Ventilating Suspended Wooden Floor

[Alex H]

I intend to create a suspended wooden floor in the corner of our barn that will become a lounge area.

I know that I should ventilate the void under the floor, to prevent all sorts of nasty rot problems.

In a regular brick skin building this is done with vents through the brick.

However, I only have one outside wall in this room (semi-detached barn onto another house, and 2 internal walls) and its 60cm of stone.

Any idea how this can be done? [8-)]

[mint]

TP, as far as I know and I have seen this done in various situations, this is what you do and I am happy to hear other people's suggestions.

You lay a heavy duty waterproof membrane on the floor.  Then you lay soft wood battens on top of strips of a substance like conveyor belt material (I believe there is a proprietary make called Visquene).  Then you use whatever wood floorboards you have chosen.  For the very poshest looking floors, you have tongued and grooved boards which are secret nailed.

The space under the floorboards created by laying the battens on first allows ventilation. 

So that the floorboards do not buckle up at a later date, you do NOT fix the battens in anyway.  Leave a small space at the edges before you put on the skirting boards.

If you do it right, you will have a perfectly sprung wooden floor that would be the object of envy and admiration of friends and foes alike.

Good Luck! 

[BIG MAC]

You say in a corner of the barn? therefore you will have a change in level between the suspended floor and the remaining?

Dependent upon available space // water table etc. there are a number of options available.

I note suspended floor rather than floating floor so imagine you intend to use joists and there is a significant sub floor solum / void?

Ideally you want to establish 'Cross ventilation' this way differing air pressures at the vents will introduce currents of air in the sub floor (That's if you must have a sub floor - I wouldn't neccessarily)

If the void is less than useable you may be better to fill it with well compacted hard core to a level that would permit blinding with sand putting in a 1200 guage poly membrane (Visqueen or similar) then an RC concrete slab/ rigid insulation battens then floating flooring.

If you are creating a mezzanine or platform (Works for suspended floor goes without saying) then you will have the opportiunity to access two or three sides dependent upon configuration and be able to duct to the outside using simple flat duct inserted at the periphery and take up to the eaves / loft to discharge to atmoshere , the ducts would need to be boxed in but would provide an area for dropping services mounting sockets etc.Really depends on the look you are going for. If fully dry lined then the ducts just run behind the MF framing.

There's any number of ways of doing this so I have gone for the two I consider easiest and hope that these helped.

Cheers

 

[mint]

Ah, sorry Mac & TP.  I jumped to the finished floor as it was a subject I'd discussed over dinner only a couple of nights ago.

Good sound advice from Mac, that's for sure.

[Alex H]

Ok - thanks for the replies - here is a picture which may clarify what I'm trying to do

The thick wall is the wall to the outside. Green lines indicate grey water / soil pipe to the fosse. Orange line is proposed route of soil pipe from 1st floor

What I was proposing was to suspend the floor on brick / blocks piers (giving free flow over all the floor) with the joists running from top of the picture to bottom (hence floorboards run along the room rather than across)

If I do this can I ventilate at the barn end, (RHS) rather than go through 60cm of stone? Do the vents have to go into the 'real outside' ?

Mac I see what you are saying with the flat duct, but is my idea feasible? (it would be rather simpler!)

There is would be very little void under the floor, but the pipes currently stop me making it level with the rest of the house.

[BIG MAC]

Sweet no problems I was simply expanding upon your theme!

TP I can't see images at the mo (Works firewall) but will take a look over the hols and see if the images inspire me, if that's ok?

Cheers,

[BIG MAC]

Dependent upon levels I would say this is a candidate for the hardcore treatment. Just ensure that the hardcore stays about 100mm from the pipes and that you use self compacting material (ie, pea shingle) around the pipes. You would have to cast pads and fasten wall plates etc using your original proposal so this is easier. Dont worry about pipe access as if the worst came to the worst you would simply acces via the chamber and either resin line or pipe burst a new MDPE liner in. This will allow an insulated floor and no void to worry about and floor boards could be diagonal if you wanted!

[Alex H]

[quote user="BIG MAC"]Dependent upon levels I would say this is a candidate for the hardcore treatment. [/quote]

Is the hardcore always required and what purpose does it serve? I say this because I had to use an SDS drill / chisel to dig the trenches for the sink & shower drains [:)], the ground is that hard.

[BIG MAC]

6 million dollar question that one! it depends upon what you are faced with  ie. bedrock not a lot of point I grant you!

Hardcore provides a resilient and level  formation from which to cast a slab and is imminently cheaper than the alternatives whicgh are self compacting material or concrete. You may elect to use a self compacting material such as 50mm sieve river washed stone which would work well in this scenario. If you are concerned about the crown level of your waste pipe then you could always shutter the pipe and cast either side, your insulation and battens which will still pass over the pipe chase but the slab would no longer be a monolith and may present some differential movement dependent upon the formation beneath it. Your floor in all scenarios will have the look of a finished timber floor  but wont be as draughty as a ventilated sub floor and will be insulated as well, you will be able to turn your DPM (Damp proof membrane up at the sides leaving an excess sufficient to allow for insulation flooring and skirtings (If walls permit) which once fastened you can trim off the excess, decorate and mastic the top. It's the easiest and cheapest way.

Hope this helps

[Alex H]

Thanks for that - it's been a great help. I'll let you know the result if I ever get round to finishing it!

[BIG MAC]

No Problem, Have a great Christmas ( I dare say a large part of it may be spent plotting France 2010 by the sounds of it!)