How to build low-level decking over concrete slab?

[Sujoy]

Hi All, 

Newbie here and started doing small DIY stuff like making merbau planter boxes :). Now I am planning to start my decking and found this forum extremely helpful gaining the basic knowledge about decking, especially guidance from @MitchellMc in similarly low level decking threads. Here is my project details (please refer the photo attached -

• Total area - 6.3mx4m 
• Clearence at Point#A:140mm, house slab sloping towards Point#B:150mm and then concrete apron sloping another 40mm, so total clearance at C is 190mm. 
• Joists will be as shown in the photo and bearers just connecting end of the joists at A and C. 
• Will attach the bearer to brick wall A with 10mm gap (using shims) and planning to joist hanger and L-brackets to hold the joists. 
• Have granite pebbles in D, planning to use pavers + EcoDeck Bigfoot in that area to hold the joists. 
• Will be using 90x45mm H3 pine for bearer and joists and 140x19mm merbau, so total height for joist + merbau is 109mm. 

Questions: 

1. Ground clearance in A is 31mm (140 - 109), B is 41mm (150-109) and C is 81mm (190-109). Based on this, is L-bracket a good option? If yes which L-bracket should I choose? 

2. With L-backets, I probably have to use shims underneath the joists, isn't 81mm too high for using shims? what are the other options I got? Looking for options other than EcoDek foot (planning only to use it in the pebbles area D). 

3. Need help with detail specs of dynabolts, L-brackets etc. suitable for the above project. 

Many thanks :). 

[Dave-1]

Morning @Sujoy 

Those concrete anchors are a little long The deck is only low and wont have a lot of movement so id go with something shorter. either a 50mm or a 60mm anchor Ramset 8 x 60mm Galvanised AnkaScrew Masonry Anchor (box 10)  Id be wanting 50mm into the concrete type deal.

With your bearer turned sideways I am not so keen. I know the span is short but my head baulks at the flex. How about taller styled right angled brackets and do away with the bearer entirely? Dunnings 60 x 100 x 35mm M10 Galvanised Angle Bracket 

You can still attach the skirt to the ends of the joists. In reality you could use the bearer or the right angle. Im trying to think of a reason other then personal preference

Dave

[MitchellMc]

What you're doing looks fine @Sujoy. As @Dave-1 mentioned, it is best to have the bearer in the upright configuration, though as long as you support it readily, there shouldn't be too much flex.

There's no particular need to coat the underside of the bearer with bitumen, as they are treated for above-ground use. However, if it comes in contact with the ground or is very close to it, you might like to.

Those screws look fine. I suspect you need the length to go through the bearer, the air gap and then into the concrete. Just ensure at least 30/40mm is screwed into the concrete.

Mitchell

[Sujoy]

@MitchellMc @Dave-1 Thanks, I had no option but to turn the bearer sideways as total clearance was only 80mm. I first fixed the packers under the bearer and drilled 8mm hole through the gap between the packers and then screwed using the 8mm galavanised Masonry Ankascrew  into the concrete. The screws are every 450mm, and has gone 45mm into the concrete making it very sturdy. Also added joist tape to avoid moisture accumulation on the top. Attached photo for reference, hope this is fine? The overall levelling seems to be alright, progressing well 😊. 

Another question re the screw for attaching angle brackets to joists, is the screw shown in the 3rd photo ok to proceed with? 

 

  

[MitchellMc]

That's looking good @Sujoy. The screw you've pictured is suitable for attaching the brackets to the joists.

Mitchell

[Dave-1]

Morning @Sujoy 

My preference is a bolt But yeah that screw should work.

(I like bolts as I always feel there is less chance of splitting and an overall stronger connection between pieces)

I know you probarly have but a pilot hole would be wise.

Dave

[Sujoy]

@MitchellMc @Dave-1 I am almost done with the decking, coming along nicely and very happy with it. Thanks to you guys for all your guidance 🙂. 
there is a bit of glitch though at the end while laying the last merbau, I have only 60mm remaining but need to lay another 140mm as shown in the picture. 

Can I add one more 90x45 bearer screwed to the first bearer? So that gives me 60mm + 45mm=105mm, 1 merbau fascia 19mm totalling to 124mm, this gives 21mm overhang for the last sheet. 
I need some help to make that 45mm extension sturdy. 

[Dave-1]

Evening @Sujoy 

The deck is looking sweet as! Love that term as it really encompasses so many things!

The deck is looking very professional.

Your solution is bang on what I would do to extend it that tiny bit more. Id paint it black before attaching so its super tidy.

Now here is a question for you...

Do you think you would have figured out how to impliment the "fix" if you didnt have the experience of building the deck?  

You now have a huge amount of knowledge that you have learnt yourself!

Dave

[JacobZ]

Hi @Sujoy,

That deck is looking fantastic, nice work!

As @Dave-1 has said, adding that extra 90x45 is a perfect solution to your problem and will give you a nice little overhang that will look fantastic.

I'd suggest grabbing some ZENITH 14G - 8 x 75mm Class 3 Galvanised Bugle Batten Screws and using one every 600mm or so. This will give a nice sturdy connection between the new timber and the existing bearer.

Let me know if you've got any further questions.

I can't wait to see everything once it's finished.

Jacob