How to build deck over concrete and soil?

[JesseS6]

Hi All,

I think I have finally finished my design for my deck which will be half over concrete and half over soil.

Over the concrete I have 180mm to the top of the brick. I will be using 140x19mm merbau. For the joists I plan to use 140 x 45 Pine set 21mm off the concrete using Zinc Plated Reinforcing Angle Bracket with the joist. I will Dynabolt these using a DynaBolt Plus Hex Nut to the concrete every meter or so.

The joists have 355mm centres, I will just use a nail gun to fix these every 1m along the joists.

Over the soil, I will dig out about 300mm and put down crushed rock and ag pipe for drainage. The posts will concrete in 300mm and out 320mm. With bearers cut in. I will be using 190 x 45mm Bearers with 1218mm spacings. The posts will have 1000mm spacings.

The deck will also be a picture frame deck.

I have drawings below, please provide any comment, or issues, corrects, errors you may notice.

[MitchellMc]

That's looking pretty good @JesseS6. With the brackets connecting the joist to the concrete, alternate the side they are on going down the joist. The first one on the left side of the joist , the next one on the right side. This will make it much more stable than all being on one side.

For the noggins, you should space them more evenly along the length of the joist. You've got them all in the middle, whereas they would strengthen the structure better if they were spaced out as per the below. 

Mitchell

 

[JesseS6]

Is it fine to just use nail gun to fix the noggins? 

[EricL]

Hello @JesseS6 

It's perfectly alright to use nails for the noggins. However, if you have a choice in the matter, I suggest using screws instead. Screws are strong and are built to last. This is a stark contrast to nails, which may come loose over time. This happens when the materials they connect with begin to expand and shrink over time. Screws are built to resist this problem.

If you need further assistance, please let us know.

Eric

[JesseS6]

Thanks @EricL 

Also am wondering if the post need to be sunk in the concrete. Are there any issues with setting a post anchor and attaching the posts to those? or something similar? what other options are available?

[EricL]

Hi @JesseS6 

From a construction point of view, it would be best to sink the post into concrete. Building a concrete footing and anchoring into it is like double handling and you have to spend for the hardware to attach the post to the concrete footing. Building it as one piece means that won't have to go back to it again. The other options are pedestal bases, concrete foundation blocks and Tuff block footings. These options will require you to add paving bases and shims to level and square.

If you need further assistance, please let us know.

Eric

[JesseS6]

Hi Eric,

In regards to the other options highlighted. Are these all seperate options? and would I require posts for the bearers or have these level so the bearers can sit straight on.

I assume by paving bases, its not just a paver but roadbase compacted then paver? do you have any illurstrations of these?

[JacobZ]

Hi @JesseS6,

Yes, the pedestal feet, concrete foundation block and TuffBlocks are all different, but almost identical in their function. 

It's usually best to add compacted road base as it is an easy way to ensure the pavers don't move and create a level surface for your pedestal feet, concrete foundation blocks or TuffBlocks to sit on. 

Getting the foundation for your supports nice and level will make the supports level, which in turn makes your bearers level. Fine adjustments can then be made with packers on top of the pedestal, foundation block or TuffBlock and underneath the bearers.

Let me know if you have any further questions.

Jacob

[JesseS6]

@JacobZ Thanks for the response.

The road base would need to have a slight fall for drainage. Would using mortar under the pavers assist in keeping them level? 

When you say packers, what are you referring to?

[JacobZ]

Hi @JesseS6,

No, the road base would not need to have a slight fall for drainage. Road base, as a material, is porous, allowing water to drain through it, so there is no need to add a fall for drainage.

Yes, adding mortar under the pavers would help you to adjust them to level your pavers. You don't need to add mortar, but it can make the levelling process a bit easier.

When I said packers, I was referring to window packers. They are small pieces of high-density plastic that can be sat underneath your bearers to lift them that little bit to make things perfectly level.

Let me know if you have further questions.

Jacob