Decking over concrete slab

[Tracey113]

Hi

we are looking to deck our alfresco area, its a concrete slab with a 70mm step down - not much I know, what’s the best way to go about it with such a small step down to work with ? 

does anyone also have a great program to work out deck plan / spacing etc ?

thanks heaps!

[asarson]

Hey mate, 

I cant remember precisely the width is about 4500 I think I put them at around 800, I just used blue plugs and batten screws to hold in place. Since the weight of the deck itself and no upward forces I went easy on the fixings to the concrete. I have since made some additions for those who are interested. 

Simple cantilever to support BBQ & stone benchtop, plywood flooring, cabinetry to come shortly. 

Cantilever deck extension for built in BBQCantilever deck extension for built in BBQ

-Andrew

[Jason]

Looking fantastic Andrew (@asarson)

When you have a minute it would be good if you could Start your own new discussion and share your project. It deserves its own thread! I'm sure members would be really inspired by what you have done.

Thanks,

Jason

[holmess]

Hey could anyone tell me what the black material is on the top of the joists in the photos of this deck? I'm doing the same board over and alfresco area and am worried about cupping. Any ideas to prevent this? 

[asarson]

The black material on the joists is just black paint, this is so that the joists cannot be seen through the decking spaces. Given you have sufficient gap between the concrete and decking with wide enough gaps between boards you shouldn't have a problem, we gapped ours at 5mm and the deck sits barely 45mm off the concrete. We also screwed in wider spacing the screws 30mm and 110mm on 140mm boards. 

Just a photo update on the threat - BBQ complete. 

[Jason]

The barbecue looks fantastic @asarson. Well done. I imagine you'll be spending a lot of time out there with friends and family as the weather warms up. 

Jason

[holmess]

Cheers mate for the advice,

Your deck is mint 👌 and thanks again for the advice about the spacing. 

How did you secure the joists to the brickwork? Last time I decked I used masonry anchors but I found that took a long time. Did you just screw straight to the brickwork with blue spaghetti?

What was the time frame to complwte the initial deck?

[asarson]

We just drilled into the concrete and like you said, blue plugs and used batten screws to hold it down. We didn't go nuts screwing it down to the concrete since there was a lot of weight in the deck holding it down and no upwards forces. Probably about a day setting out to get to screwing down boards. 

[Jason]

Great to see you getting fantastic advice @holmess. Welcome to Workshop. We're looking forward to seeing your own projects soon. Feel free to post anytime you need a hand or have something to share. 

Jason