Decking Joist advice please

[metalsteve]

Hi,

I'm planning on building some raised decking approx 4.2m x 4.2m. It will be fixed to the house below the damp course approx 30cm above the patio and the far end will be fixed to posts concreted into the ground approx 40-50cm above ground as the garden tapers down hill slightly. My question is what size joists should i use and approx how far apart should they be spaced. The joists come in 4.8 m lengths in sizes 7x2, 6x2, 5x2 and 4x2.

Thanks in advance for any advice.

Steve

 

[ForestGrump]

I would say that 6 x 2 should be ok for that span, and around 500mm spacing but that depends on your decking pattern.

 

[big-all]

just make sure at the highest point off the natural ground level you are no more than 295mm to comply with the 300mm rule
in other words if your patio is laid onto the grass then you measure from under the slabs

 

[metalsteve]

thanks for your reply.

its basically gonna be straight parallel deckboards probably running parallel to the house, no fancy business.

big-all, so 300mm is the max allowed height of raised decking?

 

[metalsteve]

ah, a quick google answered that 300mm question, thank you so much big-all i wasnt aware of that rule.

 

[big-all]

providing the decking is below 300mm at the highest point it can be what ever height the natural contours take it
in other words it can be level with the highest point

you must also keep the decking/garden buildings and extensions below 50% off the garden area when built or after 1948 if later
interactive house is a brilliant help
http://www.planningportal.gov.uk/permission/house