How to get started on building a new deck over concrete?

[samdhoj1]

Hi Guys,

Need your expertise and guidance on selecting material and tools needed to build a new deck on a concrete floor. 

Have watched tons of videos and read a lot of articles on how to build a deck. 

Still confused on material and tools.

So your help and guidance will be much appreciated. 

Looking a doing a Merabu decking.

Thanks 

 

 

 

[StevieB]

Welcome @samdhoj1. We'd be happy to help.

Are there any specific questions you have about the materials and tools?

You mentioned that you've read a lot of articles already, but I just wanted to check that you've seen @Adam_W's guide How to build a low-level deck as it's a great place to start. You can also find out how others in the community have built their decks by checking out these Inspiring low-level deck builds. A list of tools and materials can be found in this Featured Project article: Low-level Merbau deck over concrete slab.

Our resident D.I.Y. expert @MitchellMc will be happy to help further with any questions you may have.

Look forward to seeing the progress of your deck.

Stevie

[MitchellMc]

Hi @samdhoj1,

I'm keen to hear of any questions you have and to assist with them. The first step is to determine your overall working height, governed by the distance between the concretes surface and the top of the doorsill. I can't quite work this measurement out from your picture if it's included. If you can let me know this height, I can start making recommendations on what supports and joists you can use.

Looking forward to your questions and that working height.

Mitchell

[Samdhoj]

Hi @MitchellMc ,

Thanks for the quick response. 

Sorry for not being clear on the Pic.

so the measurement is 3.87m X 4m X 0.18m height.

hope that makes sense. Thanks 

[MitchellMc]

@Samdhoj, 

Working with the 180mm overall height, you'll start by removing your 19mm decking. That leaves you with 161mm, and I'd suggest using Treated Pine Outdoor Timber Framing 90 x 45mm upon Builders Edge Pedestal Foot Bigfoot Xl 70 - 170mm. Alternatively, if you didn't want to use the feet, you could use Treated Pine Outdoor Timber Framing 140 x 45mm attached to the slab with Dunnings 50 x 100 x 50 x 5mm M12 Galvanised Angle Brackets. You'll Dynabolt these brackets down to the slab. You'll space your joists every 450mm across the span, orientated depending on which way you'd like the decking to lay. The decking lays perpendicular to the joists.

Tool wise, you'll need a cordless drill for fixing timber together, a hammer drill for putting holes in the concrete, and a circular saw for cutting timber to length.

Please let me know if you have any questions.

Mitchell

[Samdhoj]

Hi @MitchellMc ,

Thanks for the info.

Here are few question that i have :

1. How many Treated Pine timber do i need?

2. How many Galvanised Angle Bracket do i need?

3. How many Dyna Bolts do i need?

4. In some pic i did see Joist hanger do i need them?

5. Do i need screws to hold the joist or should i be using nail or both, if so how many and what kind and length ?

If you look at the pic why do some have double Timber frame in there and that wooden block but not on all sides?

Sorry to be a pain just trying to understand the reason behind.

Thanks

[MitchellMc]

Hi @Samdhoj,

Your joists will be laid every 450mm across the span. The number and length will depend on how you are laying them to suit the decking board direction. It's roughly nine with either orientation.

You'll need to place an angle bracket at least every meter along the joists. If you have nice joists at four meters, then that would be 36 brackets.

The amount of Dynabolts is the same as the number of angle brackets, which is 36.

You don't need joist hangers, but they are a convenient way to connect the joists to the frame and less hassle than drilling holes for brackets.

If you have a drill driver, it would be easier to use screws than nails. Zenith 14G x 85mm Galvanised Type 17 Batten Bugle Head Timber Screws would be suitable.

When a picture frame of decking is used to finish around your decking boards on the framed areas perpendicular to the decking boards, additional timber is needed to nail off both the decking board and the picture frame timber. Where the picture frame runs parallel with the decking boards, additional timber is not needed as it is nailed off the same way as the decking boards are.

Please let me know if you have further questions.

Mitchell

[Samdhoj]

Hi @MitchellMc ,

Thanks for the information, it's very helpful. 

Here is few of the stuff that im looking to doing on the decking, which will give you a clear pic and then you can guide me accordingly.

Based on the specrite calculator it has suggested me for around 32* approx 5.7m Merbau boards.

Also i would require around nine 140x45mm Timber Joist. 

Got few questions

1. what is the suggestive size length for the Timer Joist to order ?

2. Is the merbau requirement calc for around 32* approx 5.7m Merbau boards.correct ?

3. The above pic Timber Frame setting is basically used for Picture Frame decking right ?

4. The Hex screw to hold the all three Joints how long mm ones do you suggest. ? 

Thanks for ypu help.

[MitchellMc]

Hi @Samdhoj,

For the joists, you'll be looking for the first available length longer than the width of 3870mm. You'll need to check will your local Bunnings store to see what they stock. I suspect it will be 4.8m lengths.

The decking requirement of 32 x 5.7m lengths is correct according to my calculations.

Your picture does illustrate how to space the timber for a picture framed decking. I am unsure why they have the yellow spacer piece sitting on top of the "skinny bracket". It might be an exaggerated image, but this yellow spacer appears elevated above the other two blue pieces. This is not the case as the tops should be all flush.

For the three pieces of timber joined together, I'd recommend you screw the yellow spacer into the first blue piece of timber with Zenith 10 - 8 x 75mm Treated Pine Countersunk Head Screws. The second blue piece of timber can then be screwed into the yellow spacer with the same screws. Alternatively, you could do it with one Buildex 14-10 x 150mm Zinc Alloy Bugle Head Batten Timber Screw, but that might be a bit short to hold well. The next size up is Zenith 14 - 10 x 175mm Galvanised Type 17 Batten Bugle Head Timber Screws, but they'll be a bit long.

Please let me know if you have more questions.

Mitchell

[Samdhoj]

Hi @MitchellMc ,

Thanks for the reply does make sense now.

I do have few question regarding the screws that are required.

A . For screwing the Joints to the concrete you have suggested using Dunnings 50 x 100 x 50 x 5mm M12 Galvanised Angle Bracket where M12 is basically the size of the hole, where the single hole is where the Dyna bolt will be fitted and the double holes is where the Joist will be screwed. My question is 

A.1 what size Dyna bolt to be used for fixing the Angle Bracket to the concrete, Will Ramset 12 x 60mm Galvanised be good enough or do i need more longer 70mm or longer ?

A.2 What size screws to be used for fixing the Angle Bracket to the Joist? Joist size 140x45mm 

B. For screwing the Merbau 90x19mm board to the Joist i see that you have recoommended Zenith 14G x 85mm Galvanised Type 17 Batten Bugle Head Timber Screws - 25 Pack.

B.1 What difference does it make by using 8-10, 10-8, 8G,10G,12G,14G Type 17 Decking screws, is the Head size of the Screw?

B.2 What effect will it have by using smaller G or Larger G or 8-10 or 10-8 Type 17 screws?

Wait for your reply.

Thanks