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Decking Frame Over Concrete Patio Help Needed

Postby dt_diy » Thu Aug 25, 2016 2:51 pm

Hi guys,
DIYer here looking to build my first deck and desperately need some advice!....

I have a concrete patio that I want to deck over.
The problem is, the concrete, while sound and stable, is only 135mm below the patio door sill, so I don't have enough room to use 6x2 joists.
I thought I could use 4x2 joists (actually 97mm x 45mm) and 28mm deck boards and pack the joists up off the concrete 10mm to allow water to drain.
I'd fasten the joists to the concrete using either 7.5 x 150mm concrete screws going straight through the joist, or attaching some angle brackets to each side of the joist and screwing to the floor that way.
Is this a good idea? Call me lazy, but I really don't fancy ripping up the patio so I can use 6x2s :)

If using 4x2s in this situation is ok, how often would I need to pack the joist up to prevent bowing and bouncing? Every 300mm or can I get away with wider gaps?

Thnaks for your help
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Simply Build It

Postby welsh brickie » Fri Aug 26, 2016 7:39 pm

you can place them at 400mm centres
welsh brickie
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