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How to build a curved deck on soil?

Hi all,

Motivation

I'm Chen and plan to build a curve decking in my front yard to replace the existing lawn. The area faces north/west and does not receive sunlight well during winter due to the Sun angle and the surrounding trees, the lawn wasn't very well maintained either, hence why I'm starting the project. I've designed the layout in Sketchup and would like to hear some ideas and feedback for my plan.

Plan

The site dimension is about 7.9m x 3.6m, detailed dimension is in the SketchUp plan down below.

I'm planning to build a floating foundation using decking foot e.g. TuffBlock or similar products. As there's one mature Jacaranda tree and two cypresses surrounding the area, I'd avoid digging post holes and concrete.

Plan to use 90 x 45 H3 timber for framing with 450mm spacing apart. Decking foot will be laid 1000mm apart.

The project will require quite a bit of cutting to fit with the curve side along the garden bed. I will picture frame rest of the edges.

SubframeDecking board laidBottom viewFlow to existed pathway

Current Progress

I've stripped grass, leveled the soil, and compacted with a hand tamper. Next step is to lay some weed mat and road base for decking foot to set on.

Questions

1. I've read multiple projects using TuffBlock but most of them don't concrete or mortar the decking foot. Do you think I should provide a mortar bed for the foot to set on?

2. One of the tricky things is I'd try to set the decking finish height flush with the existing sandstone pathway, which leaves the smallest ground clearance to 50mm, I'm wondering if this is enough.

3. I've been suggested by a friend to use RoundUp to kill the weeds and lawns, he mentioned there's a chance for weed to grow on top of weed mat in the future when dust/soil accumulate. Personally, I don't prefer the RoundUp method as it would potentially affect the tree roots. What do you guys think?

4. Do you think my decking footing spacing (1000m) is enough? Any comments on my plan?

Any ideas and thoughts are welcomed!

Thanks

Chen

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Decking and Paving

Building and Construction

Landscaping

Comments

MitchellMc

Welcome to the Bunnings Workshop community Chen (@southpolemonkey). It's wonderful to have you join us, and many thanks for your question about constructing a deck.

It sounds like you've done your research.

In answer to your questions:

1. Tuffblocks only require a compacted base. There is no need for a mortar bed for the foot to sit on. If you are concerned, you can use a concrete paver to distribute the load over a larger area.

2. 50mm isn't enough height for your Tuffblock and joist to fit within. Consider reducing the soil height to accommodate or have a step up onto the deck.

3. Weedmat will prevent weeds from growing up from the soil below, so there is no need to spray Round-up. There is a chance that weeds could grow up from debris sitting on top of the weedmat, but I believe the amount you'd see would be minimal.

4. Your joists need to be supported every 1000mm. Connecting joists together isn't adequate support. I've identified some areas of concern where I think you need extra support. I know it seems like a lot, but currently, there is nothing supporting the areas marked with stars.

Please let me know if you have further questions.

Mitchell

southpolemonkey

https://www.workshop.bunnings.com.au/discussion/comment/26284#Comment_26284

Hi @MitchellMc

Appreciate your reply.

Re 2. I used the wrong term. What I meant was the gap between the soil and the bottom face of the joist is 50mm, which is the minimum height of TuffBlock.

Thanks for pointing out the extra joist support, I will revise my plan.

southpolemonkey

https://www.workshop.bunnings.com.au/discussion/comment/26284#Comment_26284

Hi @MitchellMc

I'm starting this project and need some advice on connecting noggins between joists.

My plan is to use 75mm stainless batten screws to connect perimeters for a strong connection but think about nailing the noggins to speed up the process.

Could you give me some advice on what type of nail gun and nails I would need? Cheers

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/76032#Comment_76032

Hi @southpolemonkey,

The Paslode Impulse Frame Master Gas Nailer and 75 x 3.06mm Hot Dipped Galvanised D Head Impulse Nails would do the job for you. That would certainly speed up the works.

Remember to wear appropriate PPE, including safety glasses and hearing protection.

Please let me know if you have further questions.

Mitchell

southpolemonkey

Hi, I'm started my decking project over the weekend and the longest joist span over 7m and I need to join two 90x45 to make that length. I use tuffblock as footing and butt joint two joists over it. How should I connect these two parts together? Would a nailplate work?

Cheers

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/26903#Comment_26903

It's great to hear you'll start your decking project over the weekend @southpolemonkey.

The Tuffblocks accept up to a 47mm joist. Since you'll be using 45mm joists and two nailing plates, one on either side of the joist, that will exceed the maximum capacity if the straps extend out past 100mm. You'll need to use a nailing plate that occupies only the blue or red sections I've highlighted below. Given that you'll be using noggins in your design and that the joist ends are sitting on the block, a Pryda Strap Nails 50 x 100mm in the red section should be sufficient. There will be an additional space above it where you could fit a Pryda 25 x 100mm Strap for extra support if needed.

Please let me know if you have further questions.

Mitchell

southpolemonkey

https://www.workshop.bunnings.com.au/discussion/comment/76122#Comment_76122

Thanks @MitchellMc for the quick reply.

I also changed my plan to use a bearer at the lower spot and let joists sit on the bearer. I used 90mm H3 should for the 100mm height difference between my finish height, I think using 10mm window packs to compensate gap could be a solution.

What do you reckon is the best way to tie down joists to bearers? Would screw down with an angle provide enough strength?

Cheers

EricL

https://www.workshop.bunnings.com.au/discussion/comment/101931#Comment_101931

Hi @southpolemonkey

I suggest adding a joist strap in combination with screws placed on an angle. My other only suggestion is to test the layout first making sure that your footing is secure and supporting the timber frame above.

If you need further assistance, please let us know.

Eric

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