Movement in new cavity wall

redders1 · 2 Jun 2009

I am in the process of building a rear single storey extension. I am up to roof plate on each side wall and up to the same height with just the gable end to build on the rear wall. The rear wall is approx 6.1m in length with openings for a rear door and an opening for a window. The external measurements from each corner are approx 700mm wall, 1800 window, 1800 wall, 850 door, 950 wall.
The problem that I have noticed is that the 1800mm wall section in the middle of this run seems to have some movement in it. i.e. the wall appears to move/vibrate if you press/shake against it. It is difficult to describe but the other walls do no seem to do this.
Is this normal and will it be more sound when the roof is on and tied to the gable end.
It is standard block construction with 100mm cavity. Externally it will be rendered. The window is approx 900mm from floor but will be full height from there as the room is double vaulted. It will mimic the angle of the roof so will have no blockwork above it
Any advice/comments would be great thanks.

noseall · 2 Jun 2009

Single slabs of wall will have movement yes.

So much so, that it important to 'back-in' (build the inner leaf of blockwork) rather than leave it to the elements, i.e. wind, over night.

Once the lintels are in place or wall plates fitted then the walls become stable.

Shytalkz · 2 Jun 2009

There is no load on the wall at the moment, so it's at its most vulnerable from lateral loads. Once you've got the roof weight on, it won't be doing what you are describing.

noseall · 2 Jun 2009

Gotcha Shy.

Shytalkz · 2 Jun 2009

You did, by a nanosecond

redders1 · 2 Jun 2009

Thanks Noseall/Shytalkz,
You have eased my worries somewhat. I was mostly concerned as the internal skin of the gable end will be taking the weight of a steel at ridge height which will in turn carry the weight of the roof. (this has been specified as there will be no roof joists to tie the rafters as it is double vaulted)
Do you think the instability of this wall will pose problems or as it all comes together will that wall stabilise?
Many thanks again

noseall · 2 Jun 2009

Stability or indeed restraint issues, regarding a joistless or vaulted roof, should have been addressed in the design. No?

redders1 · 2 Jun 2009

Yes, your absolutely right Noseall and this was the reason for the high level steel to prevent the roof from "spreading". I was just surprised to see the movement in the wall I earlier described which will eventually take this steel.

noseall · 2 Jun 2009

I guess it is a bit un-nerving the first time you se a wall wobble.

Believe me, it is normal. Don't go shaking it too much though.

redders1 · 2 Jun 2009

Thanks Noseall, much relief this end!!

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Movement in new cavity wall

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