. Act 1996, section 6, checked 15 Oct 2026
14 days
Time an adjoining owner has to consent to the notice in writing before a dispute is deemed to exist.
Source: Party Wall etc. Act 1996, explanatory booklet (GOV.UK), checked 15 Oct 2026
D10
London Plan policy asking boroughs to set their own rules for large basements where this is a local issue.
Source: London Plan 2021, Policy D10, checked 15 Oct 2026
0.25 m
Water-table height under the bottom floor at which Approved Document C asks for drainage by gravity or other effective means.
Source: Approved Document C, paragraph 3.2, checked 15 Oct 2026
Para 2.16
Basement storeys with habitable rooms need an escape window or external door, or a protected stair to a final exit.
Source: Approved Document B Volume 1, checked 15 Oct 2026
100 m²
Floor area of new build under which no Community Infrastructure Levy is due, unless a dwelling is created.
Source: Community Infrastructure Levy Regulations 2010, regulation 42, checked 15 Oct 2026
Questions
Do I need planning permission for a basement?
Usually yes. Digging a new basement or adding a lightwell is development, and most London boroughs have their own policy on it. We check the borough before we quote.
Is the engineer included in your fee?
No. Structural calculations are a separate service, from £435, and the engineer's design for the structure is separate again. We coordinate our drawings with it.
Will the neighbours have to agree?
They do not have to agree to the planning application, but if you dig close to their wall the Party Wall etc. Act applies. Notice has to be served, and if they do not consent a surveyor settles terms.
Does the price change for a larger cellar?
The starting price covers a typical period house. A deeper dig, a second storey or a lightwell on the front elevation takes more drawing time; the fixed fee we send after the free check says exactly what it covers.
The fee for basement (cellar conversion)
Basement (cellar conversion)
from £2,535
inc survey (£2,335 if you supply measured drawings). No VAT to add.
Get a fixed quote from £2,535What you get
- A survey of the whole house, measured by us and included
- Plans, a section through the new floor and elevations
- Location and block plans drawn to validation scales
- Drawings coordinated with your engineer's design
- Free redraws until the application is approved
