Raised floor off concrete, is DPM or Vapour Barrier req?

[stormfusion]

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• stormfusion
• 12 Jun 2013
• 1

Hi,

I have raised my floor by approx. 22mm using battens off concrete, the battens have approx. 400mm gap between them which is filled by 20mm of celotex insulation, on top of this I plan on using 18mm Chipboard, directly attached to battens.

My house is approx. 20-25yrs old.

My question is, would I require a DPM or Vapour Barrier and if so would I insert this at position 1 i.e. below the celotex or position 2 above the celotex and battens?

Or, am I correct in thinking that there should already be a DPM somewhere in the concrete at position 3 and that therefore the foil front and back celotex would be sufficient?

Thank you.

 

[dann09]

1. why did you raise the floor?

2. were, or are, any signs of damp present?

3. Depending on your BCO, but, typically in my area, raised wood floors off ground floor concrete are required:
to be a min. of 90mm to 150mm off the concrete
have a DPM laid on the concrete
and thro ventilation.

4. have you thought thro the knock-on consequences of a raised floor for door thresholds, and cabinets etc?

 

[stormfusion]

Hi,

1 and 4. The floor was raised to create sectioned living spaces if you like, there are no doors leading onto the first raised area (the lounge) off the lounge is an archway which leads to the dining room, so in terms of doors etc these are not effected, as for furniture we like to keep it very minimal anyway.

2. I did not notice any damp, having said that would not be 100% sure what I would be looking for!. The original flooring directly onto the concrete was some sort of mat with black back, and about 3mm of soft material and then laminate flooring laid on top.

 

[dann09]

Hi,
sorry, i jumped to the conclusion that you were referring to a kitchen floor.

A platform such as you describe, with the conditions of a mature slab and no moisture, then go ahead with your proposal, but lay a vapor barrier below the battens.

 

[stormfusion]

Hi,

Thanx again, just 2 quick more questions, would there not be a DPM inbedded in the concrete somewhere anyway?

Would the FOIL back and front of the Celotex not be sufficient to reduce moisture passing eitherway for 90% of the area?

 

[dann09]

Yes, esp. if the house is post 1970, say. Some houses before that date had membranes, but that's a reasonable cut-off date.

You can, typically, notice the upstand edge of the DPM behind skirting.

Any moisture in the slab, or coming thro the slab will decay the battens and find its way thro any chinks, excepting a membrane, nothing is 100% - but, as above, dont sweat it, give it a go.