How to add drainage for low level deck?

[dave_022]

I am looking to utilise the space under our current deck for another decked area extending to the fence to increase the pool area (moving fencing back which will cut across new deck area)

The issue I have is clearances, the current under deck height is 2100. Therefore the preferable height would be for the deck to finish level with pool slab which is 100mm from ground.

In order to do this I am aware I would need to dig down. I was planning to use joints on tuff block to keep it as low as possible. Although the under-current deck area will be sheltered by the top deck and roof from some rain I am still concerned about pooling under the deck if it effectively sits in a pit. What would you recommend for drainage solutions? or is this overall an unworkable idea?

[dave_022]

Unfortuinately the storm water pipe runs down the side of the pool closest to the house and as the pool slab is 100mm higher than the rest of the area then that is not a direct connection. The other side of the slab runs very close to the fence to another block wall, so no way out there either. Would some kind of sump and pump work?

[MitchellMc]

At the moment, it looks like you’ve essentially created a low point where water collects @dave_022, which is why it’s pooling so badly. A sump and pump could work, but it’s worth considering whether there are simpler ways to manage the drainage first.

For example, what’s to the right-hand side near the shed? If possible, you might be able to dig a short ag line there to divert some water away into another part of the yard. Also, the lowest point appears to be down at the fence. If the aggregate base is levelled correctly, a lot of that pooling should reduce naturally. Once your paving is installed, water won’t penetrate as easily and will mostly run off, especially if you grade the paving slightly towards the backyard.

Given the current water level, I’d recommend building up the aggregate so the top of the base sits at or just above the current water level. Then when you lay your paving, it will sit higher than the water, so even heavy rain shouldn’t cause pooling on top of the pavers.

Essentially, ensure the aggregate is raised enough to give the water somewhere to soak in without sitting on the finished surface. 

Mitchell