How to build low level deck over concrete and grass?

[rwa1994]

Hi all,

I am planning to build my own deck out the back of my new house. I have some plans and some questions with the plans. 

My questions are:

1. What spacing do I need for my bearers, joists and stumps?

2. I only have 130mm clearance between concrete slab and doorway entrance. I am going to create a single layered structure that I saw on someone else’s post but am I able to use metal stirrups like this one and just dynabolt it to the ground and put the wood straight on the concrete?

3. Am I able to use 90x45 H4 treated pine for my structure? I can't use 140mm as it won't fit clearance.

Thank you!

 

[rwa1994]

Hey @Nailbag ,

Thanks so much for the pointers. I love these tips, I need all the help I can get! 😂

I do have a question, with the lawn section of the deck, I am going to dig it out a bit to ensure airflow, how should I treat it to prevent grass and weeds growing through the bottom of the deck?

thanks !!

[Nailbag]

Hi @rwa1994 and yes that would be the way to go. Laying down weed matting will then control regrowth once the boards are down.

Nailbag 

[rwa1994]

Hi @JacobZ , @Nailbag , @Dave-1 ,

Sorry to bother you guys again but I have a follow up question.

I have attached on the plans the area that will be concrete under and dirt. For the dirt section, where and how many holes do I need to pour the concrete into?

Sorry if this is a stupid question

Thanks heaps

[Dave-1]

Afternoon @rwa1994 

25 holes and concrete needed acording to thoswe plans. Note that the holes near the slab you may run into concrete foundation material so adjustments may need to be done. You wont know until you dig your holes next to the slab. I ran into the same issue when I was working next to my brick wall.

Dave

[rwa1994]

Hi @Dave-1 ,

thanks heaps. So I need a hole per stump over the grass section? 

thanks!

[EricL]

Hello @rwa1994 

It's great that you've received excellent advice from @Dave-1. Yes, you would need a hole per stump over the grass section. I strongly suggest using a builder's line and a level to make sure your stumps are lined up correctly. But please double check the location of your footing so that you get an accurate count on the number of footings you'll need. 

If you need further assistance, please let us know.

Eric

[rwa1994]

Hey @EricL and @Dave-1 ,

When using @JacobZ's render as attached, where would my noggins need to be spaced? I read on this post

that Adam said every 800mm, would that be the case for me?

Also, does anyone know what application Jacob used for his rendering?

Thanks!

[Nailbag]

I have to say I am unclear on the design plan @rwa1994. Ultimately what @Dave-1 has suggested being concrete/stump hole. However on my first impression of the layout there appears to be over-engineering here with 25 stumps for a total deck size of roughly 4.6m x 5.6m given 50% is over a concrete slab. Thats of course if my layout below is correct?

Joist should be at 450mm centres to the boards, but depending on the joist dimensions, your span between stumps once over the lawn can be far greater. Basically the same as the concrete anchor points in @JacobZ 3D render.

What are your dimensions for A, B, C & D?

Nailbag

 

[EricL]

Hello @rwa1994 

The more noggins of course the stiffer the frame, I suggest having a look at this discussion - Low-level composite deck over concrete and soil by @oninpena. This is an excellent example of noggins well spread out and offset to each other to provide maximum support and stiffness. Putting your noggins at 800mm is fine, but adding an extra one at the end wouldn't hurt either. Adding extra noggins does mean extra cost so I'll leave the decision up to you.  

The application Jacob used is called Sketchup.

If you need further assistance, please let us know.

Eric

[rwa1994]

Hey @Nailbag ,

I am also unsure of my design plan, that’s why I’m seeking clarification on here. I am only just starting out doing this kind of stuff. 

I have definitely made some errors like my over-engineering. 

My dimensions are:

A - 4667

B - 5580

C - 1547

D - 1860

I am clear from Jacob’s 3D render where the anchors need to go on the concrete slab but I am just confused about the grass portion. How does it connect into the ground and then onto the subframe of the deck? 

Again, I’m sorry for the annoying questions. I am just trying to learn and give it a go

Thanks