Design and build contract or appoint my own architect first?

29 Jun 2011
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United Kingdom

We are about to embark on our project of a side return, rear extension and loft conversion in London.

We have had several builders come visit, some offer a full design and build while others need plans before they can provide a firm quote.

Which will work out cheaper - do we appoint a design and build contractor or do we get our own architect, wait for plans and then tender the project?

We have had several architects quotes but they are at least £4k for plans and building regs! But we do want to use someone with PI in case something goes wrong.

At least with a design and build they we will be covered by the builders PI regardless of which architect they use.

Any opinions?
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From my experience, I advise try to find a locally-based architect or building designer, they should have a 'feel' for the buildings in the area. I would not recommend a design and build package, best to keep them seperate.

Also, draw-up an outline of your ideas first, then invite the local planning officer round, to check whether they will approve it in any event; your designer may do this for you, but save cash if you do it yourself. Will you need your designer to supervise/inspect works on site, since the building inspector will only look at what they have to - worth considering.

I do not know what designers charge in London, but planning application is around £150, and building regs. based on floor area I believe - check online.

Best to update the heating/plumbing if necessary at the same time, also any extra electrics - may need new consumer unit for additional circuits, and may need upgrade to mains earthing if - electricians usually insisit on doing this. Plan carefully and Good luck!
You don't just let a design and build contractor loose with nothing to go on. You must provide a design brief. In the commercial world this is known as employers requirements and is basically a full specification of what you want to achieve, materials, standards etc. To be safe this document needs to be very comprehensive so you will need help to put it together and obviously that's going to cost.

I've done both types of contract and for your type of works I reckon an architect/surveyor and then appoint is the best way to go. I agree you should choose a designer with PII. Also ask your designer to advise on appointing the contractor and especially to make sure the correct insurances are in place.
Thanks guys. Problem is kost architects seem to quote £3k - £4k minimum for planning permission + building regs. Is this reasonable?

Standard sortnof extension and loft conversion u see in most London properties and very commonmso not sure if should be forking out this much?
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Unless you're expecting something a bit grand designs you can happily use a technician rather than an architect, choose a one man band and the cost may be a bit less. £3K isn't that bad tbh. I'd be about £1800 if I was doing it as a private job + all local authority fees and structural engineers fees.

If I were doing this as a private job I'd be allowing roughly the following: say best part of a day for survey and discussing brief with client inc travelling etc, say another 4 days to draw up existing and produce proposed plans for the three elements of work, mess around with client refining bits and bobs, submit to planning. All assuming there's nothing controversial and no pre-planning advice is required or it needs a design and access statement etc. After planning, arrange quotes for, appoint and liaise with engineer for loft and any other elements requiring an engineer, say 5-7 days to regs drawings for the three elements, submit to Building control and get approval. That's a good 85 hours give or take assuming all goes well.

Consider someone doing this as their only source of income needs to pay tax, rent offices/printers and everything else that comes with running a business and its easy to see where £3-4K comes from.
in order of cost (general)

architect / contractor

design/build contractor

architect / subcontractors


the lower the cost generally the more risk you take of shoddy work, delays and problems

its up to you how much organising/managing you are prepared to do yourself
and the amount of risk you are prepared to take
it comes down to you get what you pay for, and at the most expensive end what you get for the extra money is a more managed hassle free service and better warrantys, if you went for subcontractors you would get just as good a job as long as you select the subbys well and manage the job well but not as good a warranty
Thanks guys!

But why is architect / contractor more expensive then design build?

I thought design build would be more expensive since they need to be including lots of contingencies as there are not concrete plans yet?

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