Wrong size cavity in footings!!

S

SillyMonkey

Guest
Checked the footings after the brickie had finished. He left a 100mm cavity in between the two rows of 4" blocks instead of 120mm which is on the plans.

I'm planning on using 80mm rigid insulation and 40mm cavity.

Any suggestions as to what to do since if I want a 120mm cavity all the way up the blocks won't be aligned with the footings.

I have a few thoughts (bar screaming at the brickie) but would like to hear your suggestions.

BTW when I asked him about it he said 100mm was the standard. I said I wasn't building a standard house and it was clearly on the plans. Was greeted with silence.
 
If it's in the plans he'll have to knock them down and do it again, and he knows it. Simple as that.

Reducing the thickness of your insulation because the cavity is too small will increase your annual heating bill for as long as you live in the house.

Plus, if you back down now, who knows what bull you'll have to put up with down the line.

Well done for spotting the problem.
 
I'm in the middle of my own self build at moment and have also put in 80mm rigid insulation into cavities, but the cavities are only 100mm. It still provides enough of a gap for air to circulate, so if you were building with a cavity at 120mm just to increase the gap between insulation and outer wall I'd question whether it's really neccessary. 20mm will still allow air to circulate freely and if dampness is going to bridge it will do it over 40mm just as easily as 20mm, so in my opionion there's no great advantage, unless you have other reasons for wanting it deeper?
 
Your builder was contracted to build what is detailed in your plans surely?? He didn't do it, he made a mistake, and so must rectify it in my view. As already mentioned, if you let him away with this massive mistake, what else is he going to try to get away with, that he's been doing on "standard" houses for years!?
 
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