Are extension dimensions supposed to be to plan?

Solus · 17 Feb 2017 at 08:55

Seems like a stupid question, but I've now come up against this.

In my drawings by the architect the width of the extension is to be 4.7m, though we're now at dpc level and the outside walls measure 4.6. There is a manhole which the builders are telling me is taking up more room than in the plans under the concrete, fair enough I thought. However, I don't know if this is true and also, should I expect part of the cost to come off?

kaktus · 17 Feb 2017 at 09:30

Talk to your architect and explain the situation so he can clarify if his drawings took into account the substructure of the manhole drain.

If you didn't agree with the builders that the manhole drain needs to be moved or the concrete burrowed out then they're not at fault but they could've warned you that the internal area will be slightly smaller before laying the foundations / brickwork so you could discuss any adjustments to the manhole drain (bear in mind that this is likely to cause you more headache than it's worth as you will have to pay for the drain to be relocated and reinforced and you'll probably need the sewage authority's permission).

Tbh for 10cm I would't bother about it. Granted, with internal walls and insulation if you have any you will lose about another 15-20cm but still plenty of room

FTM · 17 Feb 2017 at 11:39

we made a couple of changes as we went on as the builders spotted some practicalites as they were going

the rear patio doors we made slightly smaller as the reveals either side would have been tiny and looked wierd, and again the bricklayer suggested positioning the windows on the front slightly different to the plan so they then matched the width of the doors to the rear (we got two tall narrow verticals..we didnt want the neighbour opposite to feel we would always be looking into her sitting room)

its also about a brick and half longer than originally drawn, this was down to positioning of the double doors through from the exisitng building so it appears central in both the old and new rooms
there was no problem with the council

Solus · 17 Feb 2017 at 14:51

The insulation is within the cavity, so thats not too bad. Obviously I'll have plasterboard dot and dab to go on so that'll be a bit more off which I knew anyway. I suppose it's just quite bad they haven't mentioned it to me.

Also damaged a coping stone on my front wall I only had built last April, which I will mention.

andicole0 · 17 Feb 2017 at 14:54

Don't get too stroppy with your builders, you are relying on them a lot.
Also when we had a house extension we got the Architect to 'manage' the builders.
Andi.

Solus · 17 Feb 2017 at 16:51

The job they've done so far has been great and they've been more than courteous over things. I am only coming across stroppy here as it's an internet forum, I would always discuss it amicably. I just wanted to get other people's views on it before I even mention it.

The actual extension was priced at £23100 and based on roughly 1090 per metre squared. 0.1m x 4.5 = 0.45 metres squared missing, which multiplied by 1090 = £490.50 should come off the total price.

Am I wrong to be working it out like this? They worked it out per m2 when I signed the contract.

the_r_sole · 17 Feb 2017 at 19:05

Have they priced it exactly on a square meter cost? What kind of detailed drawing and specs do they have?
IMO it's not advisable to start requesting reductions, they've had to move the foundation because of your site, presumably they have set up and dug the trench to discover that they'll have to dig a new foundation? So it's not as simple as just dividing the square meter price by the reduced area...
The only thing is to check with your architect that the size change doesn't have any implications for activity spaces or corridor width etc

Solus · 17 Feb 2017 at 20:37

the_r_sole said:
Have they priced it exactly on a square meter cost? What kind of detailed drawing and specs do they have?
IMO it's not advisable to start requesting reductions, they've had to move the foundation because of your site, presumably they have set up and dug the trench to discover that they'll have to dig a new foundation? So it's not as simple as just dividing the square meter price by the reduced area...
The only thing is to check with your architect that the size change doesn't have any implications for activity spaces or corridor width etc

They dug the trenches and didn't have to dig separately. They measured the required 500mm from the manhole and that's where they dug. It's just ended up smaller than quoted and in the drawings. It's not that any extra work has occurred, it's simply that there is no possibility to make it 4.7m and has to be 4.6m. I am planning some "extras", an outside light, and a patio. Would it be reasonable to expect this extra work at reduced cost?

the_r_sole · 17 Feb 2017 at 21:16

Solus said:
They dug the trenches and didn't have to dig separately. They measured the required 500mm from the manhole and that's where they dug. It's just ended up smaller than quoted and in the drawings. It's not that any extra work has occurred, it's simply that there is no possibility to make it 4.7m and has to be 4.6m. I am planning some "extras", an outside light, and a patio. Would it be reasonable to expect this extra work at reduced cost?

It depends on how they've priced it, you haven't said what their pricing is based on...
If you start off at foundation digging asking for discounts you can guarantee they will see you as a penny pincher and it won't make for a happy atmosphere for the rest of the job. And every extra will be charged at full whack

Lumeycom · 17 Feb 2017 at 23:06

the_r_sole said:
It depends on how they've priced it, you haven't said what their pricing is based on...
If you start off at foundation digging asking for discounts you can guarantee they will see you as a penny pincher and it won't make for a happy atmosphere for the rest of the job. And every extra will be charged at full whack

This.

Dont squabble over a minor amount of cash as it will cost you in the long run. Also have some heart for the builder as its not his fault that there are services in places that was not expected, thats down to the design. If you insist on going after the money then it would be whoever designed it really, not the guy building it as he has done the right thing,.

a1ex2001 · 17 Feb 2017 at 23:45

Don't sweat it building an extension is never straight forward and architects plans often fail to take into account the real world!

Solus · 18 Feb 2017 at 08:25

Thanks all, I will leave it at that and continue the good atmosphere. As you said, it may work against me to penny pinch in the long run.

Thanks all!