How do you do a 'spec' for an extension if you have no idea what and how 'the rules' work?!

[Erebus]

I was reading a thread about someone who couldn't get builders around without planning permission already granted where people were saying they needed to 'get a spec' to give to a builder but it struck me- how do you get a spec if you don't know what sort of floor, ceiling construction, sort of walling are needed to meet structural and planning rules etc? What if you don't know how wide an area you can span before needing a supporting column? I'm not a structural engineer! That person was doing a small job so didn't want to pay out for an architect. I must say I thought the stuff you submitted to council had to have all of that, like 'house plans' attached but the examples I saw have got DIY line drawings of the proposal, no more detail than that, to get through Planning.

How could you get builders to quote like for like if one says 'You need a floating floor' and the next says 'I'll span that with a couple of bearers' or whatever. I know I could, presumably get an architect but I want to have some idea about what it's all likely to cost before chucking £600 at it.

WWYD?

You'll need an expert. If you don't want to ask an architect you can also ask a Building Surveyor to write a spec for you, although costs may be similar. Really, if you don't have the expertise you need to pay for it or you'll be at the mercy of a builder.

As a rough guide, allow £1000 per square metre for basic new build, rising to £2000+ per square metre if you have expensive taste. That should give you a rough idea of costs, and then you can decide whether to bother going further. If you do, get a spec written so you can compare like for like on builders' estimates.

Erebus, we are knocking down some internal walls and got an architect to draw up plans for the builders and for Building Regulations approval and he got a structural engineer involved to do the structural calculations. The plans and calculations have the technical specification on them and we supplemented them with a written scope of works which said things like "Replace skirting boards throughout ground floor with new skirting boards to be supplied by client" - essentially a long list of extras.

We're currently waiting for our estimates from builders and haven't a clue what to expect. It's all very scary exciting.

We've just done it. We're putting a 2nd extension across the back of the house. It doesn't require planning consent and
First we got a builder to tell us that it was technically feasible and we got a building consultant to draw us up some rough plans and elevations.
Then we found a kitchen designer to design us a kitchen to ensure the space was big enough. Having seen the plans (which were dreadful) we decided we needed to loose the wall between kitchen window and patio doors to give us a large space without a central column.
So we got a structural engineer around to confirm we could knock out a couple of walls and to specify what we needed in terms of rsjs.
Then I wrote to the planners to get them to confirm in writing that it was permitted development.
Then we went back to the building consultant and asked him to help is draw up a specification - which was mostly "insulate roof space to building ref standards). After going out to 4 builders and chasing for responses, 1 replied (the guy who had originally come to see it). His quote was quite arsey because it wasn't a full spec and he'd got all stroppy about phrases like "bricks to match existing" because he didn't know what they were (even though he'd looked at the house a couple of months previously and didn't come back to revisit). So we went out to 3 more builders of whom 2 replied.

One was fab, spent an hour and a half talking through stuff we wanted and came back with a reasonable quote. He's since been back to talk through his quote and is starting in Sept. He wants building regs sorted up front rather than relying on a building notice so building consultant is back doing a detailed spec for him.
That's how we've done it. It's a bit circuitous and we've ended up spending about £1 to 1.5k on upfront stuff but there won't be any long term project management costs so with that less than 10% of build costs, I'm happy.
Whether i'll regret this in October when I'm trying to manage it, the plumber and builder have fallen out and we have no heating, we've been living in a bombsite for 6 weeks, and my mat leave has ended and i'll be back at work I have no idea...

If you don't clearly specify exactly what you want, the various builders will price it according to what they think you want, which may include using a very basic spec which will be cheap (enabling them to bid low for the contract) but meaning you will later have to add on the extra stuff you actually want (for which they will charge as much as they can get away with)"

Sooner or later somebody is going to have to say what you want. It might as well be you. Defining it before getting a price is a million times better than doing it after you are committed. If you have to pay a professional to help you, so be it.

*This is why Government contracts for everything from Aircraft Carriers to IT systems are notorious for time and budget overruns. The specification was not properly defined in advance of placing the contract. This leads to unbearable stress and grief, and the contractor very often loots the customer. The customer has no-one to blame but himself. Sorry.

You don't need fancy drawings. You need information. That is more important than format. So hand drawings and the back of a fag packet are perfectly ok if they cover all the stuff you need.

If you don't have the confidence/time/ability to learn everything that is required to draw up plans and a spec then you need to find someone to do it for you.

Without the right info it will be slow, painful and you might as well give the builders your debit card and PIN as no spec is an open invitation to get ripped off and/or end up with a defective building. If you are lucky your extra costs will be the same as the plans fee you want to avoid - but in my experience costs will spiral far higher so it is a false economy. And that's without considering the negative effect on your property value when you come to sell and have a non compliant building....

But crack on and give it a go! You are the one who has to deal with the consequences while all the posters edging you on will not be seen for dust!

Good luck!!!!!

Like me, many architects will come to your house and give you an opinion of your proposal and informal advice as to the possibilities, alternatives, practicalities, legalities and so on.

I give potential clients up to one hour free. If I am in a particularly good mood and am offered wine good coffee and cake, I may stay a bit longer and even throw in a free sketch or two if the proposal interests me.

The downside is sometimes my advice may be, "don't bother, move instead" or something similar.

The only proviso is locality - obviously the client must be reasonably close!

BTW this wasn't meant as an advert!

Just a suggestion you have a look in your area for architects.