Workshop
Ask a question

Low-level composite deck

oninpena
Having an Impact

Low-level composite deck

deck.pngHi,

I am planning on putting a low level composite deck on my alfresco.  I have attached some photos of the alfresco where I plan to put the decking. 

 

I plan to build it on top of the concrete and apron, and part of the deck would also be on the soil at the side of the house.  Please see the last photo/drawing of where I plan the deck to be (second to last photo is a render of the alfresco area without deck)

 

Questions:

1. In the first photo below, there is an opening/pipe/drain on the concrete apron.  Can I build the deck over this?  Is there going to be a problem?

2. On the third photo, you can see the part that has no concrete, what can I put here to support the deck? Can I use pavers and try to level it with the concrete apron?

3. I've read a lot of discussions on raising the joists from the concrete.  The height of the internal floor from the alfresco floor is 140mm.  If I use 90x45 TP + 23mm deck (Ekodeck) that leaves me with 27mm gap.  Can I use angle brackets to raise the joists to ~27mm?

 

Thanks you in advance to those who will respond!

 

Alfresco_1.jpgAlfresco_2.jpg

 

Alfresco_3.jpgTop View.jpgTop View Plan.jpg

Re: Low Level Deck Advice and Suggestions Pls

@MitchellMcgot another question. So I'm going to add more supports on the part of the deck over the soil using the builder's edge bigfoot.  Is the below plan ok, particularly the end where would be an overhang?

 

oninpena_0-1638166435871.png

 

EricL
Bunnings Team Member
Bunnings Team Member

Re: Low Level Deck Advice and Suggestions Pls

Hi @oninpena

 

How much of an overhang are we looking at? Please measure from the middle of the foot to the outside of the overhang? Once you give us that information, we'll be able to tell if you need to reposition the pedestal feet. 

 

Eric

 

See something interesting? Give it the thumbs up!

Re: Low Level Deck Advice and Suggestions Pls

Hi @EricL , overhang would be at 284mm.

Also, what size screws can I use to fix the timber to the pedestal feet?

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Low Level Deck Advice and Suggestions Pls

A counter-levered section of 284mm sounds like it would be fine @oninpena. However, if you're looking for exact building code regulations, I don't believe that is how the framework should be constructed to support the counter-lever. In the image below, I've added an appropriate overhang where the joists continue out to the end on the left-hand side. The solid joists support the overhang and, for it to fail, four joists would need to break. In your design, the overhang is purely supported by fixings, and this isn't acceptable as far as I can tell. The two stars indicate the only solid timber which extends out to the end of the overhang.

 

You should consider running your joists in the other direction if you want an overhang there or positioning the pedestal feet where you had them previously.

 

The pedestal feet can be secured to the timber with standard timber screws.

 

Mitchell

 

See something interesting? Give it the thumbs up!

Re: Low Level Deck Advice and Suggestions Pls

Thanks @MitchellMc .  I'll put them back to the last timber like below, the second to last joist should be ok without supports right?

 

oninpena_1-1638220578593.png

 

 

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Low Level Deck Advice and Suggestions Pls

You're now doing a combination of the two, and it doesn't appear to be solving the underlying issue that you are leaving areas unsupported @oninpena.

 

We might need to go back to discussing why you're positioning joists in specific locations. What was the purpose of the overhang section? I initially presumed you were doing the double joists at the end to be able to nail off your picture framing. I then suggested you add spacers, which would have connected the two last joists solidly, and you could have used one set of supports over that area. Since then, you appear to have turned those connected joists into an overhang. Whether you position the feet under the deck and have an overhang or position the feet at the exterior joist, it doesn't solve the issue that you leave one joist unsupported over its space. You can add a spacer between two joists and laminate them together with screws, but you can't join joists together with lengths of timber. I'll highlight the unsupported section below. If the fixings here fail, the deck collapses. You need timber bearing the weight of the deck, not just fixings. If you constructed it like this, that unsupported joist would sag.

 

You've previously mentioned this area is 1370mm wide. You'll fit three equally spaced joists at around 450mm in that space. That sounds like the best approach. If you need an additional timber to nail the picture frame off to, that can be laminated with spacers to the last joist. Have a look at the deck I'm building below. You'll see I've equally spaced my joists and then added an extra timber for the picture frame.

 

Mitchell

 

span.pngDeck space.jpg

 

See something interesting? Give it the thumbs up!

Re: Low Level Deck Advice and Suggestions Pls

@MitchellMcthe below illustrates what I plan on doing for the boards, there will be two end boards.  I had to change the design to reduce wastage of the ekodeck boards.

 

oninpena_1-1638223577495.png

 

As for the overhang, I was thinking of putting fascia boards to make a frame around the edges of the deck, like below.  If the pedestals are on the end then I would need to cut the fascia boards. Was thinking of the best way to do this without cutting the board, hence the overhang.

 

oninpena_3-1638223799936.png

 

So the below should be the best way to approach this. 

 

oninpena_4-1638223962736.png

 

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Low Level Deck Advice and Suggestions Pls

What will be the height at the end of the deck from the top of the joist to the ground @oninpena? Is it higher than 114mm? 114mm is the length your fascia board will drop below the top of the 90mm joist. 23mm of the fascia board will be above the joist. If the bottom of the fascia board is above ground level, then the base of the pedestal foot might fit underneath the fascia, so you don't have to cut it. Alternatively, you could put a spacer on top of a Builders Edge 35 - 60mm Smallfoot Pedestal Feet to achieve your 70mm height, and its base is much flatter.

 

Your pebbles would then cover the base of the pedestal foot, which is exposed.

 

Due to the predicament of needing those two picture frame boards, your layout above would be the most solid solution so far. Both joists here are equally supported. 

 

Mitchell

 

See something interesting? Give it the thumbs up!

Re: Low Level Deck Advice and Suggestions Pls

@MitchellMc the height is more than 114 mm.  the issue will be at the base where the timber rests on the footing like below.

 

oninpena_0-1638227988716.png

 

Can I do the below by adding a spacer where the red box is?  If not, then I'll just have to cut the fascia, it's going to be close to a retaining wall anyway, so not that big of a deal if it does not look perfect.

oninpena_1-1638228160050.png

 

 

MitchellMc
Bunnings Team Member
Bunnings Team Member

Re: Low Level Deck Advice and Suggestions Pls

You could run another full length of timber there @oninpena. Just screw two lengths of timber together and place them on the pedestals. Screw the closest one to the tab in. As far as I'm aware, those connection tabs don't serve any real structural purpose apart from connecting the foot to the joist to stop it from moving around. 

 

Mitchell

 

See something interesting? Give it the thumbs up!

Why join the Bunnings Workshop community?

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