is a damp proof membrane required on top of bison beams?

[downinalbion]

A friend of mine is having a house built for him at the moment.The ground floor has bison beams.Under this floor is a 3 foot void and a concrete oversite.
The bison beams were laid on a DPC.On top of the bison beams there is 100 mm of kingspan then underfloor heating and then a concrete screed.
I didn't say anything to my friend at the time as i'm not entirely sure,but i thought it was normal procedure to cover the floor with visqueen before the insulation went down.
I know in theory the DPC under the beams should form a barrier from moisture,but this can easily get damaged when placing the very heavy beams on it.
Do people think this lack of membrane is an issue?

 

[freddiemercurystwin]

Not for a suspended floor, the void beneath should be ventilated and hence dry unless the ground beneath the floor has been dug out to a level below the surrounding existing ground level and the void is not to be drained. As you say there should be a dpc in any walls supporting the beams anyway, besides there's just as much chance of a dpm under a slab getting damaged during construction as a dpc in a wall.

Read it all in black and white here:
http://www.planningportal.gov.uk/Pp...portal.gov.uk/uploads/br/BR_PDFs_ADC_2004.pdf
page 27

 

[mater]

there should be one there to stop moisture, it can go under the insulation or on top of it

 

[downinalbion]

thanks for replys people. p27 states that a ventilated void underneath is adequate,so on this basis it should be fine.
There is a DPC under the beams,but still feel this is more vulnerable than a membrane and foot traffic, to puncturing from the rough underside of the beams,especially when they are nudged to get them into the correct position.
If it was my house i would opt for belt and braces, DPC and membrane,but it isn't,so ill keep stum on this one.Dont want to cause any trouble.

 

[downinalbion]

there should be one there to stop moisture, it can go under the insulation or on top of it

do you mean moisture from the air?

 

[freddiemercurystwin]

If it was my house i would opt for belt and braces, DPC and membrane,but it isn't,so ill keep stum on this one.Dont want to cause any trouble.

Thats fine but in reality thousands of houses are constructed every year like this with only a dpc on the sleeper or perimeter walls without incurring any problems later. There's a time and a place for belt and braces, this is not really one of them though.

 

[downinalbion]

If it was my house i would opt for belt and braces, DPC and membrane,but it isn't,so ill keep stum on this one.Dont want to cause any trouble.

Thats fine but in reality thousands of houses are constructed every year like this with only a dpc on the sleeper or perimeter walls without incurring any problems later. There's a time and a place for belt and braces, this is not really one of them though.

This is very reassuring,and as i said i just wasn't sure.The last thing i wanted was for there to be problems in the future and to have not mentioned anything to my friend during construction.
Thankfully it sounds like i have nothing to worry about... phew