Building a low-level deck over concrete

[DIYImpressions]

Preview of the finished resultHello Team, i plan to build a deck outside within the shed area over concrete area.

Dimensions are 8 meters x 3 meters. Ground clearance at the entrance  (left side) is 120mm but on the right side window clearance is 170mm.

I want to build a deck with merbau 140mm running to parallel to house with picture frame design. 

 

 

 

 

 

Also i want to lay pebbles at the edge of decking like this

I have read the “Building low clearance guide” and want advice on lengths required to start the project. Appreciate your guidance. Thanks

[MitchellMc]

Hi @DIYImpressions,

I'm keen to assist with your project. Have you started drawing yourself up a plan of how you'll build the structure? What sort of advice were you looking for on lengths?

Here are some renderings I've put together on a possible way to build your deck. It's something I've been working on for a while and it's based on a system where each square meter of the deck is treated as its own repeatable entity. There are only nine separate tiles used to build a decks structure. I've drawn your 8000 x 3000mm deck to scale using 90 x 45 outdoor framing timber. In the first image below are the 1000 x 1000mm tiles I've used. This might all be a bit boring, but it's an interesting concept to me.

Let me know what you think and if this makes it easier for you to understand how the deck will be constructed. Feel free to ask any questions. We're here to help.

Mitchell

[DIYImpressions]

@MitchellMc 

Thank you. I have read that in detail and also look at other low-level decks post. I have few more questions before I place the order

1) There are two joists together on left and right. Why is that? and what's in between them and how they are attached?

2) How much gap should I leave between two Merbau decks? Also, I see one of the Merbau plank is stripped (the top plank). Can it be done through bunnings?

3) With 120mm ground clearance, the total deck length will be 109mm (19mm + 90mm). This means 11mm will be the gap between the slab and the bottom of the joist/bearer. Can I cover the gap from the sides to prevent rodents from going inside?

4) How to maintain the 11m clearance throughout while screwing the timber? 

5) Joist lengths will be 210mm? and can I get these exact cuttings from bunnings?

6) How to calculate qty required for timber and merbau? and what sort of angle brackets, screws etc I should be looking at.

Thanks

NR

[EricL]

Hello @DIYImpressions 

My colleague @MitchellMc will be back on Friday. Let me try and answer some of your decking questions.

• The two joists that are close to each other and are separated by an offcut piece of timber is a technique used when you are picture framing your decking panels. Picture framing is laying an outside border around your decking panels. In this manner, none of the ends of the decking panels will be exposed to viewing giving it a very professional finished look.
• The most common gap used is 3mm between decking panels. The maximum length the store saws can strip cut is 2.2 meters due to space limitations. If your panels are longer than that, you'll have to use a circular saw to strip cut your panels.
• Technically yes, you can cover the 11mm gap. But it would be ideal to leave the gap so that you get airflow running under the deck.  
• To maintain the gap between your floor and the timber frame, I recommend using Macsim Fasteners 75mm Assorted Window Packers - 90 Pack.
• Yes, you can have your joists cut to the length you require. I suggest visiting your local store so that you can arrange for the cutting service.
• The quantity of timber framing is based on the plan that you've drawn up and the size of timber you've chosen. By speaking to one of the senior timber specialists in the timber yard, they will be able to advise you what timber is in stock and which length will be the most economical for your build. 
• The Merbau decking panels will also be calculated based on your plan. Here's a link to a handy deck calculator you can use to estimate your needs: SpecRite Deck Calculator.
• For your angle brackets, I suggest using Dunnings 40 x 80 x 40 x 5mm M12 Galvanised Angle Bracket and progressing to Dunnings 50 x 100 x 50 x 5mm M12 Galvanised Angle Bracket by the time you reach the area with a bigger gap.
• I recommend using Zenith M12 x 65mm Hot Dipped Galvanised Cup Head Bolts And Nuts - 12 Pack in combination with Zenith M12 Hot Dipped Galvanised Washer. To mount the bracket to the concrete floor, I suggest using Dynabolts for the interior of the deck and Ankascrews for the outside perimeter to prevent cracking the cement base.
• To screw your joists together I recommend Zenith 14G x 100mm Galvanised Type 17 Batten Bugle Head Timber Screws - 25 Pack.

Let me tag @MitchellMc in case he has more information to add to the recommendations I've given.

If you need further assistance, please let us know.

Eric

[MitchellMc]

Hi @DIYImpressions,

It appears @EricL has comprehensively answered your questions.

Our team in-store can't cut that last Merbau decking board down to size for you. Our saws don't have the ability to rip a piece of timber down the middle like that. You'll need to use a circular saw at home to do it.

Please let us know if you have further questions and keep us updated on your project.

Mitchell

[DIYImpressions]

Than you @MitchellMc @EricL 

I will be visiting bunnings to place the order. Few more questions

1- I am seeing double joist on the left and right corners and assuming this is because I want to have a picture frame design. How much is the interval between the joists? 

2- Do I need top and bottom horizontal joist? I have seen couple of projects where joists weren't used horizontally. 

3- At what interval I should screw the deck panels? I really want screws to be invisible. What can be done here?

4- @EricL on your comment in using "Dynabolts for the interior of the deck and Ankascrews for the outside perimeter to prevent cracking the cement base" can you please link the required product.

5- I am also bit concerned on mounting the bracket on concrete and on joist. How do I start? Is there a technique to follow such as to screw down the bracket first on concrete and the mount the joist?

Thank you so much.

[EricL]

Hello @DIYImpressions

Let me answer some of your questions.

• If you're asking where the timber spacers are located on the joist frame on a picture framed deck. It depends on the width of the picture frame side. If for example, it is 3 meters wide, I recommend putting a timber spacer every one meter and a mounting piece at the start and at the end.
• If your joists are sufficiently supported by the angle brackets you can sometimes forego the horizontal pieces. The horizontal pieces are placed in to prevent your timber joists from twisting.
• If you wish to have that clean no screw look, I suggest using the Ekodeck Quickfix Concealed Kit.
• I recommend using Ramset 12 x 60mm Galvanised DynaBolt Plus Hex Nut Bolt for the interior and Ramset 12 x 75mm Galvanised AnkaScrew Masonry Anchor - 10 Pack for the outside perimeter.
• My only tip for the installation of the angle brackets is to keep nuts loose so that you can uniformly adjust the level of the joist. Once adjusted, you can then slowly tighten the nuts to keep the level you've set it at.

I'm sure @MitchellMc will add more information in case I've missed anything.

If you need further assistance, please let us know.

Eric

[DIYImpressions]

Thanks @EricL 

isn't ekodeck quick fix kit is used for composite deck? In my case i am using Merbau deck. Also after how much space should I screw the merbau deck panels? 

Regards 

[MitchellMc]

You are correct @DIYImpressions; the Ekodeck Quickfix Concealed Kit is designed for use on Ekodeck decking. I'm not sure whether that kit works with Merbau decking, but I do know you can use a Camo Marksman Pro 133mm-146mm Wide Board and Camo 7G x 48mm Edge ProTech Coated Carbon Steel Trimhead Deck Screws to conceal your screws.

When you ask, "how much space should I screw the merbau deck panels?" do you mean how much gap do you leave between the decking boards? If so, between three and five millimetres, but the Camo Marksman Pro creates an automatic 4.7mm spacing whilst using it.

Mitchell

[DIYImpressions]

Hi @MitchellMc 

i meant how many screws I should mount on Merbau deck and after what interval: see yellow circle in this pic for reference

what brackets i should be attaching to mount horizontal joist to vertical joist like below so that front side of horizontal joist is plain without any nuts and make it easy to mount merbau panels on side

and in few of the projects i have seen black spray on top of joist and green on sides of joist. What is that and do i need it in my case?

 

thanks