What joist size to use for low-level deck?

[Zog]

Hi everyone. I have assembled the framing of the modular decking for my low level deck (see photos). What is in the photo is essentially a walkway, the main deck will be under the pergola and slightly higher. I've gained some confidence from what I've done so far and am considering using tuffblocks and building a framework rather than using the modular decking for the main deck. My question is just about the joist size. I'm not going to use a bearer and joists system, just a framework of joists, mainly because the Pergola is already there (before I bought the house) so I need to preserve the ceiling height of the pergola as much as possible.

I'm unsure about joist size and span of tuffblocks. The Tuffblock website has an article where they're using 2"x6" (45x150) joists, I've seen joists of 45x90 used in Australian based articles and the joists of the Good Times modular panels from Bunnings are 45x70. I'll probably use 140x19 merbau decking.

The pavers will be staying, they're not perfectly level, a small part of the deck will be on soil (the far sides in the second photo).

The total size of the main deck will be about 6.4m x 7.4m or 47.36 m2. It's a lot bigger than any articles I've seen about building a  low level deck. Any advice will be much appreciated.

[EricL]

Hello @Zog 

I strongly suggest doing it in sections and at your own pace. 

Please keep us updated with your progress, we look forward to seeing your deck panels installed.

Eric

[Zog]

Hi @MitchellMc 

after having a holiday I'm back to working on the deck and have a question.
there are horizontal screws in the framing and when screwing the decking boards on the outer edges of the walkway the decking screws are hitting these horizontal screws and the same thing will happen on the main deck. I've tried to find a shorter Simpson strong-tie 12G, eg a 5.5x35mm that I could use on the outer boards, but couldn't find anything. Is there a shorter suitable screw that has a similar looking head (so that mixing them won't look too bad) ? I've cut a few screws shorter but it is very time consuming (more than 100 screw) and a shorter screw would be easier.

[JacobZ]

Hi @Zog,

These Buildex® 8 - 10 x 40mm Zinc Alloy 3 Trim Head Timber Screws are the only ones I could find that are shorter and have a similar head.

Alternatively, I have two other options you could try. 

Try taking the screw out and angling the decking screw slightly so it slips past the horizontal screw. A slight angle will not be obvious when the head screw has been driven unless you go looking for it. 

You could also remove the decking screw and drill through the horizontal screw with a drill bit that is slightly smaller than the shaft of the screw. With some pressure, the decking screw should drive through the horizontal screw. 

Let me know what you think.

Jacob

[Zog]

Hi @JacobZ 

They're all good suggestions. I think the screws will be the best idea. I'll check them out tomorrow.

Thanks.

[Zog]

Hi Guys,

when the joists were delivered a few weeks ago, I mentioned that some of them were curved and twisted and @MitchellMc remarked that I may be able to get a replacement.

I'm pretty sure that most of them are usable but the one in the photo has an S bend and is twisted. You can easily see the curve in the photo but the S bend is a bit harder to see - the curve reverses just past the middle and the twist is in the last 1-2 metres..

I don't think this piece is usable except maybe as noggins.

Is it possible to get a replacement ?

[JacobZ]

Hi @Zog,

Yeah, unfortunately, that joist is too twisted for use as a joist. If you had noggins to install, you could definitely use it for them, but it would not be suitable as a joist.

As timber is not always perfect, this is a situation that our stores come across frequently. Assuming you still have your receipt, there'll be no issues returning and replacing this timber. Just head to the trade counter in your local store, explain the situation and they'll be able to swap it over.

Let me know if you run into any issues, I'm happy to assist if required.

Jacob

[Zog]

I have no way of transporting a 6 mtr joist.

[MitchellMc]

Hi @Zog,

I suggest you contact the trade counter at the store that delivered the timber to you. Let them know that one of the lengths is unusable and you cannot transport it yourself. I trust they will do their best to replace it for you and send another out.

Mitchell