How to build a deck over my exposed slab?

[dgialanze]

Hi There. 

I'm wanting to get started on an outdoor deck in my backyard. I'm just after advice on where to start and what i would need.

I have attached a photo below to show an example on measurements and where I would like the deck to go. 

I would need a subframe below first i believe and I'm contemplating going Eko Deck as I've been told positive things about it. 

The Red line is the overall space I want the deck to go to. 5.310m X 3.850m

The Blue line is the points to existing pillar.

The White line is the height. 0.135m

Thank you!

 

[JacobZ]

Hi @dgialanze,

A warm welcome to the Bunnings Workshop community and thank you for your post.

A good place to start is with the following video and articles:

• How to build a deck
   
• How to build a low-level deck
   
• How To Build A Deck
   
• How to understand deck components
   
• How to understand deck span tables

They should help you understand the basics.

With your space, I'd suggest using 90x45 timber for your frame. As Ekodeck is 23mm thick and your frame is 90mm thick, you'll then have 22mm beneath the frame which is not a lot of room. Being so close to the ground, your deck is at increased risk of rot as moisture can build up underneath the deck. With limited airflow, the moisture will not dry out as well as it would with more room for airflow.

In the past, we have often recommended H3 Pine as a material for constructing low-level decks, however, new products are coming to the market that are better suited to this purpose. These 90 x 45mm 4.8m MGP10 H4 Treated Outdoor Structural Radiata Pine are currently a Special-Order item, so you would need to place an order for them, but they are the best product for this purpose. They are H4-treated, meaning they can be used in direct contact with the ground. This means they will last much longer in this application.

With this height, your options for supporting the timber are very limited. If you were happy having a very slight 3mm step up, you could use these Builders Edge 25-40mm Minifoot Pedestal Feet to support the frame. If you don't want to have a step up, you would need to support the timber with packers. There's nothing wrong with this, but I'd only suggest it as a last resort.

If you can let me know which way you want your decking boards to run in relation to the door, I'd be happy to help you with a basic design for your frame.

Let me know what you think, I'm happy to provide further guidance if required.

Jacob

[dgialanze]

Hi  Jacob!

Thanks for the quick reply.

 With the frame going to be 90mm thick, I would have 45mm to play with. If you don't recommend Ekodeck would you have an alternative suggestion for the decking boards?

For the frame, what would you suggest in terms of securing the frame to the concrete?

The decking boards i believe we would go vertically.

Thank you!

[JacobZ]

Hi @dgialanze,

Hardwood decking such as this 90 x 19mm Merbau Decking will give you an extra 4mm of height to work with which makes the Builders Edge 25-40mm Minifoot Pedestal Feet a viable option while still having the decking flush with the top of the brick step. You shouldn't completely rule out Ekodeck as it is a great product and is still a viable option, but the very slight difference in thickness would mean your only option for supporting the deck is packers.

Regardless of the vertical support you use, whether it is pedestal feet or packers, you can use galvanised angle brackets with masonry anchors to attach the framing to the concrete beneath. These Dunnings 60 x 60 x 35mm M10 Galvanised Angle Bracket are a good option that can be attached to the deck frame with batten screws and to the concrete with DynaBolts or AnkaScrews.

For your decking to run perpendicular to the door, your frame would need to be built to suit. Please see the below render of a basic frame that will allow you to run decking boards perpendicular to your door.

You might like to have a quick look at How to build low-level decking over concrete slab? from @Sujoy. Their project which is reaching its final stages currently is very similar to yours.

Let me know what you think and if you have further questions, please don't hesitate to ask.

Jacob