Building a raised patio

windym_2

I am after some help regarding a new raised patio.

Story so far - the 10m x 3.8m deck has been removed in part that was adjacent to the barn.  The bit at the end is much newer and will stay in place for the moment, the plan is to build the patio at the same height (300mm - just under to comply) to be the same height as the original deck and level with the deck at the end. 

We are at the very early stages as we haven't yet decided on what slab we want to use and are researching locally.

But to get started we want some advice on how to actually build the base of the patio.

The barn is a few hundred years old and like most barns has no foundation but has been tanked internally.  Therefore we don't have a DPC to worry about per se.

Our original thought was to get concrete in and pour a slap to suit using shuttering ply as the framework.  We could either build this directly up to the barn - perhaps having rendered the outside up to 250mm say and then apply a waterproofing of some description.  Then lay the slabs on top.

Or do we build a retaining wall as the framework for the patio and infill that.  If we do this should we build it away from the barn and make a drain (there is a soakaway further along which we could tap into). 

Or is there a better solution?

Fairly competent at DIY but haven't tackled a patio before. 

Couple of pics to explain - yes it does look like a bomb site but we aren't in any rush as we have two other entrances around the other side. 




This is what was there. The bit at the end that goes in the 90degree opposite direction is staying for the moment.





Posts will be going this weekend hopefully. 






Thanks for any pointers/ideas. 

stuart45

I'd build retaining walls myself, but not use a concrete slab. A well compacted MOT base allows moisture to drain down. Lay the slabs on a weakish mix to allow the same. Point up in a stronger mix. Nowadays I take the slabs up to the brick on edge of the retaining wall, and not over the top of it.

FreeBear

stuart45 said:

I'd build retaining walls myself, but not use a concrete slab. A well compacted MOT base allows moisture to drain down. Lay the slabs on a weakish mix to allow the same. Point up in a stronger mix. Nowadays I take the slabs up to the brick on edge of the retaining wall, and not over the top of it.

Same here. Leave a gap between the barn & retaining wall and fill it with gravel. Build up the base for the patio with MOT1 or crushed rubble. Do it in layers, compacting each one as you go. Bed the slabs down on a 10:1 sand/cement mix 25mm or so thick.

Don't go pouring a ruddy great slab of concrete - If you or a subsequent owner needs to dig it out, solid concrete will need heavy duty equipment to break it up. At least with MOT1, it can (just about) be dug out by hand.

stuart45

The other issue with concrete is that any water getting through the joints in the slabs can sit on top of the concrete, freeze and lift the slabs.
The only time I would use a reinforced slab is on really poor ground.
Polished concrete patios can be exceptionally attractive,  but it's finding someone good enough in this country.

windym_2

Thanks all.  Seems a wall is the way to go.