Wooden floor on Foundation - Ground level?

[Job]

Hello,

 

trying to figure out a possible wooden floor on foundation construction. Given limitations on allowed building height, I'm trying to win as much vertical space as possible.

One thing that could help in this is lowering the ground floor as much as possible, and I have come up with the following draft, further detailing may be necessary, dimensions can change...

 

My main concern are moist issues, arising from wooden beam floor starting at about ground level...  

Any opinions on this approach are greatly appreciated! 

 

 

 

 

[Hobbiniho]

normally the floor joists would extend all the way out and the wooden "kit" wall would sit on top of the timber joists, what you have drawn has a massive cold bridge and is overly complicated, is it possible to lower the outside ground level to well below the joist level to maintain the DPC.

[ProDave]

This looks like a candidate to ditch the wooden floor and make an insulated concrete floor instead.

[Job]

2 hours ago, Hobbiniho said:

normally the floor joists would extend all the way out and the wooden "kit" wall would sit on top of the timber joists, what you have drawn has a massive cold bridge and is overly complicated, is it possible to lower the outside ground level to well below the joist level to maintain the DPC.

 

What you mean is something like this? What should be a minimum distance between the underside of the joists and the ground soil?

 

[TonyT]

150mm

[Russell griffiths]

I think this all needs a rethink, if you are restricted on height you need a concrete slab type foundation to get it low. 

[Mr Punter]

Once you start to sink the ground floor you almost need to treat it like a basement for waterproofing purposes.

 

Can you sink the surrounding ground?

[fiaraziqbal]

1 hour ago, Russell griffiths said:

I think this all needs a rethink, if you are restricted on height you need a concrete slab type foundation to get it low. 

I have gone down this route and forgone the timber base for exactly those reasons.

[Bitpipe]

You've drawn something similar to our GF detail but it is over a basement.

 

We have a timber soleplate on top of the basement wall, the pozi joists hang off that (the top chord is longer than the bottom) and the deck goes on top. TF walls build off the deck. DPM and airtightness lap under the soleplate 

 

To exterior we have paving that comes level with front door and rear slider but the rest sits away from the wall by 100mm with a 100mm deep french drain. Paving slopes away from house and in the areas where paving is close to exits, DPM is lapped up so no water can get to the wooden elements. Also have lead flashing under the doors.

 

Not had any issues in 5 years even when the rain has been hammering against the door.

[markocosic]

Sounds like a candidate for a solid ground floor to me.

 

 

If going timber floor though...sit the walls on the footings; run the airtightness layer down the wall, then hang the joists off the wall or sit them on the footings? This is less of a cold bridge than running your joists through the wall. Ditto at first floor level with ledgers; flipping your airtightness layer over the top of the header plate (on the ground floor) and under the sole plate (on the first floor) to keep it contiguous. The platform framing approach (with joists sat on top of footings and wall sat on top of joists) was used before the days of structural screws / joist hangars / airtightness etc.

 

 

 

http://blog.lamidesign.com/p/swedish-platform-framing-info.html