Laying concrete over previous concrete / foundations?

[julianf]

Last week we took down my pre-fab concrete section garage.
It was sat on small foundation walls (2 blocks depth) with a soil floor.


Im wanting to put new foundations in, and a concrete slab for the floor, and put the structure back up. Nothing wrong with the old foundation walls at all, but im moving the job by about a foot, so nothing will line up any more.

There was also a path down the side of the garage - about 2" of concrete.


Say i want to put in a 6" base - can i leave the 2" path in place, and put 4" above it? Same with the old foundation walls? Does this create some sort of fixed pivot where cracking will occur?

All existing stuff has been in place since the early 70s and shows no movement, so soil is pretty stable here (a lot of rock mixed in with the soil - no clay)

Thank you.

 

[li150ss]

put reinforcing mesh in concrete slab

 

[gaz1]

Last week we took down my pre-fab concrete section garage.
It was sat on small foundation walls (2 blocks depth) with a soil floor.

Say i want to put in a 6" base - can i leave the 2" path in place, and put 4" above it? Same with the old foundation walls? Does this create some sort of fixed pivot where cracking will occur

All existing stuff has been in place since the early 70s and shows no movement, so soil is pretty stable here (a lot of rock mixed in with the soil - no clay)

Thank you.

where the path is make sure if its supporting the base to take up at this point the rest of it leave at 4"

it its the door way you can drop it to 4" leaving the original path alone

remember only at supporting the wall points to take up

 

[julianf]

I'm going to do the foundations first, as the job is too involved for me to do the slab in one go. So the path / original foundations will come up where ever they go, but the internal floor will only go in once the structure is up again.

I don't 100% understand your comments but does that make sense to you?

 

[CornishPete]

If the path is only 2" thick and the existing foundations are just 2 blocks then it shouldn't be too difficult to take up. Might as well do a proper job.

 

[gaz1]

remove the path if it where the garage panel is going to go make sure its a proper foundation the 8" held up due to it being a thick base in the first place

by being 8" thick your intending to use 4 + 2 " flag not a good source best to remove and replace with a thick bed

only if its where the garage door is where you dont need that thickness of base where you can get away with a 4" base

my shed is based upon your concrete blocks only

as ive dug around the shape of garage a spade deep and poured in concrete to make a nice thick base a spades depth 8-9" deep concrete base

 

[chris pruteanu]

Do it properly, do it once! Dig the old fundation up and make it dewper and wider to take the weight of the new fundation also use mesh to reinforce the slab. Use a decent polipropilene sheet under the slab to stop moisture in and dont forget to damp course the walls- engineering bricks are good at that + use dampproofing membrane above the ground where you raise it on the block work. What sort of finish youre going for render or pebble dash? In easrern europe people clad the walls in polistyrene sheets and render on top of mesh- its fine as it gives a straight substrate but rubbish if you want to hung something up! Fortunately uk weather is nothing as the mainland winters so yiu can get away with non cavity walls! Spend well on rafters- make sure they are tanalised timbers to last.... Good luck!