How to build a low-level deck over concrete?

[Lockmc]

Hi! 

Only discovered this community the other day - what a great resource! 

I will be building a deck under my pergola/undercover area and it will sit on top of the concrete. There is probably 120mm between the concrete and the entry to the house so I was going to only put joists on the concrete.

I have a few questions... 

- what is the best way to attach the joists to the concrete? I know you can buy those tuff blocks but the cost of those will add up. Do I just use an L bracket and some dynabolts? 

- how far off the ground do I need to pack it? 

- do I still flaah the joists even if it's undercover?

- the concrete will be on a slight slant. Do I just use bigger packers on the spots that are falling down? 

Many thanks in advance 

[Lockmc]

Thanks Mitchell.

I think I confused you with my question about being close to the sill.

I don't see any issue in putting the joist close to that sill - but where it runs off to the end, the concrete has been taken out (see my image below where the arrow ends).

So what I was saying - is it ok if the joist is moved to the right by 100mm or so, so that the far end of the joist (near the pool fence) will be supported on concrete?

Or is the best to get some concrete put into that section that was taken out?

[MitchellMc]

Oh, ok, @Lockmc. You're going to just move the issue then, aren't you? Currently, the decking would be overhanging at the end where there is no concrete, but if you move the joist back, the decking will be overhanging the whole way along. Regardless, the same information applies, as I stated earlier. A double joist will need to be used. I've created the rendering for you below to illustrate. Does that look like it would work?

Mitchell

[Lockmc]

Perfect! That is what I am asking, and that looks like it will solve it. Thankyou for all the help

[MitchellMc]

All good @Lockmc! Happy to assist!

Mitchell

[Lockmc]

Hi @MitchellMc.

Another few question if you don't mind. 

The triple joist that will run length ways (the opposite way to the joists) that the pool fence will sit on... This will be at the lowest point. I was going to attach the 3 of them together with some batten screws. Using those KleverKlip adjustable hangers, I don't see any way that I can use them for that triple joist. Any thoughts on how the triple joist can be positioned at the right height? Perhaps just use some timber that comes high enough and use L brackets and bolt to the slab?

And one last one. The board that will run along the stacker door sill... This will be running along the brick sill (but about 20mm higher).

Hoe do I attach that board as the joists won't be running over the brick sill? Picture below might help explain what I mean. 

Or do I have to run the joist over the brick but notch it out so part of the joist runs over the brick sill? 

[EricL]

Hello @Lockmc 

I'm sorry, but can you please explain further when you mentioned the triple joist? At this particular point of your planning stage, I suggest drawing up a decking frame plan so that you can address these type of assembly issues. The direction of your frame will dictate the direction of your deking panels. By finding out your panel direction you can then sort out the installation issue with the KlevaKlip 88mm Nylon ModWood Decking Concealed Fixing Clip.

I also suggest thinking about increasing the height of the decking frame so that it lines up with the panel that you'll be installing on the angled brick. Since there is no timber to anchor onto, I suggest cutting a timber wedge to go underneath the decking panel and you can anchor it onto the brick with masonry fixings. The tricky part is to line up the panel with your actual decking and have the correct gap at the same time.

Once you've drawn up your plan, I suggest sharing it with community. You can then post questions about the framework and other installation concerns you might have.

If you have any other questions we can help with, please let us know.

Eric

[Lockmc]

Hi Eric. 

I've drawn the attached.. Hopefully it makes some sense. 

The triple joists were requested by the pool fence installers to hold the pool glass and are at the lowest point of the deck (top of the below diagram). 

My question is that because I am using the joist hangers, they work fine for a single joist but having 3 batten screwed to each other...those hangers won't work with 3 joists bolter next to each other. So I am wondering what other option I have for raising the triple joist to the right height. 

 

[EricL]

Hi @Lockmc 

Thank you very much for posting your deck framing plan. In regards to the triple joist that will be sandwiched together, I suggest using a nut and bolt assembly to bind them together. I also recommend putting them in a staggard pattern so that the hold on the timber will be spread out. 

As for the footing, I recommend using Builders Edge 70 - 170mm Bigfoot Xl Pedestal Feet. However, if there is not enough space for the pedestal foot, I recommend using 100 x 100mm Post H4 Treated Pine Wet CCA 1.8m dug into the soil to provide proper footing. 

If you have any other questions we can help with, please let us know.

Eric