Now there is a lot of confusion over where you can use a DPM what are the companies saying..... If they are saying a new sub floor is needed, what is best way to have it done? If you tell customer that an they won't have it done what can we do then? I have done f.ball an laybond systems an not had a problem but that's not to say in 5 Years LVT's might gap or lift. What about jumpax system for LVT's?
Ive used jumpax with membrane sheet underneath a few times and that saved alot of prep work to a damp floor with a bad existing screed
Was on the phone with F.Ball and laybond today F.ball said its ok the system with F75 as long as old ata adhesive was removed Laybond said the same, remove old adhesive, black magic , 2 coats of 1 coat membrane. Can someone find out about uzin and mapei?
When I say damp I dont mean soaking wet but for instance the last one I did the subfloor was reading 78% so I thought rather than have to rip up the whole screed as there was a builders latex already existing I would use Jumpax with a vapour barrier.
Have you told them you want to use the surface DPM on a wet/damp floor that DOES NOT have a DPM to start with. Or have you asked them can you install Surface DPM on a Wet subfloor that does still have a DPM under it? Don't confuse the TWO. O and the Answer to Mapei and Uzin is no. I was with Mapei last week inspecting a failed DPM that had been laid on a subfloor with no DPM under it. I will post up a pic of the failed LVT in a minute for you!
Spoke to the balls guy at the scottish floor show last week bout this He said pre '65 houses with no dpm should be 2 coats 75, and post '65 with hi readings should be 2 coats 75 So only way not to have 2 coats 75 is to have normal readings, otherwise 2 coats 75! lol
I wish they would make up there mind. Do they have this in writting ? Also what are they saying to use for a prep before the F75 ? Say on quarry tiles or a rough surface screed/concrete floor ? They used to say 131 primer and then 200 acrylic. But these started to fail due to the 131 primer breaking down after a while. Then they brought out DPM prep 900 that was used without primer. This failed also ! So if what they are telling you is true ask them how to prep the subfloor and see what they say.
quote Have you told them you want to use the surface DPM on a wet/damp floor that DOES NOT have a DPM to start with. Or have you asked them can you install Surface DPM on a Wet subfloor that does still have a DPM under it? Don't confuse the TWO. I will post up a pic of the failed LVT in a minute for you![/quote] Yes Matt told them what do you do over a floor with no dpm under it. Same question was to laybond. I have not asked them about a wet subfloor, just on a standard pre 1965 house.
I asked that an answer was green bag but he didn't mention primer and black magic. Bet they wont do it in writing though
Here you go, some pics of the subfloor that i was looking at last week. The subfloor was primed and then a latex smoothing compound used. Next a surface DPM and the the LVT was glued direct to the DPM. All 3 products worked as they should but the pressure of moister underneath built up and actually sheared the very top layer of the quarry tiles and even managed to pull the grout out of between the tiles. What you have to remember with water is it will try and level itself out. If the subfloor in question is below the outside ground then you will have increased water pressure / vapiour trying to push it way up.
Maybe this picture will help. Sorry its not the best! Now water will always find its own level. As i have said before, depending on where the house is built and what sort of moister is in the ground around it etc (water table) All this will make a massive difference to weather teh surface DPM will stay down or not. In a house with a DPM already installed you will have a few inches of concrete to weigh the dpm sheet down. Obviously if its a surface DPM you dont have a few inches of concrete to weigh it down. You have maybe 3mm of smoothing compound hence it can be pushed up and fail. Now if the house is sitting higher than surrounding earth then you will have a a lot less pressure trying to push up. you may have simular Moister readings as your reading how much moister vapiour is escaping through the concrete slab. Your not measuring how much vapiour pressure is there. Think of how a steam engine works and how powerfull water pressure/vapiour can be! In the case above you may not have any issues using a surface DPM over a subfloor with no DPM, simply because you have very little pressure there. :|
nice post matt thanks So your saying if we get high readings in a house thats pre '65 and in a valley, then to promptly run out the door screaming? :lol:
The issue is that you may get low readings, I say low but i still mean above 75%rh. The problem comes with the pressure build up after you install the surface DPM. So yes, run off screaming!
So they adviced you to use green bag? O.k then. Read this, these are Fballs instructions for using Green Bag! When STOPGAP GREEN BAG is used under STOPGAP Waterproof Surface Membranes; absorbent concrete and sand/cement screeds must be primed with STOPGAP P131 diluted 1:7 with water. Non-absorbent surfaces and power floated concrete must be mechanically treated in accordance with the F. Ball Subfloor Preparation Guide. Now did Fball tell you that you have to prime the subfloor? With 131 that you cant use on damp floors ? Ask FBALL about there 131 and if you can use it on damp floors and they will say NO. So how can you lay Green Bag then ? :shock: :idea: :roll: :lol:
Hydrostatic Pressure type it into google and read about it this will help you understand, and nothing holds back hydrostatic pressure.
As alot of the houses in my neck of the woods is pre 1965 I have been using alot of DPMs and never had a fail yet. Not to say I wont but I have laid plenty of floors with no DPM an even in my old house which I screeded with screedmaster 2 and laid van gogh, I rent it out and its still down after 10 years. fair enough it might not be fool proof but what else can you do, apart from taking sub floor up? I cant walk away or would lose alot of work.
