decking structural calc?

[climber101]

Hi, see if I can tempt the structural engineers with this one Please..

For a decking project I am planning post and beam assy with 187x69mm single beams slotted onto 144x144mm posts and with 170x45mm joists across beams topped with 120x33mm deck boards.

I am understanding (don’t ask me to prove it! ) that from reading various sources that with above setup 1.8 is max between the posts supporting beams and 2.7m max between the beams which will support the 170x45 joists which are at right angles to the beams; with joists at a max of 400mm centres.

Current standards recommends that minimum a raised deck should be able to withstand is a “uniformly distributed load of 3.0 kN/m2 and concentrated load of 1.4 kN for the main deck platform and its support”

The question is can you tell me where I might find the calcs to see whether my proposed setup might meet this minimum standard as I’m thinking they might(?) not be that complicated that I might be able to follow them.

I fully understand and would be intending employ a structural engineer to provide the actual calcs and more if I go ahead but this is to reassure myself that what I’m currently pricing and sizing up might be in right ballpark.

Thanks in advance, cheers

[Shytalkz]

All well in. Where did you get the loading requirements from ooi?

The calculations *are* complicated btw

[climber101]

hi Shytalkz, thanks for responding

i got the loading statement from timber decking association code of practice TDA/RD 08/01 ('raised timber decks on new homes' - first edition november last year).

I noticed a few other companies that specialise in timber decking quoting the same loading reqts but as to where they originally came from don't know. Trying to work out if i'm pricing up the right materials and dimensions for build (I need planning permission because platform height is over 600mm from ground).

cheers

[^woody^]

Your proposed timber sections are way oversized for a deck. Why should a deck supporting a patio table , some chairs and a parosol need to equal a floor taking a load of dense timber furniture and other stuff? And 6" posts?

Deck companies use the b/regs guide for floor loadings because its there .... and they are lazy. A typical timber floor is designed for a combined load of about 200 kilograms per m2 (10 bags of sand every m2) - are you having elephants around for evening tea on the deck?

Generally for a deck you can use 50x100 for the main joists at 400 centres, with 50x150 for "purlins" as required, and 75mm or max 100mm posts.

Then use noggins to make it all nice and rigid and it wont defelect, move or creak at all

I think you need to re-look at the layout and design of the joists

There is a good chance of it sinking into the ground with all that timber