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Low-level deck building advice

rookabook
Budding Contributor

Low-level deck building advice

Hi Team

 

I am trying to put together a deck design and am after some guidance. I've read a bunch of these posts and hoping to tackle this project over the holdays.

 

See picture below showing the two areas that I want to end up looking a single seamless deck.

I will be using 140x19mm merbau decking and laying the boards parrallel to the sliding door with the BBQ infront.

 

A few questions I have:

 

AREA 1:

1. There is 190mm clearance from the soil to finish floor level. Would you recommend I use 140x45 H3 bearers and 90x45 joists (installed in line, not on top, with joist hangers)? This only leaves around 30mm clearance under the bearers. Is that enough?  

2. How many bearers will I need? How far apart? Is 450mm joist spacing ok?

3. I plan to dig holes and concrete in galvanised stirrups for footings. How many do I need/ how far apart? How deep do I need to dig?

4. Do I need to fix the frame to the brick walls? If so, do I just use dynabolts and space them out 10mm from the brick?

5. Where the frame meets Area 2 (tiled part) do I dynabolt it to the slab? Or just screw it in to the Area 2 frame?

 

AREA 2:

6. I'm concerned there is not enough clearance here to raise the frame up for drainage/ventilation. Using 70x45mm framing leaves no room for a gap and I dont want to have the frame touching the floor. Can I lay the framing on its side, giving me a 45mm frame height (and leaving a 25mm gap)? I planned to use either pedastools or galvanised L brackets here.

7. Would pulling up the tiles be a viable option to give more clearance? Or would getting all the adhesive off and leveled be a nightmare?

8. Since this is on a slab with tiles, do I only need joists running perpendicular to my decking boards, spaced every 450mm?

9. Whats the required spacing on the pedastools or L brackets?

 

Thank you in advance. You guys are a wealth of knowledge!

 

deck2.jpg

 

 

EricL
Bunnings Team Member
Bunnings Team Member

Re: Low-level deck building advice

Hello @rookabook

 

Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thank you for sharing your question about getting some low-level deck-building advice.

 

Before we dive into your questions, I suggest reading this excellent guide - How to build a low-level deck by @Adam_W. This guide will give you a general idea of how to plan your frame and what to take into consideration. Your observations for the deck over the cement are correct. Let me answer your questions about area 2.

 

  • Turning the timber frame on its side to have the 70mm facing up is possible. However, the strength of the 70x45 is when it's standing up. If you are building it in this manner, you'll have to install more footing to reduce the oscillation or sponginess of the deck frame. 
  • Removing the tiles is definitely an option. But, if you are removing the tiles, you might as well dig further to provide adequate ventilation for your frame and have the 70x45 timber facing in the right direction. I would recommend angle brackets as they will provide much sturdier support and will not move if anchored to the floor.
  • To answer your last two questions, you would need a plan. I suggest drawing a plan on pen and paper or your favorite drawing software. There are plenty of online deck calculators that you can try out to get an idea of how it's supposed to be laid out. You mentioned 450mm is the common gap between joists. This would be a good place to start. You can then decide in which direction the decking boards will be laid out.

 

  Area 1

 

  • The space of 30mm is not enough. I suggest Treated Pine Outdoor Timber Framing 90 x 45mm as an alternative to provide you with a larger gap at the bottom. Water drainage and air circulation are critical under the deck as trapped moisture will shorten the life of your deck. In open ground installations, we recommend using weed mat and gravel to be used under the deck. 
  • Again, to answer the remaining questions, I suggest drawing a plan. Have a good look at the low-level deck plans that other Workshop members have made.  

 

Once you've drawn up a preliminary plan, post it here for our members to see. We can then offer you advice and information about your deck framing. 

 

Please keep us updated with your progress,  we look forward to seeing your deck framing plans.

 

Here is a link for ideas and inspiration: Inspiring low-level deck builds

 

Here are some excellent discussions about low-level deck builds.

 

 

If you need further assistance, please let us know.

 

Eric

 

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rookabook
Budding Contributor

Re: Low-level deck building advice

Hi @EricL 

 

Thanks for the responses and links. I've put together the below plan based on:

 - Framing over the tiled area will use 70x45 TP with the 70mm face up. This will give a 25mm gap underneath the frame without removing tiles. Angle brackets will be spaced 750mm apart.

 - Framing over the soil will use 90x45 TP, built in 2 sections and screwed together. This will allow 80mm clearance from soil. Under this frame I will remove the grass, excavate a small amount, lay down weed mat and gravel.

 - All joists are 450mm apart

  

rookabook_0-1638239264366.png

 

Some questions:

Is number of footings and placement ok (1300mm apart)?

Do I need any near the brick walls or will the dynabolt fixings provide enough support?

Do I just screw the frames together where the tiled section meets the ground section (using the angle brackets near the edge of the tile as supports)?

Is the angled brackets spaced 750mm enough to account for the timber laying 70mm face up?

 

Thanks again.

 

EricL
Bunnings Team Member
Bunnings Team Member

Re: Low-level deck building advice

Hello @rookabook

 

Thank you so much for coming back to us with your plan. My apologies, I should've informed you earlier that before proceeding any further, I suggest checking with your local council on the rules and regulations regarding size and height restrictions on building low-level decks in your area. If not built to local council regulations you may be subject to a hefty penalty. 

 

I recommend looking at a span table for your state to give you an idea of where to place your footing. Because of the size and complexity of your deck, The current decking size you're proposing to build will possibly require a permit and your plans may need to be sighted and approved by the local inspector. I suggest engaging the services of a professional deck builder or a decking engineer to make sure your plans will pass inspection.

 

If you need further assistance, please let us know.

 

Eric

 

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rookabook
Budding Contributor

Re: Low-level deck building advice

Hi @EricL 

 

Thanks for getting back to me. I did speak to council who advised approval is not needed. The structure that is not over the slab complies with size requirements, distance from boundary and has a floor height under 1m. I've also had two builders quote the work who said the same.

 

The reason I am here is after seeing the quotes I thought I would tackle the project myself, with some advice from yourself/Bunnings team.

It's all the small details (footings, fixings, material sizes, etc) I want to confirm since the builders only gave a verbal plan.

 

EricL
Bunnings Team Member
Bunnings Team Member

Re: Low-level deck building advice

Hi @rookabook

 

I've consulted with my colleague concerning your 70 x 45 and we've concluded that it is not viable and will not hold up to the stress of being installed in that direction. I'm so sorry, but I'm changing my recommendation and suggest changing the direction of the timber and having it standing with the 45mm face up. You've mentioned that you would like to have a gap at the bottom of the timber. The only way to do this is to remove the tiles and chip away some of the cement until you get the clearance that you need. You could use a different medium such as steel. But you will have to look at a steel span table to determine which one to use.

 

In reference to your plan for the frame over open ground, if this is a single-layered structure you'll have to have 3 footings for every joist. Screws, nails, and joist hangers are not enough to hold a 2.6-meter piece of unsupported timber. You'll have to keep in mind that not only is the frame holding its weight, but the weight of the decking panels and people standing on it. This would be a good opportunity for you to have a look at Steel Floor Frame Custom Made. Combined with Ekodeck panels your deck will last a long time with very little upkeep. 

 

The advantages of having a steel frame are its fire resistance, corrosion, and termite resistance. It's compatible with any type of decking, Including composite, wood, tile & Hardwood. It's precut, planned, and comes in kit form for you to easily assemble. To get a free quote bring your proposed plan to the Special Orders desk of your local store and give them the details of your decking area. They will then send this to our provider who will then plan the decking frame for you. The quote is returned to the store and is then presented to you. You can also ask for a site-specific certification if needed.

 

If you need more advice or information, please let us know.

 

Eric

 

 

  

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rookabook
Budding Contributor

Re: Low-level deck building advice

Thanks @EricL 

 

Ok, I might attempt removing a tile or two to see how much effort is required and how much clearance I can gain.

 

I did look at those Steel-deck options but I dont have the clearance over the soil to put in a 185mm frame.

Similar to this link you provided earlier, I was planning to support the bearers (running horizontal in the plan) with the picutred footings.

The joists would be fixed with joist hangers and only ~1.2m length.

EricL
Bunnings Team Member
Bunnings Team Member

Re: Low-level deck building advice

Hi @rookabook

 

You'll notice that in @asifkhawaja's framing build. They used 140 x 45 and each section was doubled up creating an independent frame. This allowed them to put in 1-meter joist panels between the double bearers. You would need to use the same size of timber, framing technique, and create eight independent frames so that you can copy the footing pattern.

 

If you need further assistance, please let us know.

 

Eric

 

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rookabook
Budding Contributor

Re: Low-level deck building advice

Hi @EricL 

 

Could I still use 90x45 but go with double bearers like below?

 

rookabook_2-1638407074803.png

 

EricL
Bunnings Team Member
Bunnings Team Member

Re: Low-level deck building advice

Hello @rookabook

 

Thank you for the update on the plans for your decking frame. I'm afraid the 90 x 45 is not going to work as the wood is not strong enough and will possibly produce a bouncy deck. I suggest using the 140 x 45 as you originally planned. In reference to your new plan, I'm afraid you still need to increase the number of footings and lessen the distance between them. You'll also need to put footings near the Dynabolted ledger. As I've mentioned you'll have to copy @asifkhawaja's framing build.

 

If you need further assistance, please let us know.

 

Eric

 

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