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?

[EricL]

Hello @dave_022 

Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your low-level deck project.

If you were to dig a pit into the ground for the deck to fit in, you would have to make sure that the drainage for that area is flawless and is capable of taking on a typhoon deluge. Should the drainage fail water will pool in that area and could possibly cause damage to your property. However, before you begin, I suggest checking your local council's rules and regulations in regards to building a low-level deck under an existing deck. What are the space and height restrictions in this type of build.

On the condition that the rules for building a low-level deck does not have restrictions on height between decks, I propose building above ground using standard timber post footings. 

Let me call on our experienced members @Nailbag, @AlanM52 and @Dave-1 for their recommendations.

If you need further assistance, please let us know.    

Eric

[dave_022]

Thank you for your reply. As far as I am aware there are no restrictions for space an height on decks under other decks. I am in Townsville and the local council regulations stipulate planning permits for all decks as it is a cyclone area, this focuses on adequate anchor support.

As mentioned, the current ground to joist for the existing deck is 2100mm, which is minimum height for non-living rooms; technically this is not a room.... but if I add a deck at say 200mm above ground then this space will reduce to 1900mm which would make it very tight for taller people.

[Dave-1]

Good Morning @dave_022 

I am hedging away from installing a raised deck. Majorlly because of the height you will end up with. Going to all that effort to clock your head or clip your arms as they wave about tends me to think of some other type of surface.

I dont like the idea of digging the surface down by much, more so because of the concrete foundations of the piers you have then drainage.

Living in Townsville you will have periods of intense rain that will dump a lot of water. Mmmmm

As much as you may not want to, maybe paving becomes an option. Your yard looks like it slopes towards the back fence so you can have some slope to it to help with pooling. Instead of the stock standard paving you could go with the larger sandstone type pavers/tiles which would match well with your garden and pool. Tuscan Path 600 x 600 x 20mm Sand Porcelain Paver Tho the picture shown dosnt do the tile justice.

If you paved it you could keep your 2100mm distance, I would really try not to decrease that.

Dave

[MitchellMc]

I'd tend to agree with @Dave-1 that paving might be a better option, considering the challenges @dave_022. However, if you can install adequate drainage within the lowered area and have the ability to send that water elsewhere, I don't think digging down would be out of the question. 

You would lower the area, then dig a trench around the area down another 200mm. Place your agline within it and backfill the trench with gravel. The agline can then be run out of the area to a stormwater pipe or an area to runoff.

Mitchell

[Nailbag]

Hi @dave_022 

Looking at the photos there appears to be the concrete foots already starting to be exposed around the top deck posts. Though probably not likely, but digging down could potentially compromise their integrity.

So, with that in mind I too also agree with @dave_022 and @MitchellMc and consider paving instead. This means only having to level the ground of the high-points, laying a min 50mm sand base down then 40mm pavers.

Nailbag

[dave_022]

I have passed the idea of pavers up to the boss and she didn't seem opposed to the idea.

Given the great advice on here, I think I will go with that option. The other advantage is that under the matting is a broken concrete path as well so I may be able to remove some of that to tidy the who area up with pavers as well.

I will post some photos as I go along

[EricL]

Hi @dave_022 

Please keep us updated with your progress, we look forward to the start of your paving project.

Eric