Vertical cracks straight through breeze block

[fangio]

Hello,

I had a garage built 4 months ago and it has suddenly developed vertical cracks, from floor to ceiling in three of the walls. I know they are straight through the breeze block because I had the builder remove some of the rendering across the crack. The crack is less than 1mm but obviously it is early days. The builder was going to charge me 7.4K (6m by 5m) garage but I have held back just over 3k. Is this what remedial action such as underpinning (what else could I do?) is going to cost?

The builder seems to think this is pretty normal, but I cannot believe that. Also a friend said they should have used concrete block and put in expansion gaps. He told me that breeze almost always cracks in these applications.

The foundations are dug to 0.5m The garage is almost three metres high.

Obviously the builder is pretty annoyed I have held back the money and is starting to get very insistent, veiled threats etc, So if anyone could help I would be most most grateful, this whole thing is starting to worry me to the point where I am losing sleep. If anyone could give some advice on what I should do I would be most most grateful.


Thanks,
Fangio.

 

[billm]

if it were me, I'd get another builder to give you his opinion of the build and if the cracks are serious and need rectification and if so how much.

Or alternatively, you could ask the local building inspector from the council to assess it .. although you might have to pay for his visit.

 

[noseall]

i have seen vertical cracks in blockwork that was built upon foundations laid on clay. the summer that year was wet followed by a long dry spell.

sound familiar.

the foundations had two layers of reinforcing mesh within and the concrete was supplied by delivered batch. it made no difference because of the clay.

oddly the outside brickwork was not affected, i guesss because the smaller brick units were more adapted to movement.

 

[BuilderSte]

firstly its not normal, far from it. nosealls comment was right, if the ground beneath the stripfooting has changed state and expanded or shrunk due to weather this could account for it. however if your footings wentdown only 500mm you may not have reached virgin ground and therefore the building has settled as it compresses the earth, causing cracks as it settles to varying degrees at diff points. i cant be sure of this tho as i dont know the ground conditions where you live.

 

[fangio]

Thanks for the replies!

The ground conditions are indeed clay. Can I reasonably have expected the builder to have known that he should have gone down to "virgin" clay? He is telling me that he has built "hundreds of garages and this has never happened" and is expecting me to pay further money should I need to underpin the building. But none of the other garages in the area (less than 10 metres away) have cracks in them.

Should it have been built with concrete blocks and have expansion gaps?
Should I get him to pour concrete beneath the foundation where the cracks have appeared? Is this likely to prevent the cracks from getting worse.

 

[Robert too]

Hello,

Also a friend said they should have used concrete block and put in expansion gaps. He told me that breeze almost always cracks in these applications.



Thanks,
Fangio.

I concur with your friend.

I never spec breeze blocks as an external skin , despite what the catalogues say you can do with them.

 

[NS215]

did BCO inspect the ground conditions before allowing the concrete to be poured

 

[Robert too]

did BCO inspect the ground conditions before allowing the concrete to be poured

If its under 30m2 it probably didnt need Building Regs

 

[Thermo]

got any photos? if its on clay sounds possibly like ground heave as noseall and Builderste have referred to. What were the foundations, simple strip footings? If they were then it makes no difference that they should have gone down to virgin clay. it will still suffer from movement form the presence of water. Would have been better to have built the slab and the foundations as a raft to allow for the movement.

 

[BuilderSte]

in my opinion , on clay, a properly constructed concrete strip footing would be suffficiant. provided the footing is of adequate depth, width and has a good fill of concrete. recently completed a very similar size garage, a little longer but a little narrower. however we are spoilt were i live as we have some of the best ground conditions for building you could wish for.
ps robert, you never spec breeze block externally? thats a relief as they haven't made them for years

 

[Thermo]

unfortunatley it would appear he doesnt have the ideal ground conditions!

 

[fangio]

Once again thank you for the replies.

I was told by my builder, that because it is 30m2 and 70 feet away from the house, building control do not need to get involved.

When the builder was doing the footings I noticed he placed rubble in them...what depth of rubble should you have for a 0.5m strip foundation? Do you fill the foundation with rubble and then pur concrete on top? I am now thinking I should dig down and actually check what the foundation is like where one of the four cracks have appeared.

The more I talk to our builder, the more I wonder why on earth I ever trusted him to a good job...I think I'll enquire here for a bit of advice before ever embarking on anything like this again.

Thanks again,
Fangio.

 

[Robert too]

Once again thank you for the replies.

When the builder was doing the footings I noticed he placed rubble in them...Fangio.

ding ding .....................

theres the problem

 

[fangio]

Thanks Robert. Pardon my ignorance but why is that a problem?

 

[joe-90]

If he used 300 mm rubble and 200 mm concrete - then your foundation is really just 200mm. The rubble will settle with the weight of your blocks - and the foundation will fail. You may have to dig the whole lot up and start again.