What would be a suitable bearer for a very low profile deck?

[Auyon]

Hi Mates,

I want to build a deck in my backyard. I have a pergola there. I have existing pavers there and thinking of building the Deck on top of the pavers.

The problem is the height. To match with the house, the deck must have a height of 65mm.

I did a rough design of the deck using an online tool. Although the tool is showing joists over the bearers, but I think using joists between bearers will be fine. I was thinking of using PB-0-S18 (18-28mm) from Pascoe Constructions (https://pasco.net.au/products/pb-0-s18-18-28mm/ ) and DPH joist holders. It is the smallest base that i could find. 

With the height of the base (18mm) and that of the Deck (19mm - SpecRite 90 x 19mm Pre-Oiled Select Grade Merbau Decking), I need a bearer with a maximum height of 28mm. 

I was wondering - 

-  if this very low height would create any problem for the deck (the pergola has a roof)

- what would be a suitable bearer and joist?

I

Thank you mates for your help.

Auyon

[MitchellMc]

Welcome to the Bunnings Workshop community @Auyon. It's a pleasure to have you join us, and many thanks for the question about your deck plan.

All your timber will be in very close proximity to the ground, and if any moisture gets into the deck, you should expect its lifespan to be shortened. No airflow and moisture cause rot. However, your deck is covered, which is less of a concern than one exposed to the weather.

It would be my advice to remove the pavers where the feet need to be located. You'll then have more room to work with, and an appropriately sized bearer can be used.

You're not going to find a bearer of less than 35mm to use with your current plan, so I'd suggest changing it. An alternate option could be to use 90 x 35mm H3 MGP 10 Treated Pine Outdoor Timber Framing on its side and packed up to the appropriate height with plastic shims. Dynabolting through the face of the timber into the pavers would secure it. Obviously, it is not ideal to fix into pavers, though the extremely low-level nature of this deck makes it fairly unique in the first place. Many of these plastic support feet systems aren't designed to be fixed down and just sit on the pavers. So, if a free-floating deck is ok, I can't see much difference between them and fixing into an unideal location.

Please let me know if you have any questions.

Mitchell

[Auyon]

Thanks a lot @MitchellMc for your thoughtful suggestions. I especially like the idea of using plastic Shims. So in this case ther won't be any plastic support feet, only the shims? 

I am not sure if the pavers that I have here can be dynabolted. I am not much of a DIYer myself and I haven't done it before. In a previous occassion when I was adding a drainage pit, some of the pavers broke very easily, just with a small hit of hammer. So my confidence level of driiling/hitting them is extremly low. 

On the other hand, there is soil beneath the pavers. so if I remove pavers to place the plastic feet, do I need to use concrete to fix the feet? 

How about if I use Floor Decking like Ikea Runnen (https://www.ikea.com/au/en/p/runnen-floor-decking-outdoor-brown-stained-30234229/)?

Thanks in advance for your help.

Auyon

[MitchellMc]

These plastic support feet as essentially fancy shims @Auyon. As long as the joists are framed in around the perimeter, and some noggins are installed between them, the structure will sit on top of the shims. 

You could try one of these Multi-Max Multi-Material Drill Bits. They'll drill into masonry without the hammer function. That might prevent cracking. However, I think the best solution would be to remove the pavers and work with the soil. If the soil is solid, which I presume it is, the feet can be placed directly on it with no concrete needed.

Floor decking would be an option in such a limited space. Bear in mind, with that type of timber tile; there's virtually no airflow under it.

Mitchell

[Auyon]

Thanks again @MitchellMc . You are absolutely right - those are fancy shims, hahaha. So if I use the shims for both the bearers and the joists, and install noggins between the joists, that would do the trick! Since the deck will be fairly large (4.2m X 4.8m), will the weight of the deck be enough to stop it from moving? 

Thanks for your help.

Auyon

[EricL]

Hello @Auyon

The combined weight of the frame and decking panels should keep the deck from moving. However, if you feel that an added anchor would be a safety feature, I suggest putting in a cemented timber footing on each corner of the deck. I would anchor these four posts onto the frame at the very end to make sure that the frame is level. 

If you need further assistance, please let us know.

Eric