Inside of DPM Soaking Wet (Condensation Problem? Fix Needed)

daveJL

daveJL

New Member
Hi all,

We are currently renovating a downstairs 1920 (ish) flat and have had damp proof membrane fitted by a local company. Plasterboards were then dot and dabbed onto the membrane and plastered.

The inside of the DPM is now soaking wet when you put your hand up the cavity between the DPM and plasterboard. Wet patches are present on the floor around the edges of the affected areas where moisture is running down the DPM.

We've also got some mould growing around the unplastered bottom edges of the plasterboards and some small spots up the walls as well. DPM is full height in the kitchen (I thought this was overkill but its the damp companies guarantee and that's what they said to do so we rolled with it) and half height in other spots.

Video I took of the problem today:

The property is of brick construction, two layers thick with no cavity between them. The DPM has been drilled into the internal brick.

My theory is that the DPM is cold as there's no insulation in the walls therefore condensation from water vapour inside the property is forming on the DPM as it can't move through the wall and get out. The DPM is effectively keeping moisture in as well as keeping it out.

Just to be clear the construction is as follows:

External Brick
Internal Brick
DPM
Platerboard (dot dabbed so a cavity is formed)
Plaster

Has anyone encountered this problem before? Can anyone suggest a fix?

FWIW we have retro-fitted trickle vents and added pacifier vents but the problem remains (although condensation from windows has ceased and relative humidity is at a normal level (35-50%).

I'm feeling like we need to add some kind of insulation. Which means all the boards will have to come off and maybe even the DPM?

Not sure where to go on this one so any help much appreciated.

Cheers

Dave
 
AHH bit far away..

Looks like plastic membrane laps onto floor in video

If you just have a rising damp (above ground damp) situation then I would leave a little gap to allow air flow
Insulated plasterboard may also help in your situation

Can you get the company back to have. A look .?
 
daveJL said:
Hi all,

We are currently renovating a downstairs 1920 (ish) flat and have had damp proof membrane fitted by a local company. Plasterboards were then dot and dabbed onto the membrane and plastered.

The inside of the DPM is now soaking wet when you put your hand up the cavity between the DPM and plasterboard. Wet patches are present on the floor around the edges of the affected areas where moisture is running down the DPM.

We've also got some mould growing around the unplastered bottom edges of the plasterboards and some small spots up the walls as well. DPM is full height in the kitchen (I thought this was overkill but its the damp companies guarantee and that's what they said to do so we rolled with it) and half height in other spots.

Video I took of the problem today:

The property is of brick construction, two layers thick with no cavity between them. The DPM has been drilled into the internal brick.

My theory is that the DPM is cold as there's no insulation in the walls therefore condensation from water vapour inside the property is forming on the DPM as it can't move through the wall and get out. The DPM is effectively keeping moisture in as well as keeping it out.

Just to be clear the construction is as follows:

External Brick
Internal Brick
DPM
Platerboard (dot dabbed so a cavity is formed)
Plaster

Has anyone encountered this problem before? Can anyone suggest a fix?

FWIW we have retro-fitted trickle vents and added pacifier vents but the problem remains (although condensation from windows has ceased and relative humidity is at a normal level (35-50%).

I'm feeling like we need to add some kind of insulation. Which means all the boards will have to come off and maybe even the DPM?

Not sure where to go on this one so any help much appreciated.

Cheers

Dave
Click to expand...

What was the purpose of the DPM? Existing damp problems?
Seems like a bad idea to put a plastic bag around a room which of course will trap moisture. Do you have ventilation that room?
 
martinemj said:
AHH bit far away..

Looks like plastic membrane laps onto floor in video

If you just have a rising damp (above ground damp) situation then I would leave a little gap to allow air flow
Insulated plasterboard may also help in your situation

Can you get the company back to have. A look .?
Click to expand...

Hi Martin,

The company who did the work can be called back but my confidence in them is very low as everyone who worked on the job were subbies and in a rush.

We had some damp issues in the walls and damp meter readings were poor in a lot of areas which is why it’s full height.

The issue is the video is occurring even where the half height membrane has been applied to external walls.

I’m at a bit of a loss about what to do with it.

Taking it off and putting insulated boards on is an option but we don’t have the funds to rip out, fix up and have the same issue again.

The membrane isn’t tucked into the flooring even though it’s cut very close to it.

I’m guessing it’s never going to dry out in its current state?
 
worthwords said:
What was the purpose of the DPM? Existing damp problems?
Seems like a bad idea to put a plastic bag around a room which of course will trap moisture. Do you have ventilation that room?
Click to expand...

Yes existing damp problems is why we have the DPM.

The room has trickle vents in a single widow and a pacifier vent. Doesn’t seem to be helping though.
 
A lot of damp company's use the newton membrane as its a diy job.... Dont need to be a trade to install it........ They tell customers damp cant come through it and you can decorate it in just a week..... Whilst those point's are true its not a good practice......i often comment on Facebook adverts of damp company's asking why they tank every job..... And its the same response about the speed of the job.......... I prefer a good job ,not a quick job....
 
daveJL said:
Hi all,

We are currently renovating a downstairs 1920 (ish) flat and have had damp proof membrane fitted by a local company. Plasterboards were then dot and dabbed onto the membrane and plastered.

The inside of the DPM is now soaking wet when you put your hand up the cavity between the DPM and plasterboard. Wet patches are present on the floor around the edges of the affected areas where moisture is running down the DPM.

We've also got some mould growing around the unplastered bottom edges of the plasterboards and some small spots up the walls as well. DPM is full height in the kitchen (I thought this was overkill but its the damp companies guarantee and that's what they said to do so we rolled with it) and half height in other spots.

Video I took of the problem today:

The property is of brick construction, two layers thick with no cavity between them. The DPM has been drilled into the internal brick.

My theory is that the DPM is cold as there's no insulation in the walls therefore condensation from water vapour inside the property is forming on the DPM as it can't move through the wall and get out. The DPM is effectively keeping moisture in as well as keeping it out.

Just to be clear the construction is as follows:

External Brick
Internal Brick
DPM
Platerboard (dot dabbed so a cavity is formed)
Plaster

Has anyone encountered this problem before? Can anyone suggest a fix?

FWIW we have retro-fitted trickle vents and added pacifier vents but the problem remains (although condensation from windows has ceased and relative humidity is at a normal level (35-50%).

I'm feeling like we need to add some kind of insulation. Which means all the boards will have to come off and maybe even the DPM?

Not sure where to go on this one so any help much appreciated.

Cheers

Dave
Click to expand...

How long has the plaster been dry? The air will be a lot more humid while until it’s all dry.
Next thing is there anyway there could be a leak from the flat above? It’s quite a lot of water for condensation considering you’ve trickle vents
 
I use this material myself a few times a year..
there are a few ways to use it and I have a preferred method I use.


So I guess you have...

Room is above ground and just some rising damp
Solid walls with no cavity

Once fixed the damp/water should be contained on the masonry side of the membrane

In a cellar type situation you would drain to a sump
In a rising damp situation (no running water on membrane)you are venting at ground (just cut it short of ground by 10mm)

You do need some air flow as this will stop condensation forming
Ideal to insulate too between membrane and plasterboard if you can

We only use this product where the wall is below ground
On above ground we would go the lime route and hack off back to masonry and start from there


From your clip I looks like it's wet behind plasterboard which is a worry ..wrong side of membrane

Either leak from the water pipe(looks new )

Are there any pipes behind plasterboard we can't see

Is there heating in the room at all.......


Martin
 
Hi Martin,

Thanks for the reply. There's no pipe work behind those boards and there’s no leak either. It was just brick before the DPM and membrane went on.

The DPM has been fitted in three rooms and is wet behind the plasterboard in all areas where fitting has been done on external walls.

There is no radiator in the room in the video but the boiler is in that room. Other rooms have radiators but the same problem still remains.

Thanks

Dave
 
Tinytom said:
How long has the plaster been dry? The air will be a lot more humid while until it’s all dry.
Next thing is there anyway there could be a leak from the flat above? It’s quite a lot of water for condensation considering you’ve trickle vents
Click to expand...

Im pretty sure it’s not a leak as the same problem is present throughout the property.

Plaster has been dry over a week and moisture on DPM shows no signsof drying up.
 
daveJL said:
Yes existing damp problems is why we have the DPM.

The room has trickle vents in a single widow and a pacifier vent. Doesn’t seem to be helping though.
Click to expand...
You need to address the damp problems before sealing it up. Inner cavity wall should be dry so either penetrating or humidity but also early cavity walls had nasty things like rat trap bonds instead of wall ties and so need to treat them more like a solid wall.
 
As discussed in the other recent tanking topic - it sounds/looks like a condensation issue, commonly associated with tanking membranes.
Water vapour generated (inc wet trades/plastering water) will condense on a cooler surface (when below dew point), and unless you create an airtight wall, vapour can ready pass and cause sub-surface condensation (interstitial condensation).

I’ve seen it often, usually not an appropriate specification for traditionally constructed properties.
 
earthy said:
As discussed in the other recent tanking topic - it sounds/looks like a condensation issue, commonly associated with tanking membranes.
Water vapour generated (inc wet trades/plastering water) will condense on a cooler surface (when below dew point), and unless you create an airtight wall, vapour can ready pass and cause sub-surface condensation (interstitial condensation).

I’ve seen it often, usually not an appropriate specification for traditionally constructed properties.
Click to expand...

Thanks for the reply. Appreciate all the help that’s coming in this thread so far.

What, if anything, can be done to fix the issue?
 
Reminds me I recently bought a humidity and temperature monitor off Amazon. 12.99

You can work out the dew point once you know the humidity and temp

Got some rooms which are way above on humidity (up to 85%). Should be 60 max
 

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Good Idea Martin,
But, you’ve of course got to know the surface temp also so you’d need at least a digital thermometer for any of that data from your hygrometer (temp and humidity device) to be relevant.
 
Yea this measures room temp

Got a bedroom which I really bad so going to use a 80mm fibre board (breathable) and lime plaster it......
 
Morning Dave,
Fundamentally it’s the wrong specification for your property and therefore should never have been applied. Although these ‘air-gap’ tanking systems can appear to work in theory (work meaning - your decorative finish is no longer spoiled by dampness), in practice, they often exacerbate the problem, moving the dew point and therefore condensation to another point within the makeup of the wall.

Without ripping to stuff out, without being alarmist, the best you can hope for is that condensation you are seeing is largely down to the excess water in the air from the plaster and the problem isn’t has bad once that’s evaporated (how long ago wasn’t it plastered?) or than you control humidity within the room with either passive/natural or mechanical ventilation or dehumidification.

Is it just one room or the whole ground floor?
 
Some good ideas earthy

I would run a dehumidifier for few days and see if it helps or cures problem

I big industrial one......
not a shitty home bargains special
 
earthy said:
Morning Dave,
Fundamentally it’s the wrong specification for your property and therefore should never have been applied. Although these ‘air-gap’ tanking systems can appear to work in theory (work meaning - your decorative finish is no longer spoiled by dampness), in practice, they often exacerbate the problem, moving the dew point and therefore condensation to another point within the makeup of the wall.

Without ripping to stuff out, without being alarmist, the best you can hope for is that condensation you are seeing is largely down to the excess water in the air from the plaster and the problem isn’t has bad once that’s evaporated (how long ago wasn’t it plastered?) or than you control humidity within the room with either passive/natural or mechanical ventilation or dehumidification.

Is it just one room or the whole ground floor?
Click to expand...

Hi Earthy,

Thanks for the reply. The plaster has been dried maybe a week. We've got a relative humidity reading of 60% in the room at the moment but the floor has more drying out to do so I'm hoping this will drop over the next week or so.

I spoke to the contractor who did the damp work this morning and he said this is not an uncommon occurrence and it can take up to four weeks to fully dry out. He said that because the plasterboard is dot and dabbed onto the wall moisture which would usually get sucked into the brick has nowhere to go and condensates on the membrane. It then runs down the membrane until it dries out.

I have put a dehumidifier in the room and plan to leave it for a few days to see if it has any impact. You're right though... at this point I'm just hoping it'll dry out.

What would you say the correct way to do this job would have been?

One big issue with not using the membrane was we had two walls with damp which back onto property / yards we don't own.

Cheers

Dave
 
martinemj said:
Some good ideas earthy

I would run a dehumidifier for few days and see if it helps or cures problem

I big industrial one......
not a shitty home bargains special
Click to expand...

FWIW the only dehumidifer I could get my hands on at short notice was the Xpelair 16L from Toolstation. Not exactly industrial.
 
daveJL said:
FWIW the only dehumidifer I could get my hands on at short notice was the Xpelair 16L from Toolstation. Not exactly industrial.
Click to expand...

Evening Dave,
The dehumidifier should be ok for one room:will help anyway.

The system is wrong for your property - if I’m right in thinking that you where trying to control dampness from abutting walls in the yard of a neighbouring property (?), it’s tricky.
However, If it is ‘wet’ (is it a boundary walk?) your neighbour may be obliged to do something about it, you could explore if your neighbour may be receptive to isolating the abutting wall, if they are difficult, well that would require professional fees, maybe a party wall solicitor... if the above does not apply, the following would be my next consideration regardless:
You would need to quantify the extent of moisture - is it too wet (and/or salt contaminated) for lime plaster inc breathable paint to manage?
If so, what about apply wainscotting or other lining to the problematic wall?

A problem that your contractor has created is that they’ve moved the dew point from the surface of your old damp wall to the room-side face of their tanking membrane, so if the room is humid, there’s a real possibility that you would start seeing circular damp patches corresponding with the plaster adhesive dabs at time of high humidity.

The 60%rh you quote is air temperature, the critical data here is the surface temp of your wall, too low (the dew point shifts according to temp) and moisture will condense on your membrane, even if the rh doesn’t appear too high.

Tricky.
 
Just thought I'd post a little update here...

I think it's pretty clear that from the advice posted in this thread the work that was carried out certainly wasn't the optimum solution to the problem at hand.

If I was ever to use the membrane again in a similar environment at a minimum I'd want insulated plasterboards with a vapour layer installed as opposed to just regular boards. My general feeling is the damp wasn't that bad... was likely caused mostly by condensation problems and boards could have been fitted with foam direct to the brick work without the membrane. Just a guess.

Regardless we are where we are and pulling it all down isn't really an option. Here's what we've done...

  • In an attempt to help the membrane dry out the plasterboards were cut at the bottom to leave about a 650mm gap to the floor.
  • A dehumidifier has been running for a little over a week now and relative humidity is down significantly from above 60% to 48-52%.
  • An electric heater has been blasting hot air up the back of the boards at all times when someone has been in the property.
  • Moisture can no longer be felt if you stick your hand up the back of the boards - if it's happening further up the wall or not is another matter and unconfirmed at the moment. I'm tempted to cut some holes to check but obviously that comes with repair issues.
  • Mould was treated today with a spray and will be repeated in some small spots tomorrow but for the most part has been very effective (planning to use something in my paint to help prevent future problems, suggestions welcome?)

Going forward, given the current Coronavirus situation, work has pretty much stopped on the site so for the next few weeks I'll pop in daily to empty the dehumidifier and just continue to let the flat dry out as much as humanly possible.

My concern is that next winter we could get similar condensation problems on the membrane but I'm hopeful that the majority of the moisture is from the dot and dab and once fully dry we'll be OK. Everything I read says gypsum plaster doesn't allow moisture to move through very well so once the skirting boards are on hopefully moisture won't be able to return to the cavity.
 
daveJL said:
Just thought I'd post a little update here...

I think it's pretty clear that from the advice posted in this thread the work that was carried out certainly wasn't the optimum solution to the problem at hand.

If I was ever to use the membrane again in a similar environment at a minimum I'd want insulated plasterboards with a vapour layer installed as opposed to just regular boards. My general feeling is the damp wasn't that bad... was likely caused mostly by condensation problems and boards could have been fitted with foam direct to the brick work without the membrane. Just a guess.

Regardless we are where we are and pulling it all down isn't really an option. Here's what we've done...

  • In an attempt to help the membrane dry out the plasterboards were cut at the bottom to leave about a 650mm gap to the floor.
  • A dehumidifier has been running for a little over a week now and relative humidity is down significantly from above 60% to 48-52%.
  • An electric heater has been blasting hot air up the back of the boards at all times when someone has been in the property.
  • Moisture can no longer be felt if you stick your hand up the back of the boards - if it's happening further up the wall or not is another matter and unconfirmed at the moment. I'm tempted to cut some holes to check but obviously that comes with repair issues.
  • Mould was treated today with a spray and will be repeated in some small spots tomorrow but for the most part has been very effective (planning to use something in my paint to help prevent future problems, suggestions welcome?)

Going forward, given the current Coronavirus situation, work has pretty much stopped on the site so for the next few weeks I'll pop in daily to empty the dehumidifier and just continue to let the flat dry out as much as humanly possible.

My concern is that next winter we could get similar condensation problems on the membrane but I'm hopeful that the majority of the moisture is from the dot and dab and once fully dry we'll be OK. Everything I read says gypsum plaster doesn't allow moisture to move through very well so once the skirting boards are on hopefully moisture won't be able to return to the cavity.
Click to expand...

Moisture-laden air will pass through unless you can guarantee air tightness, regardless of what materials you use, replacing the skirting will make little difference.

Also we’ve not discussed the dabs that are forming a cold bridge between the wall and the surface of your plasterboard, so next autumn, those dabs are likely to be the coldest part of the wall and are therefore at risk of attracting condensation.

The method is all wrong and not practically salvageable, so the best you can do is try to manage humidity in the room, and obviously, not to repeat the mistake again.

Good luck.
 
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earthy said:
Moisture-laden air will pass through unless you can guarantee air tightness, regardless of what materials you use, replacing the skirting will make little difference.

Also we’ve not discussed the dabs that are forming a cold bridge between the wall and the surface of your plasterboard, so next autumn, those dabs are likely to be the coldest part of the wall and are therefore at risk of attracting condensation.

The method is all wrong and not practically salvageable, so the best you can do is try to manage humidity in the room, and obviously, not to repeat the mistake again.

Good luck.
Click to expand...

We live and learn mate... supposedly brought in the experts to fix this as had little knowledge around the subject when we first started but looks like I got some very questionable advice.
 
daveJL said:
We live and learn mate... supposedly brought in the experts to fix this as had little knowledge around the subject when we first started but looks like I got some very questionable advice.
Click to expand...

We do indeed. Even when these systems appear to be working (defined as ‘decoration is not spoiled’), moisture is accumulating and it’s got to go somewhere, so if you’re unlucky...
Anyway, good luck.
 
brimplas1 said:
A lot of damp company's use the newton membrane as its a diy job.... Dont need to be a trade to install it........ They tell customers damp cant come through it and you can decorate it in just a week..... Whilst those point's are true its not a good practice......i often comment on Facebook adverts of damp company's asking why they tank every job..... And its the same response about the speed of the job.......... I prefer a good job ,not a quick job....
Click to expand...
I have my own damp company and almost every I go to that has failed is a membrane system that hasn’t been installed correctly. The water vapour it creates causes more problems than the damp they tried to fix
 
Hi pal, we had this problem a few months back. Basically we did a job using this type of membrane. We actually used thermal backed boards so the problem will still persist even if you fit them. Basically this is just condensation from the room being too cold. it was solved when we introduced heat and fitted a 'constant running fan' not a moisture control fan or a bathroom fan (very important).
This product if used in the correct way is very good at controlling damp. I ma fully qualified to level 3 in plastering and construction knowledge. We carry out damp proofing and professional plastering using all different specs. We are on tender for a local council and do lots of private work.
We know exactly what we are talking about. Thanks
 
how do i bookmark a thread? im pissed at the minute cos its been a real hard day but.... lets have a go at this sobeer...
 
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