Low level deck in alfresco on existing concrete slab

[fahad1308]

Hi,

I wanted to build a wooden deck in Alfresco on existing concrete slab to sit flush is bricks. Size of the deck is 4090mm x 2600mm. Here are few questions:

• I've to maximum height of 90mm to play around (refer attached picture). Is it even possible? My understanding is 19mm is deck boards and rest is 71mm. And there has to be at least 10mm air flow space under the deck(joists resting on galvanized brackets), that leaves me with 61mm. Can you please suggest/recommend what type/size of joists to be used?
• Is merbau only decking board available or are there any other types to choose from? Will the other ones vary in size?
• I wanted to deck it without visible screws on deck, is that possible?
• Is there a checklist that can help me in purchasing all the required materials for this project?

I've referred some great posts and tutorials in this forum but all of them are with height > 100 mm.

[EricL]

Hello @fahad1308

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

I suggest having a look at this guide - How to build a low-level deck by @Adam_W. This will give you a good idea of how to plan your deck. If you were to use 70 x 45 plus a composite decking which is 23mm thick you would have a total of 93mm with no gap. If we lift the frame by 10mm you would have a total height of 103mm. That would take you 13mm past the brick line. Would it be a trip hazard? Yes, but you can also build the deck with the panels very close to the sliding door frame to make it less of a hazard. You'll have to test it with a decking plank to find out.

Is there a choice when it comes to decking panels? There is hardwood, treated pine, and composite decking. Both types can be attached to the decking frame with hidden fixtures such as Camo Marksman System for timber and Ekodeck Concealed Kit for composite decking.

Your plan will actually dictate the list. I suggest getting pen and paper and drawing up a rough plan of your deck frame. Are there areas that go lower than the brick line of 90mm? If there is would it be more practical to split the deck so that you can use bigger timber for the frame? 

Have a look at these amazing low-level decks that our Workshop members have shared.

• Low-level composite deck by @oninpena

• Low-level deck over concrete by @Backyardtradie

• Low-level Merbau deck over concrete   @DIYImpressions  

If you have any other questions we can help with, please let us know.

Eric

[fahad1308]

Hi @EricL,

Thanks for response and sharing blog posts, very informative. 

I've decided to stick with timber merbau decking. 10mm space + 70mm frame + 19mm deck board = 99 mm (this will be 9mm above brick line, I'll get a plank and test it out soon)

I don't have any areas going lower than brick line, I've put together rough image frame and end deck, refer below:

• First two and last two joists were spanned at 70mm for picture framing
• 70 x 45 joists with a span of 450mm

Do you recommend any changes to frame/structure?

Materials: 

• From the blog post by I've understood that timber used for framing must be H3 treated, can I use this:70 x 35mm L/M Outdoor Framing MGP10 H3 Treated Pine - Bunnings Australia or  70 x 45mm L/M Outdoor Framing MGP10 H3 Treated Pine - Bunnings Australia ?

Thanks,

Fahad

[StevieB]

Hi @fahad1308,

@MitchellMc and @EricL will be happy to help with your deck project when they're back on the site tomorrow. Let me tag @Adam_W in the meantime to see if he can share his thoughts.

Stevie

[MitchellMc]

Hi @fahad1308,

That's a great plan you've put together there, and everything looks quite substantial. I'd suggest going with the 70 x 45mm L/M Outdoor Framing MGP10 H3 Treated Pine as the 70mm timber is already slightly undersized. The additional thickness will benefit the overall rigidity of the deck's structure.

Keep the questions coming. We're here to help.

Mitchell

[EricL]

Hello @fahad1308 

It looks like you have everything planned out. It's great that you've received excellent advice from my colleague @MitchellMc. I look forward to seeing your decking frame take shape.

If you have any other questions we can help with, please don't hesitate to post them.

Eric

[fahad1308]

Thanks @MitchellMc!

I'm putting together list of materials that I'll need.

I want to build a deck using hardwood, referring to most of the posts shared earlier, merbau seems to be most commonly used, is that the one you would recommend? How do I decide on what size(including length) of the boards that I can buy?

Regards,

Fahad

[MitchellMc]

Hi @fahad1308,

Merbau decking is exceptionally popular as it is not only hard-wearing but cost-effective. However, we also offer a range of other hardwood decking, including Stringybark, Spotted gum, Ironbark, Tallowwood, Karri, and Forest reds. Check out @Adam_W's article on How to select decking timber. I've recently built a Merbau deck and have been very happy with the timber. 

Regarding what size you'll need to buy, that will depend on how you are laying it and if you want continuous lengths across the deck. If you do, you'll be looking to purchase lengths slightly over 4090 or 2600mm. The width of the board is really a personal choice. A wider board has more presence and can look more impressive.

I'd suggest contacting your local store to see what sizes of hardwood decking they have in stock for your project.

Mitchell