How Much Do Garage Conversion Drawings Cost in Hayes?

Do I need planning permission to convert my garage in Hayes?

Usually not. There are three cases.

Inside only. Works that affect only the interior and do not materially change the outside are not development at all (Town and Country Planning Act 1990, s55(2)(a)). Keeping the garage door and fitting out behind it falls here.

Door replaced with a wall and window. That is an external alteration. On a house with its permitted development rights intact it falls within Class A, as long as the materials look similar to the house (GPDO 2015, Schedule 2 Part 1). No application is needed, though a certificate of lawfulness is useful when you sell.

Rights removed. Some houses were approved with a condition that the garage stays available for parking, or with permitted development rights removed. Then you need planning permission. We read the planning history for the address on Hillingdon's register before we quote.

How does Hillingdon judge the lost parking space?

When an application is needed, this is the test. Policy DMHD 1 of Hillingdon's Local Plan Part 2 says alterations and extensions must keep adequate off-street parking, as set out in its Appendix C parking standards (Local Plan Part 2). The table gives 2 spaces for a dwelling with its own plot. The council's validation checklist also asks every householder application for vehicle parking and access details.

So the drawing that wins a contested Hayes conversion is often the block plan, not the floor plan. It has to show that the driveway still takes the cars the house needs. Many interwar semis in Hayes have a side garage reached down a driveway that holds one car in front of it; some have a front garden already paved. We measure the drive at the survey and show each space at its full size on the plan. Where the drive cannot take two, we say so before you apply, because a lost argument costs the council fee again.

An illustrative example, not a real job: a 1930s semi off Station Road with a side garage, built under a 1960s approval that kept the garage for parking. The drive in front of the garage is 5.5 metres long and the front garden is lawned. With the garage gone, the drive holds one car. The application then needs either a second space shown in the front garden, with its surfacing and access drawn, or a short statement on street parking nearby that explains why one space is enough. Without one of those, the officer has nothing to weigh against the 2-space standard.

The same house without the old condition would need no application at all for the conversion, which is why the planning history check comes before anything else.

If you are thinking of paving the front garden to make room, that brings its own rules on surfacing and dropped kerbs. We flag them; we do not decide them for the highways team.

What about the Hayes Village conservation area and the character areas?

Hayes Village is a conservation area, first designated in 1970. Central Avenue, and East and West Walk, are areas of special local character, and Barnhill Estate in Yeading is another (Hillingdon Council). In all of them, Policy DMHD 1 asks that alterations follow the original house in window pattern, detailing and materials. The plan's design appendix adds that front extensions, including those linked to garages, are not normally accepted.

For a conversion that means the new window and the brickwork under it are drawn to match the house, not just to fill the hole. In the conservation area, an application also needs a heritage statement, which is from £565 and not part of our garage fee.

What does building control need to see?

Every conversion needs building regulations approval, by a building notice or by full plans (Building Regulations 2010, reg. 12). A garage was never built as a room, so the drawings deal with:

• The floor. Usually a step below the house. It is raised, insulated and given a damp-proof membrane.
• The walls. Single-skin side walls are insulated to current thermal standards; our Part L guide gives the figures.
• The infill. The wall under the new window needs a foundation, and building control may ask to see what is there.
• Fire and escape. A room off the hall needs a safe way out, and an integral garage under a bedroom has fire separation to keep or replace.
• Light and air. Window size and ventilation, drawn and specified.

What will the whole conversion cost in drawings and fees?

• Our drawings: from £525 drawings + £150 survey (£675 total).
• Planning, only where a condition or Article 4 direction requires it: £548 to Hillingdon.
• Or, for proof the work is lawful: a certificate at £274 in council fees.
• Building control: the charge set by Hillingdon or a registered building control approver.

If an application is needed, Hillingdon decided 637 of 678 householder applications within eight weeks in the year to 30 June 2026, prior approvals excluded (MHCLG live table PS2).

For more, see our garage conversion planning guide, the garage conversions service and the Hillingdon page. We have also written about garage conversions in Edgware, and if you would rather build out than in, two-storey extensions in Uxbridge.

Frequently asked questions

How do I know if my garage has a parking condition? Search your address on Hillingdon's planning register and read the conditions on the original approval, or any later extension. We do this before quoting.

My drive only fits one car. Will Hillingdon refuse? Not automatically. The standard is 2 spaces, and the council may vary it where there is no harm to street parking. We set out the case in the application, but we tell you first if it is weak.

Can I keep part of the garage as storage? Yes. A front store behind a smaller door is common. The drawings show the dividing wall and any fire rating it needs.

Do I need a structural engineer? Usually only if a wall or beam is removed. Infilling the door opening rarely needs calculations; we tell you if yours does.

Does the converted room need its own heating and windows? It needs enough window area for light and ventilation, drawn on the plans. Heating is your choice, but the room is insulated to current standards either way, so a radiator off the existing system is usually enough.