Garage Extension

[Sloucher]

I have a single skin, brick built garage sharing a common concrete block wall with the next-door neighbour's similar garage. The pair of garages are constructed on a shared concrete raft base and are "stand-alone".

I'm about to extend my garage by 1 metre in width and two metres in length. I intend to build the new walls in block on strip foundations and my question is this:

What's the best way of tying in the old raft base to the new base, which will be concrete infill between the existing raft and the new walls? Should I make it the same thickness as the existing raft edge?

Would I need to reinforce the L shaped new base and, bearing in mind the only load on it will be a workbench or two and maybe half the weight of the car, what sort of mix should it be and whats the chances of cracking appearing between it and the old raft do you think?

Thanks

 

[noseall]

Steel dowels drilled into the existing slab would help prevent cracking.

New slab 100mm thick on 1200g polythene on well compacted hard core.

No need for steel fabric in the new slab unless there are drains criss-crossing the site or other poor ground conditions.

Differential movement between the two slabs will be difficult to avoid so don't be too alarmed if you do get a slight cracking it will be normal.

 

[Sloucher]

Thanks for that Noseall

I assume mild steel rod would be ok, or do I need twisted bar?
Would 0.25 inch diameter rod, inserted into the existing slab by, say, 4 inches be be sufficient do you think? (I don't currently have any longer drill!!!)

Cheers

 

[noseall]

Thanks for that Noseall

I assume mild steel rod would be ok, or do I need twisted bar?
Would 0.25 inch diameter rod, inserted into the existing slab by, say, 4 inches be be sufficient do you think? (I don't currently have any longer drill!!!)

Yes.

It may only be a token gesture though as the forces acting on the whole slab may still be enough to form a small crack.

Fairly normal though.

 

[Sloucher]

Thanks again Noseall. I have a feeling that this build is going to raise more questions in the future!!