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How to build a low-level deck?

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_p2410345 shour I do something else? Open to any suggestions at this point since this is my first build.

thank you.

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Comments

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

https://www.workshop.bunnings.com.au/discussion/comment/33872#Comment_33872

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

https://www.workshop.bunnings.com.au/discussion/comment/79282#Comment_79282

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

https://www.workshop.bunnings.com.au/discussion/comment/103997#Comment_103997

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

https://www.workshop.bunnings.com.au/discussion/comment/119096#Comment_119096

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

https://www.workshop.bunnings.com.au/discussion/comment/128091#Comment_128091

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

https://www.workshop.bunnings.com.au/discussion/comment/133938#Comment_133938

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

https://www.workshop.bunnings.com.au/discussion/comment/137591#Comment_137591

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

https://www.workshop.bunnings.com.au/discussion/comment/140096#Comment_140096

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

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/141868#Comment_141868

Hello @MitchellMc ,

The 3cm difference is from the one near the house, and this one near the grass.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/143181#Comment_143181

So, in this case, @yeahboo, I'd just make the deck a perfect rectangle working off the largest width. On the smaller end, the deck will overhang the edge of the concrete 3cm, but that won't be seen underneath it.

Mitchell

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/144131#Comment_144131

Ok that makes sense I guess. and if in the future, I want to add a deck patch leading to that door, the logical thing is to make a straight line from the existing (assuming I finish this lol) one right?

Also, another question I have regarding the frame... I plan to use the pedestal blocks, and I am assuming the edges of the frame near the wall and doorway should be "touching" the wall right? In that case, how should I go about placing support for the frame near the wall/doorway? or is that where the anchors come in? (Which Eric said I should try and do a combination)

Thanks!

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/144840#Comment_144840

That would be correct, @yeahboo.

So, you'll create a frame for the deck structure and then fix the joists within it. You'll screw through the frame into the ends of the joists. The feet can then be placed under the joists instead of under the frame as they are connected. That allows you to set the feet in from the wall and the deck's perimeter.

Unless there is a need to connect the frame to the wall, I would try to avoid that, as it adds another layer of complexity. There's no issue creating a floating deck entirely supported by the pedestal feet.

Mitchell

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/145386#Comment_145386

Hello @MitchellMc ,

I'm about to buy the materials I will need, just another quick question. What's normally the standard space if getting a 90x19mm decking board? Also, what's usually the deciding factor when choosing between 140mm vs 90mm. And if it's a 140mm decking board, what's the standard space between boards? Lastly, if I'm getting 90mm boards, I need to pre-oild before install? and will I be able to get boards of length near that 4220mm (although if I am to use picture frame, should be less right)

Thanks!

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/145807#Comment_145807

Hi @yeahboo,

With either the 90 or 140mm boards you'll want at least a 5mm gap between them. The choice between them comes down to personal preference. Do you like the look of the wider or thinner board?

Neither the 90 or 140mm board must be pre-oiled before installation. Typically, the boards would be laid and then oiled.

In set lengths, you'd need to go with the 5700mm Merbau decking boards to cover your 4220mm in one board.

Mitchell

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/146130#Comment_146130

Hello @MitchellMc or @EricL ,

I have a question regarding the leveling of the whole frame... so for example with the 130mm height of the brick, and 90mm joist, 19mm board, I'm left with around 21mm to explore from the door of the house towards the outside.. now how should I go about leving this? @EricL mentioned I can use a mix of pedestals and brackets but what I can't wrap my head around is..

1. Do I build the frame first, and start putting them in the bracket/pedestal combo? or

2. Do I build the frame as I level each joist?

how do I go about adjusting the parts related to the bracket? like if I use this bracket for example: https://www.bunnings.com.au/dunnings-40-x-80-x-40-x-5mm-m12-galvanised-angle-bracket_p1070088

thanks.

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/146408#Comment_146408

Evening @yeahboo

Man I can feel your excitement and must say I am a little bit envious 🙂 Sounds like it will be a great looking deck.

To answer your question, Id build the frame first and then level the lot, at leats the outside edges. I have not used those pedestals before but think they will work the same way the feet do for kitchen cupbooards (they are infinently adjustable)

Id get it level with the pedestals and then bolt the brackets in, the pedestals will do all the hard work of holding ot level while you drill.

Looking forward to the project pics 🙂

Dave

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/146408#Comment_146408

Hi @yeahboo,

Have a look at this guide: How to build a deck. As @Dave-1 mentioned, I'd build your frame first on the ground, as it will be easiest, and then pop the adjustable feet/brackets under it. I'd cut several 59mm high blocks of timber and use them as temporary chocks under your frame whilst you install the brackets and feet.

Keep us updated!

Mitchell

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/146631#Comment_146631

When I drill with the brackets, how to take into account the "minor" movements from the bolt and holes? For example, the bracket I linked, if I try an M12 bolt, it "wiggles" a bit. Or is that room small enough to ignore? Also, the timber near the wall, I can't use a nut/bolt there right if I want the timber to "touch" the wall?

Having a hard time figuring out which nut/bolt and screw to use tbh haha.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/146814#Comment_146814

How much is the bracket moving around @yeahboo? When you tighten the Dynabolt down, it should grab the bracket and lock it into place.

To use bolts near the wall, I'd drill your holes through the frame and then flip it over and enlarge the hole so the head of the bolt is recessed inside the frame. Flip it back, push against the wall, stick the brackets over the exposed threaded sections and tighten the nuts up.

Please let me know if you have any questions.

Mitchell

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/146961#Comment_146961

Maybe 1mm? Note I'm just trying it from Bunnings. Sample.

is this the right bolt? LOL.

Sorry, obviously, my inexperience is showing and thanks again for taking time to answer my questions

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/147079#Comment_147079

Oh, that's fine, @yeahboo. I thought you meant you'd installed the bracket onto the concrete, and it was moving around after doing the Dynabolt up. That's no issue that the timber bolts move a little in the bracket; that's the right one to use.

Mitchell

yeahboo

Hello @MitchellMc ,

Last weekend, I made some cuts for the frame (outside ones).. I followed your advice to make it square/rectangle.. so the measuremeants ended up

2 x 4110 mm = This was because I factored in the 45mm (from the 2x4700mm), and some allowance for the fascia board ~19mm but I made it 20mm (so width total is 4220mm

2 x 4700 mm = These 2 are on the "outside" of the square/rectangle, and a 20mm extra for the board...

What I noticed though is that it looks like the apron isn't straight (and timber as well) so there might be some parts of the cement showing towards the side near the fence.. Is this something that I should rectify now? or it's up to me if I am fine with a few milimeters of cement showing? or am I thinking too much and I should fasten the outer part first and see how it looks? Thanks!

EricL

https://www.workshop.bunnings.com.au/discussion/comment/35366#Comment_35366

Hi @yeahboo

The timber can be forced to straighten out using the angle brackets. I suggest putting the angle brackets in an alternating pattern one on each side. This will allow you to control the bend of the timber.

Your other option is to look through your timber set and search for the straightest one you have in the bunch. The best way to give yourself a guide is to set up a builder's line so that you know if the timber is sitting straight. I also recommend using a spirit level so that you'll know if the timber is level horizontally as well.

If you need further assistance, please let us know.

Eric

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/35366#Comment_35366

Evening @yeahboo

Id be thinking along @EricL's lines but I will add some thoughts 🙂

Rem you will have a "face" to the edge of the deck. this will cover up uneven edges and "fix" things that dont look quiet right.

I have very rarely found timber that is straight, usually there is a curve or twist.

You will find that the deck boards may have a bend to them, In this project you can see how I used a ratchet to help straighten them out Courtyard privacy fence and gate build, Part 2

I have found over the years that sometimes it is better to have things "look right" more then actually "be right" Its hard if you want it to be perfect but fooling the eyes can take a project that you are working with and cannot control the past edges a long way to looking right right.

Easiest way to hide the unstraight edge of the concrete maybe to have the low deck overhang the edge by a little?

Dave

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/146961#Comment_146961

Hello @MitchellMc ,

I followed this advice for the ones that will be "touching" the wall. The one thing I can't wrap my head around is, how will I attach the rest of the joists on this side if I drill/fasten this timber already in the concrete? Since the other side isn't exposed, I won't be able to drill it like the one you did in the video.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/147080#Comment_147080

Hi @yeahboo,

Ideally it would be best to create the entire frame shifted out a metre from the wall, so you have access to screw through the frame into the ends of the joists. Then, once completed, have a few mates assist you to pick the whole frame up and shift it back into position. However, your post might make this a little difficult.

Alternatively, you can use 90 x 45mm joist hangers.

Please let me know if you have any questions.

Mitchell

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/147187#Comment_147187

Hello @MitchellMc ,

I ended up following your advice to shift it away from the brick first and then move it back. PXL_20240329_051932325.MP.jpg

PXL_20240329_080731014.MP.jpg

I built it level while a few meters away from the brick. I noticed a few bent and twisted timbers so thoses ones aren't fully screwed with 2 screws. I am hoping when I put some timbers perpendicular to each joist (not sure what's that called), that they will "straighten" joists and I can complete the 2 screws...

If I want to have "picture" frame boards, I will need to put another timber on either side (left, and right parallel to the joists) right? Hopefully, I complete the frame before the long weekend ends

Thanks for all your help so far! also, any points you can think of that I may have forgotten are always welcome!

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/147279#Comment_147279

Great stuff, @yeahboo!

Adding those noggins will help straighten the joists.

You're correct that you need to add another timber/joist at either end so the decking boards can be fixed to it, and then you can add the picture frame. Have a look at step four in this guide: How to build a deck.

Mitchell

yeahboo

https://www.workshop.bunnings.com.au/discussion/comment/147364#Comment_147364

Hello @MitchellMc ,

Some minor challenge came up when I finally moved the whole thing to near the brick(towards doorway, and wall).. Since the concrete slab isn't even, some of the timber "touches" the slab a bit. Some, timber, maybe I can still put something underneath, but some are like this:

Any suggestions on how I will handle this? What should I do on the section that touches the slab?

Thank you.

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