DIY Doctor

Building a single skin block garage - Required foundations?

Postby mctaggart » Thu Jan 05, 2012 2:47 pm


I am looking to start building my own double garage in the spring. I am just gathering information so i can plan to build the garage my self. Looked into the council and i dont need planning for the size on my plot but i do need building regs as its over 30m2. its (42m2)

I wanted to build a large double garage with room for a workshop, will be single skinned blockwork, with a pitched roof.

I wanted to know exactly what specs are required to do to dig out my footings and get my concrete in.

Could someone explain in detail whats required to lay my slab, the ground its going on is firm with a high degree of rock in it, so very stable, a digger is planned to get up.

The garage is going to be 5.5m x 8.5m single storey.

The questions i have are:

What exactly do i need to spec up the footings, i.e how deep, how wide, do i put anything in them before concrete goes in? etc

Once the footings are dug, how deep shall i dig out for the slab, also again whats required, i assume i stick in wire mesh then pour concrete over and skim.

This is my first time doing the footings and slab so want to get it right, hope you can help so i can just read through whats needed to be done and then carry out the work.


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Simply Build It

Postby stoneyboy » Thu Jan 05, 2012 6:02 pm

The depth and width of your foundations will depend on sub-soil conditions also if you live in scotland with deep frost penetration you will have to go deeper to eliminate frost damage. Dig a trial hole and get the BI to agree what is needed.
For the slab you need to remove soil to a stable base and allow for 150 - 200mm depth of concrete with the mesh in the middle. You could incorporate a DPM at this stage. For a garage you should be able to achieve a reasonable surface finish without a skim coat.
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Postby xavi99 » Fri Jan 20, 2012 9:02 pm

Foundations, traditional strip would be min 1m deep excavation, 450 mm min width, 750 mm depth of concrete. Does depend on ground conditions.

Oversite - 150 mm well compacted hardcore, (25 mm sand blinding, 1200 guage dpm if you want one), 100 mm concrete with one layer A142 reinforcing mesh.

Alternative would be to get an engineer to design a simple raft foundation, less ground to excavate and dispose of.


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