raised deck posts onto slabs

[lynnlmwelsh]

is it ok to lay slabs which will support raised decking onto soil ? the soil would be 3/4 inches deep with solid concrete underneath. there would be 8 4x4 inch posts supported on the bolt down type of post feet each one would be sitting on one concrete paving slab (measuring 3 ftx 2 ft @2" thick) or should i use a solid base for them if so can i use the ready mix postcrete instead of traditional concrete ????

 

[WabbitPoo]

3/4 inches of soil on concrete? That's odd. Why not just scrape it out of the way?

 

[lynnlmwelsh]

on reflection its probably about 6 inch of soil but anyway i think the concrete may be to cover the sewerage pipes the soil pipe from the toilet goes into the ground and there is a drain vent where the slabs are. the concrete itself underneath is very rough and slopes the same as the slabs its an ex council house built about 50 years ago I guess the finesse wasnt too important.

any ideas how to proceed ?? should i just lift the slabs and level the ground out then relay a few for the posts to sit on

 

[WabbitPoo]

simplest way of putting it is:

make sure that whatever you sink your posts into or onto, that it doesnt move.

Without seeing it its a bit hard to know the best route for you, but most pros will sink at least some of the posts onto a narrow but fairly deep flared hole (wider at the base) and then concrete them in.

Oh, and dont bother with post anchors.

 

[lynnlmwelsh]

ok thanks !! so hows this for an idea ( if its stupid tell me but be gentle lol) where the posts would be on the bit which is concrete under the slabs which are on the worst slope i could dig down to the concrete ( 6 inch depth) and use post crete to make a sort of pillar which would sit on top of the concrete. the pillar as i say could only be 6 inch deep and god only knows how wide ( help with this please) and the posts could bear onto this.

is that sensible or should i just use the old paving slabs to save any hastles and i suppose they would also spread the load better since they are 3 ft x 2 ft.

im confused i thought it would be dig some holes set some posts hey presto done

 

[WabbitPoo]

well if the concrete slope is, well, sloping, then the posts dont stand much chance of staying put.

If you have big old 3x2 concrete slabs then these should be ok of the ground i sound.

I would recommend u find SOMEWHERE to anchor the deck, not from the point of view of sheer weight, but to stop any lateral creep flexion.

 

[lynnlmwelsh]

right slabs it is then thanks. the 4 posts which will be furthest away from my house will be concreted/postcreted in, this area is grass at the moment and i have dug a couple of test holes to see what the ground is like. its full of half bricks and lumps of sandstone but with the use of a pinch bar and some elbow grease i can get down roughly 2 feet. I assume having these 4 concreted in and the others standing on slabs will suffice. I suppose if the worst comes to the worst i can add some cross braces under the deck like thermo talks about but i think it should be fine ( but what do i know lol)

 

[WabbitPoo]

worst case scenario in these things is: you build it and 6 months later it feel springy, in which case add some more/better supports.

Simples.

IOW, dont over-engineer it.

 

[lynnlmwelsh]

cheers mate