Deck over sloping concrete base.... Options?

2 Nov 2009
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United Kingdom
I want to deck over the area described below;

Open up the back door and the first part of the garden is concrete slab – the area I want to deck is approx. 12ft x 28ft. There is a step down from the back door onto the slab.

The slab slopes UP towards the next part of the garden – a 24ft x 28ft artificial turf section (not touching this for this project). In other words, the slab slopes down towards the house.

I want to use decking to bridge the space between the back door and the artificial grass. In other words, deck over the top of the existing 12ft x 28ft concrete area. The concrete is in decent conditions so had it not been sloping, I guess it would have been a simpler project but as I said there is quite a slope on it – around 10 inches in height between the start of the artificial lawn section (high point) and the base of the rear wall of the house (low point).

Almost by coincidence, the height difference is identical to the height of the back door step so I am envisaging opening the back door and immediately stepping onto the deck (no up or down step needed) and this being one level decked area all the way to the artificial grass area.

When I lay the joists the furthest away end will be at ground level whilst the end at house will need to be 10 inches off the ground to account for the slope. Has anyone any experience in such a build? How best to fix joist to a solid concrete floor with one end 10 inches higher than the other? Can I attach the ‘high’ end to the house itself or will this cause problems with trapping rainwater etc?

Any help appreciated.
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does rainwater run down the concrete slab to the house wall? -it sounds like there should be a surface drain adjacent to the house
How far from the house to the artificial grass?
Is it 12ft, or 28ft?
How thick is the concrete slab?
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Yes, it slopes towards the house but at the same time it slopes away down to the drain so water doesnt collect at the base of the house wall.

12ft to the artificial grass.

Concrete is too thick to remove to dig in posts.

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