Polythene or Builders Paper between Insulation and UFH pipes?

A

apple1

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Folks,

Almost in a position to lay UFH piping (when I get two consecutive dry days!). Would appreciate any opinions on whether I should fit polythene or builders papers between the insulation & UFH pipes? Is there any possibility that the polythene would sweat if I fit it? If there is no difference, what guage of polythene should I use? Thanks in advance, apple1
 
I wouldn't bother with either if insulation is tightly butted together there will be no problem with concrete seeping into gaps. you could also just tape all the insulation joints as a cheaper option. Weather looks good from Friday onwards so you might get the pour done then.
 
Thanks rahman. I did read somewhere that a layer of something should be fitted between the two so as to allow the screed settle independently of the insulation below? Doubt if I'll get the pour done at the weekend. If its (the weather) good though, I may just get the UFH pipes laid and then be ready for our the next time we're blessed with a dry stretch.
 
I would prefer to see a vapour barrier of some kind go over the insulation before screeding, this prevents moisture take up by the insulation and will prevent the screed drying out too quickly. I would imagine that 1000 gauge DPM would be more than adequate for this purpose.
 
This breather paper method is the norm in Britain. im not entirely sure of its purpose though.
 
Yes breather paper is the norm in Germany as well. The idea being just to stop the insulation swimming if any grout gets in behind. The joints should overlap by 100mm and the paper should go up the wall about 150mm. A ribbon of corrugated paper or foam would skirt the bottom of the wall by 100mm ....... expansion I would imagine. Any pipes coming through the floor should be lagged and the joinings made waterproof with masking tape. You don't want to have major stalactytes and stalactmites in the room underneath.
 
Syd/Carpenter,

Given my other post that you contributed to earlier regarding the existing dpm being punctured, I presume that you both would recommend using 1200 guage polythene between the insulation & screed. Just thinking out loud here, won't this, i.e. the secondary screed be punctured also when securing the UFH pipes to it? I know the holes are pretty small, but it'll be punctured nonetheless???? Am I too concerned about having it perfectly sealed??
Thanks, apple1
 
apple, as far as laying a breather paper membrane between the UFH and insulation, i would say it doesnt matter. I wouldnt lay a DPM here, because the insulation may get compromised by rising moisture due to your punctured first DPM. You UFH manufacturer should recommend the construction, but this is the way i would go.

Floor Finish
Screed (easy screed if possible... the thinner the better for UFH)
UFH system
Insulation
DPM
Concrete Slab
punctured DPM (probably useless at this stage)
compacted hardcore
 
Syd...thanks once again for the advice. Major pain in the you know whats to have to lift insulation and fit a 2nd dpm, but better to address the issue now I guess. Just out of curiousity, what would have been the implications for my build had I not became aware of the puncture holes in the original dpm?
 
If the insulation becomes wet it may be compromised. It definitely would result in a reduction in its thermal performance.... It is expected that the gas in the PU boards exhaust over time, and if the insulation becomes wet then water and not air will take the place of the gas. Depending on the extent of compromising, it may even disintegrate, which could cause the floor to sink... bad news all round.
 
Thanks Syd. Its just dawned on me that the services are in place at this stage (i.e. above subfloor level). I'd appreciate any suggestions as to how I'd go about fitting the 2nd dpm
given that these pipes (primarily waste) are now all in situ? Do I just lay the 2nd DPM down over them & then cut & seal around the stacks? What a mess!!!
 
so all the sink waste pipes, SVPs etc are in place already???? damn.....
If its just SVP upstands then thats all right.....itsnot a big job to cut around and seal these... but if sink waste pipes are there already it is a messy job, especially if the waste pipes are not at external walls.

The whole idea of the second DPM is to protect the insulation.... the plumber caused this mess so he should not give you any stick if you ask him to uproot any awkward plumbing. The insulation HAS to come up.
 
Yep Syd...all wastes, sink & SVP's are in situ. Ducting for vacuum system also! All the sink & shower wastes are running into 4" soil pipes that are cut flush with the subfloor & fitted with rubber caps that the sink wastes sit into. Fitting over the SVP sounds relatively simple (just get a good seal) but what about the sink wastes? Any ideas - I could use some
 
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