Low level decking over concrete

[Fadi]

Hi everyone,

Firstly, sincere apologies for posting another low-level decking post. I was unable to find some details I was looking for. It's my first ever decking project and pretty much new to tools and products, please never mind if I don't use the correct wordings.

Here we go,

I am trying to build low-cost decking over an existing concrete slab. The height between the slab and the finish floor levels (FFL) is about 120mm. My first question is;

Is it a good idea to level the deck with FFL? Any issues/complications this will have in the future?

I am thinking of using "70 x 35mm MGP10"  as for underneath timber with Hot dip galv. angle bracket for concrete fixings with about 10mm clearance between the slab and the frame mainly for water drain and air/flow.

Is 10mm clearance good enough?

What sort of bolts shall I use for angle bracket fixing to concrete?

Also, see a detailed timber layout for comments and suggestions on spacing and etc.

Community manager's note: Check out How to build a low-level deck for expert advice.

I will be finishing it off with SpecRite 90 x 19mm 2.25m FJ Merbau.

A quick mock-up of how it will look like if everything goes smoothly;

Current situation;

Thanks in advance

[MitchellMc]

Hi @rahil_xyz,

It will depend on what orientation you decking boards are laid. Are they running parallel to this doorway or perpendicular to it? If they are running parallel to it then you might want to start your first board there and offset it and have it hanging 10 mm off the side of the ledger board/bearer to close the gap. If they are running perpendicular you could do the same and have the boards slightly overhanging and butted up closer to the door sill.

Bear in mind that you need some type of gap here to allow airflow and prevent moisture buildup inducing timber decay. 

I'd encourage you to start your own discussion about your deck that way we can delve further into your questions in more detail.

Please let me know if you needed further information or had any questions.

Mitchell

[th-DIYER]

Hey @MitchellMc and @Fadi when securing the angle bracket to timber what are you using? A nut and bolt or screws...? I’m building a small 1000 x800 timber platform/step on a concrete slab.
Thanks in advance. 

[MitchellMc]

Hi @th-DIYER,

You could use Zenith 14G x 50mm Galvanised Bugle Head Batten Timber Screws or for an extended lifespan Zenith 14 - 10 x 50mm Stainless Steel Bugle Head Batten Timber Screws. You can also bolt the joists to the bracket, but this could be a time-consuming process depending on how many you are doing. If you were to go the bolt route, I'd highly recommend you purchase an attachment for your drill that will allow you to fit sockets to it. You can then drive all the nuts onto the bolts with a drill.

Please let me know if you have any questions.

Mitchell

[Fatsquare]

Hi, can I post my questions here because I am also going to diy low level decking on the concrete slab. But the clearance height is 60mm only.. any idea to which H3 treated pine is situable for this job. 70mm*45mm? Just want to confirm that the nails are using to  connect the joists ( I am using 70mm*45mm H3 treated pine, 45mm is the height,  not 70mm, because it is really low.), Right? I don't have nail gun( mine is electric nail gun which 35mm maximum length which is not suitable for this job) , so do you have any idea which size of nail is perfect for this job? And  do I make the whole frame first( it may be easy for me to nail the joist by hammer), then secure the frame to the slab?

[EricL]

Hi @Fatsquare

Thank you for sharing your question about your low-level deck project. I understand you want to use nails for your joists, but I suggest using Zenith 14G x 50mm Galvanised Bugle Head Batten Timber Screws instead. The screws will provide a greater amount of holding power due to the threads of the bolt. An ordinary nail when stressed will pull out much faster.

The assembly process you mentioned is one way to create your decking frame. However, I am concerned with your allotted space of 60mm. The 70 x 45, even when turned to the 45mm side and joined to the 19mm decking panel will give you an overall measurement of 64mm. It will be 4mm past the 60mm space which now becomes a tripping hazard.

I recommend re-assessing the space you have and perhaps considering either breaking up the surface of the concrete slab so that you will have more space or tiling it with a timber look profile on it.

If you need further assistance, please let us know.

Eric

[Fatsquare]

Thanks for information, Eric.

It maybe lots of job to break up the surface of concrete slab. I am now breaking up the surface of slate tile in my living room. It is a job I wll never want to do it again.  I am exhausted , it is more than 20 years slate tile, uneven and tough to remove:)

It is OK for my decking. I have one easy option. The decking is 63mm(45mm+19mm) high.  I put 10mm wide tile on the 60mm high area between the deck and the door. The tile  will level the 60mm area to the same height as the door step. Tile color may be carefully considered.