Low-level deck over slab with very low clearance

[StewyBurritos]

Hey everyone, 

I have been doing a bunch of research on building a low-level deck on an existing alfresco slab and extending out into the backyard. The issue I face is that if I want to be flush with the internal flooring, I only have 75mm at the highest and 85mm at the lowest to work with. Some help from the community would be greatly appreciated to push me in the right direction.  

Important details about the project
- Total deck 6730mm x 3660mm

- Alfresco slab 3350mm x 3660mm

- Min clearance from slab to flush internal flooring 75mm

- Max clearance from slab to flush internal flooring 85mm 

- Decking material will be Ekodeck (137mm x 23mm 5.4m)

I've looked into pedestal systems such as the Builders Edge 25-40mm Minifoot Pedestal Feet but with joists on top would be too high. 
Here are some photos of the space and it would be great to understand the different ways to achieve this deck.

 

[MitchellMc]

Welcome to the Bunnings Workshop community @StewyBurritos. It's brilliant to have you join us, and many thanks for your question about creating a low-level deck.

Due to the height limitations, there are not too many ways to achieve a deck in this space. 75mm height to build a deck within is really not enough room for any conventional frame type. You'll be looking at a limited lifespan to the deck and premature failure. The only way you could come close to building some type of frame to lay your decking on would be to place 90 x 45 outdoor framing timber on its 90mm face. It loses a lot of its structural rigidity by doing that but would then allow 23mm for your decking and a 7mm gap under the frame for drainage. A 7mm gap for drainage and airflow is really minimal and will lead to early decay of the structure.

There are plenty of low-level deck projects contributed by our members that you might like to read through. Yours would be at the extreme end of the scale. You'll also find this guide on How to build a low-level deck useful.

If you have any questions please let me know.

Mitchell

[Jason]

Hi @StewyBurritos,

Welcome to the Bunnings Workshop community. 

I wondered whether you might have considered tiling over the slab instead? Perhaps a timber-look tile?

Mitch would be able to provide suitable product suggestions. 

Jason

[MitchellMc]

@Jason has an excellent point @StewyBurritos. Timber-look tiles would be a fantastic solution in this space. Check out these porcelain Brunswick floor tiles from Johnson tiles, perfect for alfresco areas. We can Special Order them into a store for you.

Here's a helpful guide on all you need to know about timber-look tiles.

Please let me know if you have any questions.

Mitchell

[StewyBurritos]

Looks like I didn't get the measurements right. 

I have a bigger clearance than I thought but is still very tight. 

- Min clearance from slab to flush internal flooring 100mm

- Max clearance from slab to flush internal flooring 110mm 

[MitchellMc]

Correct, it's still very tight @StewyBurritos, but it brings you into the realm of placing 90 x 45mm joists on their 90mm face. 45mm timber + 23mm decking + 25mm minifoot = 93mm. You'll have 7mm for drainage under the timber joists.

Mitchell

[StewyBurritos]

@MitchellMc what about 70 x 45 fixed with angle brackets to the slab? 

70+23=93. Raise it up with the brackets to be flush.

[EricL]

Hello @StewyBurritos

Now that you have more space, the 70x45 along with the Elodeck is a possible combination. However, being a smaller piece of timber, I suggest putting extra angle brackets along the run to prevent it from twisting and bowing. I recommend reading this discussion - Low-level composite deck by @oninpena. I also suggest reading - How to build a low-level deck by @Adam_W. You might pick up some techniques that will help you assemble your decking frame.

Here is a link for ideas and inspiration: Inspiring low-level deck builds  

If you need further assistance, please let us know.

Eric

[khusnil_deo]

@StewyBurritos  
i have been following your posts and I am in a similar situation with a very low clearance. I was suggested to do 90by45 with the wide face up but it loses its structural integrity as Jason, Eric and Mitch has mentioned.  I am now going to look into timber look tiles.

Would love to know how you solved your subfloor heights and what did you use?

Thank you