Steel or PT sub-frame for elevated deck?

MayoForSam

I'm building an elevated deck at first-floor level of a holiday home. I was originally going to build a pressure treated (PT) timber sub-frame using 9x2's for the outer frame and 6x2 joints on 16" centres (deck size is 2.4m x 4.8m). The deck itself will be made using composite boards and I was also going to support the deck with 4 galvanized hollow steel columns (100 x 100) on concrete footings with the near side attached to the wall of the house.

However my missus has got it into her head that a steel sub-frame would be better and last longer. However, this would be a lot more expensive, probably heavier and more difficult to install (e.g. attaching the decking boards to the steel joists). I can build the PT timber frame myself, put some DPC over the joists for waterproofing and the frame should be well ventilated and dry out quickly, it should easily last 10-15 years.

Can anyone recommend the best way to go - steel frame or PT timber?

Calahonda52

what's the wall thickness of the box?
I would be looking at 6 " box?
what X bracing have you in mind for the outer pair of uprights?
what's the plan for the balcony?
to eliminate twisting, warping what about accoya, dearer than rough but easy/lovely to work with
http://www.abbeywoods.ie/accoya/

listermint

Personally I wouldn't build a deck in this country where the supporting beams are timber and exposed to the elements especially at first floor level. No from me. The climate will eat it alive.

Having lived in apartments where the timber balconies were giving way everywhere it's just not a long term approach.

I'd spend the money and do it right..your Flooring can be Composite for the look and longevity

MayoForSam

4 steel column box supports will be 100 x 100 x 6 box section, 2.5 metres high, bolted to the rim joist at the top and to the bottom concrete pad using a base flange plate. Not decided on the balustrade yet maybe hardwood posts and metal railings or else glass panels/stainless steel posts and top rail.

The PT wooden sub-frame would not be directly exposed to the elements as the composite deck would cover it on top and it would also have a fascia also made out of the same material. I've seen lots of all-wooden decks in the US and Canada that are a lot bigger and open to exposure.

listermint

MayoForSam wrote: »

4 steel column box supports will be 100 x 100 x 6 box section, 2.5 metres high, bolted to the rim joist at the top and to the bottom concrete pad using a base flange plate. Not decided on the balustrade yet maybe hardwood posts and metal railings or else glass panels/stainless steel posts and top rail.

The PT wooden sub-frame would not be directly exposed to the elements as the composite deck would cover it on top and it would also have a fascia also made out of the same material. I've seen lots of all-wooden decks in the US and Canada that are a lot bigger and open to exposure.

Don't make the mistake of us and Canada comparison to our climate. It's vaaaaastly different. Our humidity levels are pretty out there hot or cold this is what ruins timber.

chooseusername

At first floor level might it need planning?
it would in UK anyway as far as I know.

MayoForSam

chooseusername wrote: »

At first floor level might it need planning?
it would in UK anyway as far as I know.

I got planning permission a month ago.

GreeBo

Is 10-15 years all you want to get out of it?
For that level of effort I'd never want to look at it again...