DIY Doctor UK DIY Forums

Not sure if right forum but here goes,

Single storey extension is pulling away from the main house, i suspect it hasn't been tied into the main house at all. Is it sufficient to strap it some how to the main building or do i need to underpin? the extension is single skin so would have to be demolishedif i wished to extend above it (which i do not). Builder has told me strapping it would be enough. What type of straps do i need (they have to be right angled as cannot use conventional wall ties now) and how often doi repeat the process ie everyother course.

thanks Darren

I would guess that the single skin extension is only on a slab foundation and so is moving / subsiding. Straps would only cause the brickwork to crack further along.

I do not think that you have much option but to consider underpinning. Is it worth consulting your insurance?

hth, good luck

xavi

thanks for reply, just few more details

extentsion built 98
house purchased by me 2000
total movement less than 10mm in 12 yrs
no movement to base of structure
assume floor due to air bricks
suspect strip foundation or poss slab if floor joist laid onto slab.
what i intended to do was strap the extension at every other course using Expamet Heavy Duty Zinc 1200 x 27.5 x 5mm Bent 150mm plates.
150mm onto the main structure of house and 1200 to the extension wall at every other course both sides of the extension internally. Fixings being hilti bolt type expanding bolts in High performance injectable cementitious grout. The 1200mm would stretch two thirds of the way down the extension either side.
there is no evidence on the outside of ground movement.
My feeling is that this movement maybe the result of settlement of the new part of the building as there was a 16ft front to rear drop in the back garden which has since been raised and levelled so an additional 30 plus tons of earth are now support the front of the extension prevent slippage.

Could also be differntial movement as the extension foundation moves whilst the house foundation is settled?