concrete slab base

30 Jun 2003
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United Kingdom
How would I go about laying a concrete slab base for a garage floor. The garage is attached to the house. Do I :-

1.Dig out and lay the foundations and build the 3 sides up to ground level.

2.As the ground has already been prepared with compacted hardcore, can I just dig down the 150mm then lay the DPM (1200 visqueen).

3. Pour the concrete in up to ground level.
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pumabhoy said:
The garage is attached to the house.
Form what I understand is,the garage is already up and you want to concrete the base? The dpm must be bedded on soft sand.
Sorry, I should have explained it better. I posted a few weeks ago about building a garage as all the quotes I've had have been very expensive so I was looking into doing it myself.
The garage itself is still at the planning stage (I have plans and building warrant) until I've done enough research into what needs done and if I would be able to do it. Most is straight forward except the floor and roof. What I really need to know is if I should do the floor right at the beginning or the end.

Do I dig and lay the foundations, build the bricks/blocks on foundations up to ground level and sort out the concrete base.


Do I build the garage in full and then sort out the concrete base at the end.
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pumabhoy said:
Do I dig and lay the foundations,
Yes, do this first then find your dpc on your property and go down to minimum 3 brickwork courses plus another 10mm from the dpc level and that should be your foundation height level.It's very important that the footing is level by putting in square timber pegs on the side of the footing for levelling the height.Also this is a very useful tool,the tape measure which will help you to get the height brickwork and how many bricks of difference type etc but not cheap,approx £13.(Fisco Brick Mate)


build the bricks/blocks on foundations up to ground level
The next step is to use common bricks or engineer bricks which is good for below dpc level and build up your courses to the same level of your property dpc level,then hardcore or rejects finish off with pea shingles to fills the little holes etc plus soft sand on top to protect the dp membrane.The dpm go on top of sand up to the new dpc level and over the wall with the dpc on top of the dpm then pour concrete on top of the dpm to your finish floor level.Once this is done then you're ready for blocks laying.
ps:don't forget to slide the new dpc onto the top of the dpc of the property,you can carefully cut out the groove with a angle grinder.

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