Low Deck Build - Tuff Blocks on pavers

Medjumurac · Dec 18, 2023 6:31 pm

Hi folks,

I'm looking to setup a new deck in my small back/court yard and I'm trying to do it with as little fuss as possible. I've attached an image here that shows the current state of the area. Bunch of pavers and some very clayish soil.

To avoid having to pull up the pavers and dig/concrete 8-ish holes, I was hoping I could get away with a combination of Pryda stirrups in concrete in the dirt area, and Tuffblocks (product from Bunnings) on the pavers. I've attached another image with what I'm going for.

There are a couple of issues I can see that I just wanted to run past the community:

You might notice from the pictures that there isn't a lot of clearance between the top of the pavers and the sliding door. To get around this, I thought about using 90x45 treated pine as the bearers/joists. With the 50mm height of the Tuffblock and ~19mm from the decking boards, that's a total height of about 160mm - but will 90x45 be strong enough for the deck?

According to my understanding of span tables, it's acceptable as long as Iong as there's no continuious span over 1600mm.
The pavers are unfortunately a little uneven. They fall very slightly toward the shed, and very slightly toward the house. It's not enough of a difference that I can use posts to offset - is there anything else someone can recommend? A shim maybe?

Thanks in advance for any help you guys can give.

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ponzutwo · Dec 20, 2023 3:31 pm

the 90x45s should be fine in your application. Realistically the structure doesnt appear to be significant enough to be of concern to the various other things you're compromising on (part stirrups/tuff blocks, wierd slopes etc.)

What software did you use to sketch this up and overlay over a photo? I like it.

Medjumurac · Dec 20, 2023 9:00 pm

ponzutwo

What software did you use to sketch this up and overlay over a photo? I like it.

I used SketchUp to create the actual 3D stuff and then just dropped it into photoshop after trying to line up SketchUp. Probably a little much but I really wanted to get across what was in my head.

supersleuth · Dec 21, 2023 4:49 pm

I agree I was impressed with your drawing in 3d. Thought you must have been a graphic designer to whip that up.

Regarding the deck, i've done a couple of low clearance decks and I'd just suggest up spec your treatment rating - use H4 timber so it can cope with sitting in damp/water. I've used 90x45 with no issues/flex as long as the span isnt too large.

Personally i'd be inclined to remove some pavers and concrete some posts into ground rather than attaching to top of pavers

Maybe even consider using composite decking to avoid risk of decking boards rotting given limited airflow potential.

Medjumurac · Dec 21, 2023 6:20 pm

Yeah I am leaning back on removing the pavers and concreting in some stumps or stirrups.

The question is what can I get away with that'll reduce the amount of digging and mixing I have to do. At the risk of overplaying this 3D thing, I'm thinking about something like the attached image. I know it's pushing a little with only 3 stirrups, but according to the Demak span table PDF I should be OK if I'm using 140x45 - or at least that's my understanding of it.

It is a small deck, and there won't be much weight on it at any given time. Might put some of the TuffBlocks underneath at various points along the bearer and some of the joists for extra strength though.

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ponzutwo · Dec 22, 2023 8:07 am

Personally i wouldn't be looking to minimise anything. Get a posthole digger for the holes, will make the job much easier. On the concrete mixing, just get a mixing attachment for your drill and mix up in a bucket. Both those workflow solutions make the job 100% easier.

supersleuth · Dec 22, 2023 12:58 pm

Those span tables can be pushed a little for a low deck if you dont mind a little flex. Last deck I did, I pushed it a little and it was still rock solid - no noticeable flex.

You might save a fair bit by going down from 140x45 to 90x45 joists and just doing a few more holes.

Also given its almost ground level deck, assuming the soil is natural ground and undisturbed/heavily compacted, I reckon you could easily reduce hole depth/digging to 300mm. That will save a fair bit of work and concrete.