Expansion joints in brickwork

[repleb]

Hi

If some one can advise please it would be much appreciated.

We are building a garage/workshop 12m by 6.4m....

We are just below roof level and noticed a couple of cracks in the blockwork
in both a 12m run and 6m run.We have no expansion joints as wasnt specified in drawings,dont think my brickie has ever put in a expansion joint so wasnt aware.

I think we are going to either cut out a 10mm gap where the cracking is(preferred option) to put in expansion joint or cover with a pier.

My concern now is shall we also look to put in a expansion joint in the brickwork.It is a 12m run without any breaks or corners etc in it.

Thanking you in advance for any ideas

 

[^woody^]

Are these shrinkage cracks in aerated blocks due to the mortar being too strong?

You should not need an expansion joint in a wall of that size and for that use

 

[tony1851]

Deja vu again

 

[repleb]

Well the mix used was 1:5 apparently......but in reality I can't be quite sure

 

[tony1851]

aac blocks shrink like mad - the recommendation is movement joints every 6m.
This was raised in a recent thread where some contributors who shall remain nameless seemed to be of the opinion that you can build concrete block walls as long as you want and not bother about movement joints.

If it's single storey and not too high, it should be a cosmetic- rather than structural problem.

 

[^woody^]

You don't tend to see many movement joints in big houses ... with walls 8/10/12m long

 

[repleb]

Thks For input Chaps

I'm guessing after looking at previous logs that in line with nhbc guidelines 6.1 (g) no expansion gaps are needed for the brickwork

 

[tony1851]

Although brickwork expands slightly after construction, on 12m you would probably be OK without an expansion joint, assuming it's a plain wall with no short returns.
As for the blockwork, that shrinks as you have found. If its a vertical crack going through the blocks themselves, just cover it with a pier attached with croc. clips.

@ Woody; houses tend to have windows and doors in external walls and these help to form weak points where slight cracking can occur without being particularly noticeable.
As for the internal blockwork - what cracks are hidden by the plasterboard lining?

 

[^woody^]

Well the mix used was 1:5 apparently......but in reality I can't be quite sure

It should be no stronger than 1:6, more like 1:8 IIRC