How to build a small deck using modular decking kit and adjustable supports?

[martyjames]

After further research and helpful input from you guys i am now planning to build an approximately 3m x 3m deck (no pergola) over a slightly sloping concrete slab in my backyard (pic attached).

I am a very basic diyer so want simple and easy to understand but want the deck structurally sound and long lasting.

I found Bunnings sell Modular Decking Base Frame kits like https://www.bunnings.com.au/1144-x-1144mm-modular-decking-70-x-45mm-ekodeck-base-frame-flat-packed_p... etc

I am thinking to use 9 of these kits 1144mm x 1144mm to get a base roughly 3.5m square.

I will use the Modular decking support feet to level the frame : https://www.bunnings.com.au/50mm-modular-decking-adjustable-support-foot_p8451224

I watcheds this video from Bunnings on how to put it all together: https://www.youtube.com/watch?v=1tjQdmsmkP8

Over the to of the frame i will install composite decking

Quesions

1.The video does NOT show the frame being attached to the ground at all - does it need to be? If so how would i attached it to the concrete slab? ( i can easly attach to the low wall at back of yard - is that ok?)

2.Can you send me a link to the correct "battern" screws refered to in video

3. How would i work out which length of Modular decking support feet to buy? They come in 50/100/150mm lengths from your website

4. Is the Modular Decking Base Frame kit timber 100 percent weather proof and does not require any finish?

5. I am thinking i need a very long spirit level to ensure frame is level - can you please provide a link to suitable level

6. Can you send me a link for suitabe screws to screw the frames together if different from "battern" screws in no.2 above

Is there anything else i need to take into account or buy?

Thanks in advance

Martin

[JacobZ]

Hi @martyjames,

I'll try to answer your questions in an order that will make sense during installation.

Working out which length support feet to buy would require a level. Over the distance you are proposing, a laser level would be the best option, but may be cost prohibitive. A set including a long level and a shorter level such as Stanley FatMax 2m And 600mm Spirit Level Combo should be adequate for your project.

Start by putting a mark (datum point) at the desired finish height on the high side, taking into account the pedestal foot, thickness of the deck frame and the thickness of your decking boards. Using 70mm thickness of frame and 23mm for the thickness of the composite decking board as an example, then adding room for the pedestal foot, I would suggest this mark should be no lower than 130mm above the slab. Once this datum point is set, you can use the laser level, or long level to mark a line at this height across the roughly 3.5m to the other side of the deck. This will allow you to once again measure down from your line and calculate which pedestal feet you will require. Please note that at higher heights, Good Times Co. require steel supports such as 140mm Modular Decking Support Steel for added strength and stability.

You might want to have a look at Good Times Co. - Decking Planner as well as the assembly instructions during the planning stage.

All of the modular decking kits from Good Times Co. are made from H3 treated pine, which is suitable for use outdoors but not in direct contact with the ground or fresh water. This level of treatment provides protection against decay and insect attack, making it suitable for applications such as outdoor decking, fencing, pergolas, and other outdoor structures where the wood may be exposed to weather.

While not specifically advised in their installation instructions, I would suggest attaching the frame to the ground is certainly worthwhile. The weight of the structure should do a lot to keep it in place, but I would be far more comfortable knowing that it is mechanically secured. This could be achieved on the concrete slab using something like Pryda Post Anchor Bolt Down Heavy Duty 90mm M12 suitably attached with masonry anchors to the concrete and batten screws to the frame. It would also help to fix it into the low wall as you've described.

The advised batten screws are ZENITH 14G - 8 x 75mm Class 3 Galvanised Bugle Batten Screws or a suitably galvanised screw of the same size.

I hope this helps to clear things up a bit. If you need more advice or any clarification, please don't hesitate to ask as I'm excited to see your project progress.

Jacob

[martyjames]

Thanks for the detailed reply Jacob, much appreciated Could you send me a link for suitabe screws to screw the frames together please. 

Would this ozito laser level be suitable? https://www.bunnings.com.au/ozito-5m-laser-level_p5660756

Thanks again

Martin

[JacobZ]

Hi @martyjames,

The batten screws I have linked to are also suitable for the purpose of screwing the frames together. There's no need for a different kind of screw for this.

This laser level would be suitable, assuming you are careful to get it perfectly level before transferring your mark, but it may be difficult to see the line outside in natural light. Green line laser levels tend to be better for outdoor use, but they tend to be more expensive. I would probably advise just using the spirit level and tracing the line to its full extent, then moving the level across, finding level from the original line and tracing across. The spirit levels will be far more useful across the full extent of your project.

Let me know if there's anything else.

Jacob

[martyjames]

Many thanks Jacob, i'll follow your recommendations.

Do you also recommend that i use this tape on the top surface of the base frame where it contacts the composite decking?

https://www.bunnings.com.au/cagroup-50mm-x-20m-bearer-protector-g-tape_p0224655

(i read it should be used under composite decking?)

Cheers

[JacobZ]

Hi @martyjames,

I would definitely recommend the addition of joist tape to the top of the frame as this will stop any water pooling on top of the joists finding its way into the timber. While H3 pine is suitable for outdoor use and exposure to weather, if water is allowed to sit on it for long periods of time, it will still have negative effects.

Let me know if you have any other questions.

Jacob

[martyjames]

Thanks Jacob, I'll definitely use the joist tape. Since the last post i purchased 9 of the modular decking kits and assembled them - pic attached. I had to cut one down to fit the available space but it shouldnt be a problem.

I have to say i am disappointed with the quality of the timber - see pics attached. Parts of timber missing, holes where knots have fallen out etc. Too much effort to return. Will the structural integrity be ok do you think? Anyway, thanks for all your information so far.

[martyjames]

Hi Jacob

I assembled the frame and used the recommended adjustable feet. In the Bunnings  video the guy places pavers under the supports to boost them up. I only had bricks (brand new) so used them. Should i cement them onto the concrete slab or is free standing ok (per the video)?

Many thanks

[MitchellMc]

Hi @martyjames,

I'm sorry to hear that some of the timber had knots and damage. I'll pass this feedback on to the supplier. However, I can assure you that the timber still meets the structural rating of MGP-10 and is perfectly adequate for your deck. The knots, although unsightly, do not pose any significant implications for your project.

If you did want to return them, I'd be more than happy to facilitate.

Bricks don't have as large a surface area as pavers, so it might be an idea to place cement around them to increase their mass. But it sounds like it could be a simpler approach to replace them with pavers.

Please let me know if you have any questions.

Mitchell

[martyjames]

Thanks for the reply Mitchell. I replaced the bricks with pavers (all but one, need to buy 2 more!) and have bolted the deck to the slab using 12 mm  Zinc AnkaScrew Masonry Anchor and 6mm thick galvanised angle brackets - its now rock soliid on the slab. I applied the CA Group joist tape as you guys recommended. The frame is level and just about ready for the composite decking. Anything else i need to take into account?

I also built a brick planter box per Bunning video https://www.youtube.com/watch?v=3QXHF9YTelM . Per the video he says to apply bitumen paint to the inside of the box. Can this be painted over at the top of the planter where it may be visible (just above the soil line)?

Thanks again