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How to level and compact the ground before building a deck on top?

Hi,

I am looking for some advice on leveling and tamping the ground before building a deck.

After the plumber fixed the water leakage issue, a patch of my backyard has been left as shown in the photo. The patch is about 2x2m. I am planning to build a deck on top to 1) make a nice resting corner and 2) have an elevated platform to protect the PVC pipe down there.

My questions are,

1. What material should I use to fill and compact the area? Obviously want something to cover the pipes without putting too much load on them. The plumber suggested some soil and Tuscan on top.
2. What tools do I need for the project?

3. Any guidance for building deck?

Thank you.

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Decking and Paving

Building and Construction

Landscaping

Comments

Jewelleryrescue

Hi @leijiang

A deck is a timber frame with extra cross bearers for the top layer support. the underneath you can stand on bricks or stupms in the ground to raise it to whatever height you want.

The beauty is @leijiang no pre ground work required, no compaction no soil or any thing as your deck will cover it all and protect it.

Build a deck out treated pine sleepers frame 200mmx 50mm x 2.4 meters put in cross bearers and level the squre you made lifted to the right height adnd then your ready for addin a top deck.

Well thats for starter s what do you think you want to do now ?

MitchellMc

Welcome to the Bunnings Workshop community @leijiang. It's wonderful to have you join us, and many thanks for your question about preparing soil for a deck.

I'd suggest laying weed matting over the area and placing at least 50mm of drainage gravel over that. That way, any water in the area can easily seep through the gravel and drain away. Also, how's the drainage in that area? Does water run away freely or pool there? If it does pool there, it might be an idea to install a drainage pit to collect the water and send it into your stormwater pipe. Any standing water under a deck can cause high levels of humidity and the early onset of timber decay.

The only thing I'd qualify about using sleepers for a deck is that they are not structurally rated, and therefore, their use is not permitted on a weight-bearing structure like a deck. Instead, use H3 timber, which is suitable for above-ground use and place it on footers.

Please let me know if you have any questions.

Mitchell

leijiang

https://www.workshop.bunnings.com.au/discussion/comment/33168#Comment_33168

Hi @MitchellMc

Thank you for suggestion. A few follow-up questions

1. The drainage in this area is fine, never seen any pooling water. The area is a bit bumpy but not necessarily deeply sunken. I've attached a photo hopefully to make it clear. The area circled has the deepest spot about 40mm depth, while the surrounding is pretty ok. If I place 50mm gravel on top, would that be too much and need some sort of edging?

2. What type of gravel do you recommend to use? fine screenings or some crushed rocks?

3. On top of gravel, do I need to lay some sand as well? Some says this will help with leveling and compaction.

4. For decking, H3 timber as bearer?

5. I've watched Bunnings deck building DIY videos, are you suggesting to use footers vs stumps to support bearers? Footers seem easier as it removes hole digging and concrete.

Sorry for the barrage of questions. First time taking a challenge to build a small deck myself.

Appreciate your advice.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/78909#Comment_78909

Hi @leijiang,

Drainage gravel is fine to use over that area. A layer of 50mm thick across the whole area should be fine, or you could just level the area with the gravel. It doesn't need to be a full 50mm above the height of the surrounding area. That drainage gravel is 10-20mm. Sand on top of it would help with levelling the area, and a paver and an adjustable pedestal foot for each support will allow you to account for an unlevel surface.

H3 timber is what you'd typically use as a bearer.

A footer is what goes in the ground, such as concrete, to secure the stump in place. You can use concrete footers and stumps, brackets, or a paver on top of the soil and adjustable feet. Sorry, I misspoke previously; that was a concrete foundation, which is also another option.

Mitchell

leijiang

https://www.workshop.bunnings.com.au/discussion/comment/103736#Comment_103736

Thanks @MitchellMc

Just to clarify the last piece. A footer is to secure stump not bearer?

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/118912#Comment_118912

It depends on how high your deck is, @leijiang. Typically, you'd concrete a stump into a footer for an elevated deck. For this situation, if the bearer is less than 200mm from the ground, I'd go with a paver and pedestal feet. Generally, you wouldn't place a bearer on a footer, but you could concrete a stirrup into the footer and place it on that.

Mitchell

leijiang

https://www.workshop.bunnings.com.au/discussion/comment/127968#Comment_127968

Thanks @MitchellMc.

One more question, for the drainage gravel, how many cubic meters is a bag? I'm trying to come up with how many bags do I need.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/133880#Comment_133880

Hi @leijiang,

Could I please have some more context to your question? Are you trying to determine how many bags you'd need per square meter? If so, that would be around three to four. There's no equation I can use to work out how many drainage gravel bags are in a cubic meter.

Mitchell

leijiang

https://www.workshop.bunnings.com.au/discussion/comment/137553#Comment_137553

Hi @MitchellMc

Yes I’m trying to work out how many bags are needed to fill a cubic meter? My patch is 2x2m if I’m going to lay 50mm gravel, that is 0.2 cubic meter, so just wonder how many bags I need.

Thanks.

MitchellMc

https://www.workshop.bunnings.com.au/discussion/comment/140071#Comment_140071

Hi @leijiang,

A 20kg bag of gravel doesn't have a labelled volume, so I am unable to provide an answer to how many bags are in a cubic meter. It's widely accepted that you'll need around three to four 20kg bags of gravel per square metre to establish a layer of 50mm. So, you'll need around 12-16 bags for your project. I'd grab at least 14 and return any extra you don't need.

Mitchell

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