How to build a low-level deck?

yeahboo

Hello everyone,

I'm trying to build a deck in our alfresco. At this point, it's still on the planning stage. I've seen a few posts here and there on this forum and would very much appreciate some further inputs to more experienced people than me.

My background: I work in the IT industry and "hardware" isn't really my thing lol. Anyway, I've built a few benches, and tables (nothing fancy) but not really built anything as big as an outdoor deck.

Project Alfresco: We have a small alfresco that my wife insists should have a deck. I agree, and I want to build it myself. Here's some bit of a challenge. The brick height is low, and also, "not even" from the side near the wall (corner of the doorway), it's around 130mm slopes down to 125mm the other side. Also, what would look good:(1) building the deck only on the slab of the alfresco, or (2) including the one outside as well?

Should I build a deck to included the ones outside the Alfresco slab?height is 130mm from the left sloping down to 125mm to the right

Need suggestions on best way to build it, should I use this? https://www.bunnings.com.au/tuffblock-300-x-300-x-90mm-instant-foundation-system-deck-support_p24103... shour I do something else? Open to any suggestions at this point since this is my first build.

thank you.

EricL

Hello @yeahboo

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

Let's do some quick math, if you have a space of 130mm less a 90x45 joist that would leave you with 40mm less the thickness of a standard timber decking panel 19mm and you will end up with a gap of 21mm. It is therefore possible to use standard framing timber and Merbau decking panels.

I suggest having a quick look at these guides - How to build a low-level deck by @Adam_W and How to build a deck by @MitchellMc. These guides will give you an idea of what to take into consideration when planning your decking frame. In regards to the uneven slope of your concrete base, I suggest using Builders Edge Pedestal Foot. In combination with your choice of angle brackets you'll be able to adjust the footing to compensate for the fall.

I suggest having a look at this featured project - Low-level composite deck over concrete and soil by @oninpena. It's an excellent example of using pedestal feet in combination with angle brackets.

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

Eric

yeahboo

Hello @EricL ,

Thank you for your response and the very useful links. In your experience, do you reckon I should plan on creating a deck over the alfresco slab only or extend it a bit on the outside?

Thanks.

EricL

Hi @yeahboo

I love large open decks; It feels like I can go to the very edge of my property without getting my feet dirty. Personally yes, the bigger the better, there will be no need to bunch in your outdoor furniture or your BBQ as there is enough space to spread it out on the deck. But I will leave that decision up to you.

Eric

yeahboo

Hello @EricL ,

I found this site: https://www.blocklayer.com/deckcalculator#tblBoards to help me calculate the timber I will need (minus the stumps since I will be using the tuff block most likely)... with this tool, what's normally the gap between joists? is the default 450mm ok, or should I use 500mm?

Now, I think I'm convinced that I'll make the deck bigger.. so I measured the area and it's 4750mm x 4250mm. However, it wasn't a perfect rectangle.. How will you normally go about handling that in the planning?

Thanks.

MitchellMc

Hi @yeahboo,

450mm centres on your joist are the typical spacing.

Whether the deck is 4000mm x 4000mm or 4750mm x 4250mm the planning is much the same. Your joists are spaced every 450mm across the span. If you have any particular questions, I'd be happy to determine the answer for you.

Mitchell

yeahboo

Hello @MitchellMc ,

Thanks for that clarification. I have a ton of questions actually. I'm very new to this.

Given that the area I want to build a deck in isn't exactly a rectangle, is it correct for me to assume that the frame I build should be the smallest possible rectangle I can fit in the area (while considering the ? like if the measurements are 4750x4250 but it decreases from 4250 to 4220 on the other corner of the width.
Regarding the timber that I will need, for the frame, I'm OK witht he link that was given by @EricL to use that 90x45mm for the joists. However, I'm not sure with the other timber that I will need. For the fascia board, is it different than the decking board? how about the picture frame when placing the boards, is it the same board? I assume it is, but I could be wrong so I might as well ask. haha.
Tools - Aside from the measuring tools and the cutting tools, what other tools will I need to complete this?
- Measuring Tape
- Spirit Level
- (for the angles, what tool is that?)
- Circular Saw (do I need a Mitre saw? or will this be enough?)
- I only have this actually: https://www.bunnings.com.au/ryobi-18v-one-home-essentials-kit_p0327892 I will need to buy everything else for this project and hopefully, can re-use for future DIY
- I have a workbench that can be a saw horse, so I'll need another one I guess
- Chalk
- For sure I missed something, please do tell me what other tool I missed.

I think that's it for now. LOL. I will for sure have more questions after this being a newbie.

Thank you!

MitchellMc

Hi @yeahboo,

How is the area you want to build in not entirely rectangle? It's always best to build a deck with square corners, but it is possible to create a deck of any shape. You just need to put more thought into how you'll design the frame. As you said, creating the largest rectangle to fit into that space is a good start, and then you can modify the frame to suit the inconsistency. If you can provide the exact dimensions of the deck, I'll draw some illustrations for you.

It's all the same decking boards. However you might choose 90mm boards for the deck, but then the fascia requires a larger 140mm board. Or, you might use 140mm boards for your deck and only need a 90mm board for the fascia. Check out this guide on How to build a deck. I trust you'll find my explanation helpful.

You really don't need a great deal to consult a deck. Check out the lists in the above article. They are the bare minimum, and everything else is a luxury. Your list encompasses just about everything. You'll also need decking spacers. A circular saw is fine. You'll see most of the cutting is done with the boards on the deck to keep things consistent so a mitre saw isn't actually so helpful with this project. It would be nice for cutting the framing timbers, but a circular saw does that just fine on your saw horses.

Mitchell

yeahboo

Hello @MitchellMc ,

Oh that would be great if you could help on how it will visually look. The area isn't exactly rectangle by only a few cm on the width side. Length is 4750 (both corners), and the width is 4250 on one side, and 4220 on the other. I actually measured twice to verify if I just made a mistake, but yeah, it's really 4220mm on the othear side. the one near the house wall.

Thanks!

MitchellMc

Hi @yeahboo,

I've included an image of your frame below.

Sorry, I presumed you were saying that there was a significant out-of-square issue going on. You're talking about all of the 30mm difference. Can you please let me know more about where this occurs? It would be best to make the deck a consistent rectangle and avoid this very small difference if possible.

Mitchell