Deck Frame Design

[C0ffin D0dger]

I'm putting a composite deck on the back of my house to come up level with some bi-fold doors and I'm after a sanity check on the design for the framework. All comments welcome!

Deck roughly 30m2, 10m x 3m.

The composite boards suggest a joist spacing of 30 cm. Boards running parallel to the house.

I know the convention is to use 6x2 for the framework but I don't have much height to play with without a lot of excavation that I'd like to avoid so I want to use 4x2. More posts, noggins etc. specified accordingly.

Will be using 4 inch / 10 cm posts concreted in to support. Max height off ground is no more than about 20cm anywhere.

Picture says a thousand words and all that, knocked up with Powerpoint, not to scale, and there aren't enough joists shown if anyone wants to be clever about it The red bits are where I'm proposing to put the posts.



Does it look okay in terms of support? Want it to be solid. Intend to fit noggins between each joist for extra rigidity. As mentioned it backs onto the house so will be using a ledger board to support some of the joists bolted onto the brickwork with a suitable drainage gap.

Thanks

[option click]

I built something more or less the same size a few years ago, although my middle supports rested directly on an old patio.
Supports look fine - in fact I used fewer and mine hasn't shifted an inch.

I sunk concrete fence posts into the ground and bolted bearers to them - it adds time but it means you don't have any timber in the ground so it should all last longer.

Edited by option click on Friday 31st August 16:15

Edited by option click on Friday 31st August 16:16

[Ian Geary]

I used some of these to hold up a deck

http://www.chilterntimber.co.uk/product/decking-co...

They were about £8 each from the supplier I used but hold a 4x2 nicely and zero worry about rot.

[anonymous-user]

Please make sure you use the correct timber for the joists. All too commonly I see nice decks built using Use Class 2 treated timber (I.e. standard treated carcassing and joists). This is NOT suitable for decking. All timber substructure components including posts AND joists should be Use Class 4 treated!

UC2 treated joists will last about 5 to 7 years before decaying badly at the junction between the deck board and joist resulting in failure even when the deck boards still have plenty of life left in them.

Make sure the joists are actually treated to UC4 - 'tanalised timber' or other such phrases are all but meaningless.

[C0ffin D0dger]

option click said:

I built something more or less the same size a few years ago, although my middle supports rested directly on an old patio.
Supports look fine - in fact I used fewer and mine hasn't shifted an inch.

I sunk concrete fence posts into the ground and bolted bearers to them - it adds time but it means you don't have any timber in the ground so it should all last longer.

Edited by option click on Friday 31st August 16:15

Edited by option click on Friday 31st August 16:16

That looks really good, nice work there.

[C0ffin D0dger]

Thanks all for the tips etc.

I'm now having second thoughts about it all and thinking of putting in a patio instead

Obviously this would come with the compromise of having to step down onto it from the doors.

The cost is scaring me a bit at the moment. The other issue is that the UPVC Bi-Folds we have aren't the greatest and keep dropping. I can see a point in time when I get completely fed up with them and have them ripped out for aluminium ones instead. Problem is this would be extremely difficult if I've built a deck up to them without pulling up large sections of it up. Obvious solution is to replace the doors first but then we'd have no money for the landscaping and the wife wants it doing sooner rather than later.

[Camoradi]

your frame design looks about right. I used galvanised supports for the legs. (I added further supports in the centre not shown here) The 6 x 2 "supports" left were just temporary to hold it level



When it was all finished, we sold up and moved....