floorboards - ventilation gap around edge of floor

Postby benny » Tue May 29, 2007 9:59 pm

I have laid floor boards in a room but I am now worried that there should be a gap between floor boards and the walls around all four walls of the room for the air to flow through. I have left 2-3mm and you can slide a saw down the gap between the wall and the floorboards, will this be enough for the air to flow through? two of the walls are dry lined with batterns and polysteyrene, the batterens only touch the walls where the hammer fixings go through wooden blocks so there is a 5-15mm gap between the solid wall and timber wall frame, the air can flow freely from the roof behind this dryling. I am very nervus that if the 2-3mm gap around the floor isnt enough the air circulating from the loft and behind the drylined wall is going to sweat and give my floor boards dry rot, am I being stupid? or should there be more of a gap? can the boards expand getting rid of the gap all together?
Any thoughts on this welcome thanks
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Postby thedoctor » Fri Jun 01, 2007 10:18 am

Absolutely no need to have any gap whatsoever Benny, in fact most people spend their lives trying to fill up the gaps. Each room should be ventilated in itself. You dont say what room it is. The wall ventilation is an entirely different propsition to the floor and any air rising from the floor up the wall will be warm anyway so it will not give the ventilation properties you require., It might be easier to explain exactly what you are trying to achive with ventilation and then maybe we vcan help more. A stud wall built afgainst a brick wall should either have a vapour barrier and a full 50mm of free flowing ventilation from top to bottom or be solidly insulated using something like thermal board. Its not possible to direct warm air, through floorboards up into stud wall cavities. Recycling warm air will lead to problems.
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Postby benny » Mon Jun 04, 2007 12:41 pm

Thanks for the reply. The room is an upstairs bedroom, is the air under the floor warm then? does there need to be ventilation behind the drylinning on a wall so the insulation doesn't sweat? I thought the air needed to flow from the loft behind the dryling and through the floor is that wrong? I just didnt want heat or moisture in uncirculated air behind the drylinning incase of dry rot problems.
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