Gap opening between extension and existing bungalow wall! General problems, solutions, information and advice on fixing to walls of all kinds

[derekh110953]

Hi there.
We moved into our bungalow in 2007. It's a 1964 build completed just before Building Regulations came in. In 2001 the previous owner erected a largish single story extension along the side of the property, approximately 10M in length and 4M wide. I beleive he carried out a large part of the building work himself from comments he'd made when we 1st veiwed the property.
We decorated the extension just after moving in and repaired what appeared to be minor settlement cracks along the length of the interior wall where it meets the ceiling.
We have noticed that the cracks have returned and opened now by about 3mm at most since decorating. On checking the exterior where the new brickwork joins the bungalow there is a gap of about 6mm at eaves height which narrows to about 3mm at ground level.
I was informed by a builder i employed last year for some other improvements that the new wall would have been tied to the existing brickwork using what is called a wall plate fixed to the bunglow side wall with brackets hung from it and into the new mortar to properly fix the new to the old.
I was worried the gap seems to be getting larger so this afternoon decided to investigate what was hidden behind the joint between the two walls believing the wall plate hadn't been bolted adequately to the side of the bungalow.
Well can't say as I was surprised at what I found as other work carried out by the previous owner I have discovered to below par.
There are a total of 8 fixings over the full height of 3M. 4 are 4in galvanised nails driven into the old mortar beds at lower level. The old mortar is not good and is very sandy and the nails barely hold. Further up there are 4 galvanised L brackets about 1mm thick, again fixed poorly into the old mortar but well mortared into the new beds.
So there is no wall plate and none of the new brick is bonded directly into the old wall.
Now a few of questions:-
Should the Building Inspecter have checked that the new and old were correctly and properly bonded back in 2001, I have the certificates here at home by the way.
I have thought about making the problem good by clearing out the old and new mortar beds and inserting some very heavy duty galvanised pressed steel 210mm wall ties I have to hand at every other mortar course. Would you have an opion about how adequately this would hold the extension to the original buliding.
Any advise or opions would be gratefully recieved

Derek

[stoneyboy]

derekh110953,
If the extension has moved outwards that much I would suspect inadequate foundations. Try digging a hole outside and see how deep the foundations are and what subsoil conditions are like. If you are on clay the foundations should be 1.5+m down.
end

[derekh110953]

Thanks for the input on my problem Stoneyboy.
To be honest the possibility of something being wrong with the extension footings had really worried me.
I've had a chat with a helpful guy at the local Building Control who also pointed out that if there was a gap developing it was more likely to be a footings issue than the walls not being tied together properly, though he agreed the lack of a crocodile plate was not good but more of a issue of poor workmanship.
However whilst on the phone I suddenly realised that the floor that runs through from the old kitchen area into the new kitchen diner extension is finished with ceramic floor tiles covering the area below the crack in the wall ceilling. The tiles are totally intact and I'm assured that these would cracked given even a very small amount of movment at floor level. These tiles have been down now for well over 3yrs to my knowledge so I think I can breathe a lot easier now.
So I'ill now work on the premise that the gap is not actively moving and will repair using the new wall ties and repoint the now exposed joint but will keep a watchful eye on the area in the future.

[stoneyboy]

derekh110953,
Thanks for the feedback.
I would suggest you determine whether movement is still occurring by fitting movement gauges high up on the wall. These don't need to be more than a narrow piece of glass with a score across the middle attached to the two walls with a 2-part adhesive.
You could also try tapping the tiles laid across the join between the kitchen diner and kitchen and see if they sound hollow they could be bridging a movement crack.
end

[derekh110953]

Thanks for the advise StoneyBoy.

Haven't cheeked my email in sometime so sorry about the delay.

Well I decided to make the joint good myself and went ahead and used the heavy duty ties and repointed it all. Did this about 6 weeks ago now and it looks much better now. I'm convinced the bulk of the movement happened some years ago but will be keeping a close eye on things now.

Derek