Beam and block flat roof construction for artificial grass terrace

[frusc]

I'm having a "shed" built in the garden which will have a beam and block roof. The garden is a lot lower then the house so I've got permission to raise to ground floor level. The shed would sit below this level, with artificial grass on top (rest of garden is to be decked to same level).

I'm a little unsure what the best route for finishing the roof would be, before putting the 25mm shockpad underlay and grass on top. Would DPC/screed isolation layer plus 75mm of screed be sufficient. Or is there a better alternative considering it will be walked on.

Thanks

 

[freddiemercurystwin]

Something like RIW Flexiseal Pro would be suitable http://www.riw.co.uk/products/flexiseal-pro

http://www.riw.co.uk/uploads/downloads/TD-FXP-104A.pdf

http://www.riw.co.uk/products/liquid-applied-systems/flexiseal-pro/data-sheet

 

[vinn]

You still need to build your roof to falls. ie it slopes to drainage.

 

[frusc]

You still need to build your roof to falls. ie it slopes to drainage.

I've attached a Garden plan showing the design. The Grass area is where the roof is and shed underneath. The planters at the back are to be built on the roof aswell.

Planning for a fall of 1:60. The roof is to be 7.2m x 3.55m and the fall is to the shorter side, so hopefully it won't be too noticeable. The plan is to meet the decking at the bottom at the same level. The decking to the left will be laid with the same fall. The only visual cue highlighting the fall will then be the fence/wall to the left and right.

The only way I'd found to level off the grass was to lay a GRP grating on top of the roof, level it with battens, then lay the grass and underlay on top. Most people have advised its not worth the added cost/effort as the fall won't be that noticeable.

 

[frusc]

Something like RIW Flexiseal Pro would be suitable http://www.riw.co.uk/products/flexiseal-pro

http://www.riw.co.uk/uploads/downloads/TD-FXP-104A.pdf

http://www.riw.co.uk/products/liquid-applied-systems/flexiseal-pro/data-sheet

Thanks for the pointer, I'll do some research on FlexiSeal pro. I've got 7.2mx3.55m to cover, so hoping I won't get a shock when I google for the price

Should I still lay the DPM + Screed then Flexiseal on top?

The other complication I have is part of the roof will have planters built on top (along entire rear, 3 blocks high, 800mm width). Should I lay DPM under these aswell? I plan to line the planters with DPM, then 200mm pea gravel and drainage pipes to run off excess water to the side, then Geotex membrane and finally soil. I don't want them to get saturated if it rains heavily as that would add significant weight to the roof and also may blow the render.

Would the following be a sound approach:

1) Screed rear 800mm and build planters and add DPM/drainage as described above.
2) Lay DPM on remaining roof and bed into planters wall 50mm up (so it can't be seen once grass/underlay have been laid and the rest can be rendered).
3) Screed remaining roof.
4) Apply Flexiseal.
5) Lay grass and underlay.

Also would it be best to create the fall on the beam and block roof (raising rear footing appropriately), or in the screed layer?

Thanks again for the advice/pointers. Consulted a few contractors and getting contradicting advice.