Workshop
Ask a question

The Bunnings Workshop community can help with your home improvement projects.

Ground level low-profile deck

tavo1421
Growing in Experience

Ground level low-profile deck

Hi everyone,

 

I want to build a deck of around 14m x 1.3m on one of the sides of my house.
I checked many forums, websites and post here and there. I learned a lot but I still have a lot of doubts. Most of the information out there is about huge decks built in which I guess are cyclonic areas or with extreme weather conditions like snow, etc. I live in NSW and I think a ground-level deck could be somehow much and simpler, with fewer components while remaining robust and compliant with the local standards.

As you can see in the pictures below, the area is next to the neighbor lot. Also, I need to dig out some centimeters (maybe around 20'ish cm) in order to make the deck flush with the terrace and side entrance. Currently, there are 4cm between the terrace level and the soil.

  • Do I need to leave a gap between the colorbond fence and the deck?

decking-area.png 

From my understanding, the classic deck structure has concrete pads, some sort of galvanised stirrup like this, posts, beams, joists and the decking board. In order to make it flush with the terrace, If I use all the above, I will need to remove a lot of dirt . 

For instance, I was thinking of using like a 300mx300m concrete pad, galvanised stirrup on top of it and then beams and joists at the same level like the following (sorry for my draft 2d/3d sketch). 

draft.jpg

What would be the minimum required components for a low-profile deck? Which brackets are appropriate for a low-profile deck without posts?

 

Providing that I need to remove some dirt next to the fence sleepers (see img below) they used to level up the fence:

  • I wonder if it could somehow collapse. What can I do to prevent that? 

sliding-door.png

 

Last but not least, can someone (@MitchellMc ? :laugh: ) help me to calculate the beams/joist and concrete pad needed based on the above deck dimensions?

 

Cheers,

Tavo

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Ground level low-profile deck

@tavo1421,

 

Did you ask them for the soil reactivity classification? It doesn't match with the table because I'm fairly sure it's not the information you were after. Different levels of acid sulphates in soils can affect concrete foundations, but I don't believe it has anything to do with the footer's required size.

 

You'll need to be quite specific with telling them what information you require. Keep in mind they might not know what the soil type is. 

 

Unfortunately, most building codes have an attached price tag to them. If you employ the services of a professional, then they will have them on hand. If you search for the specific information you need from the codes, you'll find sites that have partially copied information from them. The tables I have provided above are an example.

 

Mitchell

 

See something interesting? Give it the thumbs up!
tavo1421
Growing in Experience

Re: Ground level low-profile deck

Hey guys,

 

Finally I did some progress with the excavation and prepare the terrain for start doing this.

I would like to check with you some doubts I have regarding screws and bolts:

For fixing decking board (90x19mm Merbau) to the treated pine, do you think 50mm 10G screws are ok?

In terms of the screw type, do you recommend stainless steel like this or the specific ones for treated pine like this, this or this

 

For bolting the treated pine to the stirrup, which bolt size and type do you recommend?

 

Finally, to secure the joists to the bearers with the triple grips, I guess I should use nails, right? which type and size do you recommend?

 

Cheers,

Tavo

 

 

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Ground level low-profile deck

I'm glad to hear you've started on your project @tavo1421.

 

It would be my opinion that the Zenith 10G x 50mm Stainless Steel Type 17 Countersunk Rib Head Decking Screws - 500 Pack would be the best option for your project. Not only do they have fantastic corrosion resistance, but they look amazing too. 50mm x 10G screws are a suitable calibre for fixing your decking boards.

 

Have you decided on what dimensions the treated pine being bolted into the stirrup will be? You'll need a bolt of approximately 8mm thickness that is long enough to pass through both the timber and the stirrup. So, if you were going to use a Pryda Post Anchor Half Stirrup Solid Stem 300mm M10 carrying Treated Pine Outdoor Timber Framing 140 x 45mm, you'd need a Zenith M8 x 60mm Hot Dipped Galvanised Cup Head Bolt And Nut.

 

Pryda does their own 35 x 3.15mm Timber Connector Nails for fixing all their bracing and timber connectors. You might find the Pryda Joist Hanger Suits 45 x 90mm a better option for connecting the joists to bearers than triple grips.

 

Please let me know if you need further assistance or have questions.

 

Mitchell

 

See something interesting? Give it the thumbs up!
tavo1421
Growing in Experience

Re: Ground level low-profile deck

Hey Mitchell,

 

I will use 90x45mm for both bearers and joists in a single layer. So, I guess the bolts are the same, right?

 

Thanks for all the info!

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Ground level low-profile deck

That would be correct, @tavo1421. The 45mm thickness is the same, and a 60mm bolt would be sufficient.

 

Please keep us updated and remember to take lots of pictures of your progress.

 

Mitchell

 

See something interesting? Give it the thumbs up!
tavo1421
Growing in Experience

Re: Ground level low-profile deck

Awesome, thanks again.

Regarding the joist hungers. The bearers are centered to the footer, so there is a gap between them and the wall. In order to secure the decking boards which will be close to the wall I would need to somehow extend the decking structure. My idea is to add some small joists to the external side of the bearers (see pic). I wonder if that's the way it is usually done? or it's needed a halved joint between the joists and the bearers? There are 33 joists and 2 bearers in my deck so not too happy to do 66 halved joints :smile: so maybe the "small joists" could be a (lazy) alternative. If that's the case, do you recommend to use joist hungers again to secure them to the bearer or I could just use two/three timber screws from the other side of the bearer?

 

joist-ext.jpg

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Ground level low-profile deck

Hi @tavo1421,

 

If it is a brick wall, you could consider bolting the bearer directly onto the wall instead of being supported by posts. This is done when footers can't be placed close enough to the wall. The bearer is then called a ledger, and the wall supports the deck. Below I've illustrated a hybrid method, where you still keep the posts and bolt a secondary ledger to the wall bridging the gap. However, you can leave out the posts completely.

 

Although your method would most likely work, having one end of the joist unsupported like that isn't recommended. 

 

Please let me know if you have questions.

 

Mitchell

 

 

See something interesting? Give it the thumbs up!
tavo1421
Growing in Experience

Re: Ground level low-profile deck

Thanks for your response.

Yeah, I was trying to avoid to drill the wall and bolt the ledger to the house, but it would make everything easier, less footers and it will probably be more robust.

As it's the house foundation, it's actually concrete, see pics below.

 

I would need to know how to do it properly because don't want to cause any damage to the foundation. I would appreciate any guidance or advice on this.

 

PXL_20210303_002632513.jpgPXL_20210303_002636577.jpg

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Ground level low-profile deck

You'd drill into the concrete foundation with a masonry drillbit @tavo1421, and I can't see any way you could damage the foundation. A Dynabolt can then be used to fix the ledger board to the foundation.

 

If you need to go through the tiles, that might be a bit different. Cranking down on the Dynabolts could crack the tiles. It's just an option that I thought you should know about. Will those tiles on the side of the foundation be visible after the deck has been constructed? If not, you might consider removing them.

 

Mitchell

 

See something interesting? Give it the thumbs up!
tavo1421
Growing in Experience

Re: Ground level low-profile deck

Thanks @MitchellMc for your response.

 

Well, the deck has to be flash with the top of that step/tiles, so the ledger should be 19mm (decking board width) below that line. That means that the bolts will need to go through those tiles in that part of the wall. There are other parts of the wall where there is brick at that height and concrete below. You can see that in the picture I posted in the first message of this thread. 

Any idea of how many bolts, size and distance between the bolts? 90x45 for those ledgers should still be ok?

 

Those dynabolts are the ones you hammer through the hole and they expand, then you use a nut to fix it to the ledger, right?

 

 

 

Why join the Bunnings Workshop community?

Workshop is a friendly place to learn, get ideas and find inspiration for your home improvement projects