Do I fill hollow blocks with mortar or concrete?

15 May 2013
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United Kingdom
Im building a wall for a garage. The blocks are 6inch hollows. Do I fill them with concrete or mortar? I have a feeling its concrete.

Also do I need to do all the filling at once or can it be done in stages?

Thanks for your help
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I'm only a diy but I'd do concrete, it's cheaper because of less cement, less shrinkage, and the holes should be big enough to take the aggravated.
None? Why do you need concrete in them?
The wall is 10m long so I was advised to do 6inch hollows filled if I wanted to avoid building peers. Im guessing if I put rebar in them and drill down into the slab then I can fill them in stages.

Only problem is switching from concrete to mortar with my mixer means the odd few stones get into the mortar mix.
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Wouldnt it have been easier to build one or two piers in brick, rather than fill in 10m of hollow blocks?
It could of been tony if I was any good at brickwork but as im not i'll go with the filling method. Im just a DIYer so try not to get too much out of my depth with these jobs. The slab is pretty thick 6-12inches and has reinforcing mesh and footings trench so it will be able to take the weight.

I have remeasured the wall and it is closer to 8.5metres if that makes any difference.
If your joist height is under 2.4m then I would not bother.

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