deck extension - bracing?

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New Member
Jul 15, 2009
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Hi all!

your input about my idea will be highly appreciated.
I apologise for the dimensions being in metric system.

the house sits on poles approx 2.5m above ground = 8 ft, with garage under the house. in total there are 9 poles, three each side and three more along the ridge. On one side of the house there is a 1.6m (5 ft) wide deck approx 9m long (30 ft). I want to enlarge one half of this deck, between two poles only. Distance between the poles is 4.3m (14 ft)

It would be so easy with posts at the other end to support the new structure, but for multiple reasons, I would like to avoid that.

You can check the following photos to see what I want:
- existing cross-section:
- proposed alteration:

Please note the existing deck has the joists on the cantilevered end of the beams supporting the house (2 beams 12x4 on each pole) with a space of around 6 inch between them. I am thinking to slide the new beams into that gap and bolt it toghether, between the the existing beams.

I can also allow for an extra bracing to stiffen against lateral movement if required. I will not build it myself, it has to be designed / sized and approved but I want to have an ideea about how far from a normal design I venture here...

Any feedback will be appreciated.



Jan 9, 2010
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All decks need to be supported by direct bearing. Post under the deck. Any other way requires engineering and that is not a fool proof science or we would't have bridge collapses. Should you build your idea or force it down a contractors throat, under the premise that " they won't get the job it they don't build it the way i want", Than you should be prepared to pay for the medical expenses when and if it fails. You can see some of the results of great deck engineering by visiting the site
steve scholl

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