How to stop a patch of bubbling paint
swinster
I have recently had basement renovation with most wall having dot/dab
plasterboard, apart from a couple of cheeks of an alcove that were
plastered direct on the brickwork. On one of these cheeks the paint
bubbles an falls off in a smallish area (approximately 30cm sq). I
have painted the area a few time now but after a couple of months tha
paint starts bubbling, and eventually I will need to scrape off all
the paint in the area.
Is there anything that might be causing this and anything I can do to
stop it?
Tabby
damp. and no, if damp's coming through a basement wall there's nothing
that will stop it. Suggest redoing that bit in dot & dab, then the
damp can evaporate away.
NT
swinster
>
> damp. and no, if damp's coming through a basement wall there's nothing
> that will stop it. Suggest redoing that bit in dot & dab, then the
> damp can evaporate away.
>
> NT
I don't think its damp. The "basement" is actually at ground level at
the rear of the house, the alcove is part of an internal wall
(terraced house), and the problem is actually on the cheek of the
alcove. The alcove is created from the chimney breast, so unless damp
is coming in from the very top (4 floors away), I just can't see it
being damp. The patch that is bubbling is around 5-6 ft from the floor
(about a foot below the ceiling), and there is no problem either above
of below this patch or on the other cheek. The plaster underneath
doesn't appear to be damp - there is no tell tale dark patch -
however, is there anyway to tell for sure?
Further info. I painted the plaster with a 50/50 mist coat emulsion,
then when dry with an acrylic eggshell (water based). However, there
must be an issue with this particular area as this is the second time
it has happened.
swinster
> damp can evaporate away.
PS. this area is actually plaster on brick - the rest of the basement
in dot/dab. I had to remove the dot/dab on both cheeks to give myself
just enough room to fit a range cooker between the cheeks in the
alcove.
Tabby
oh I see, I though this was underground external wall. For want of a
clearer direction I'd strip any that will come off and redo it
properly, 1:5 pva first, then emulsion and only emulsion. Piss coats
result in much of the glue in the paint migrating into the plaster,
much weakening their hold. And I'm not 100% certain how reliable
acrylic on emulsion is. I dont know if looking inside a bubble might
tell you which layer is detaching.
NT
swinster
> oh I see, I though this was underground external wall. For want of a
> clearer direction I'd strip any that will come off and redo it
> properly, 1:5 pva first, then emulsion and only emulsion. Piss coats
> result in much of the glue in the paint migrating into the plaster,
> much weakening their hold. And I'm not 100% certain how reliable
> acrylic on emulsion is. I dont know if looking inside a bubble might
> tell you which layer is detaching.
>
> NT
Cheers. I thought I had PVAed first originally, but I might be mixing
it up with another wall!!
I did check with the supplier about the compatibility prior to
application. I was told that as both paints (emulsion and acrylic)
were water based, there would be no issue. Indeed, in the rest of the
place the paint as gone on very nicely.
I do need to scrap off some more paint in the next couple of days
(after Christmas has died down) so I will check the bubbles, but I'm
pretty sure the paint is peeling from the very base layer to the
plaster - when it all comes off the plaster is showing and its not as
though I'm trying that hard to scrape off the paint to the plaster.
Tabby
Sounds like the piss coat failed.
NT
Tabby
The Natural Philosopher
damp.
let me guess, its an old chimney breast?
My old house was permanently like that.
Only remedy is to somehow either stop the damp getting in - a ticklish
project - or strip the plaster and render with string mortar - 50-50
sand/cement - and then replaster. That will drive the damp to hopefully
the inside of the chimney where the flue can evaporate it.
Or you MIGHT be able to get away with a DP injection into the brickwork
itself.
Followed by replastering etc.
The Natural Philosopher
> On 26 Dec, 16:25, Tabby <meow2...@care2.com> wrote:
>> damp. and no, if damp's coming through a basement wall there's nothing
>> that will stop it. Suggest redoing that bit in dot & dab, then the
>> damp can evaporate away.
>>
>> NT
>
> I don't think its damp. The "basement" is actually at ground level at
> the rear of the house, the alcove is part of an internal wall
> (terraced house), and the problem is actually on the cheek of the
> alcove. The alcove is created from the chimney breast, so unless damp
> is coming in from the very top (4 floors away), I just can't see it
> being damp.
well look again
Its either rain coming down the chimney, or if its low..below a ft above
ground level - its damp rising through the stack. from the ground. Most
chimney stacks were never damp proofed. The fire in them would keep the
things dry enough.
The patch that is bubbling is around 5-6 ft from the floor
> (about a foot below the ceiling), and there is no problem either above
> of below this patch or on the other cheek. The plaster underneath
> doesn't appear to be damp - there is no tell tale dark patch -
> however, is there anyway to tell for sure?
meter maybe, but this looks more promising. At that height its likely to
be rain ingress into the stack - there's probably a brick ridge inside
that collects water or something.
>
> Further info. I painted the plaster with a 50/50 mist coat emulsion,
> then when dry with an acrylic eggshell (water based). However, there
> must be an issue with this particular area as this is the second time
> it has happened.
strip the plaster round that area - for at least 6" every way and apply
a strong mortar direct to the brick, then replaster it.
swinster
check.
I should also be able to access the top of the brickwork of cheek of
the chimney breast (just above the ceiling of the area that's
bubbling) as we still have a big hole in the floor above where the
old hearth was knocked out, and a hole in the ceiling in the middle of
the alcove where the a new kitchen hood extracts to.
All a bit difficult to explain without photos.
Tabby
> Cheers. I think I will hire out a damp meeter for a day just to double
> check.
I think that would be pointless. The measure of whether you have a
damp problem is not the measure of water content plus other causes of
conductivity, but simply looking at whether you have the signs of a
damp problem. Damp and damp problem are 2 different things, old houses
routinely have some damp plus greater conductivity. Also you've just
put plaster and paint up, so the cause and possible permanentness of
any damp would be unknown, making the readings of little use.
You already know the piss coat failed, and that much of the glue in it
was washed out on application.
TNP's advice is contrary to that given by the experts. Check out what
SPAB says about cement on old brickwork.
NT
swinster
. Check out what
> SPAB says about cement on old brickwork.
>
technical-qa-1-dealing-with-inappropriate-cement-renders/" ?
I realise that these comments are outlined in relation to old/historic
buildings, and whilst our house is quite old, it still only dates to
the 20th Century (1914 ish). Our house (along with most terraced
houses round here) are rendered externally with, I assume, cement
renders and pebble dash. Interesting comments nevertheless, but I'm
not sure how relevant they are to this situation.
The Natural Philosopher
No it is not
Its just against certain stupid people who think that the cases of very
old brickwork built out of lime mortar and with inadequate damp proof
courses are universally applicable.
Waterproof mortar tanking is a well known technique used in many
victorian/edwardian properities to good effects.
A si brick injection below normal DPC.
Check out what
> SPAB says about cement on old brickwork.
>
Check out what SPAB has to say on global warming and teh keeping of bees.
It has as much relevance.
>
> NT
The Natural Philosopher
modern houses and those built before 1700. Out of damp crumbly brick and
lime mortar.
The fact that Portland Cement and fairly hard brick have been about
since the turn of the century, passes him by completely.
Tabby
Theyre relevant to buildings of soft brick and shallow foundations.
Comments but no substance from tnp I see.
NT
The Natural Philosopher
which this is not
> Comments but no substance from tnp I see.
>
No, that's you dear.
>
> NT
Tabby
wrote:
If you have any expert reference that explains the issues SPAB et al
raise regarding cement on soft brick with shallow foundations, feel
free to link to it.
NT
The Natural Philosopher
Why do you persist in waffling on about this, when it has nothing to do
with the original question.
What about the above do
p yopu utterly fail to understand?
>
> NT
Tabby
didnt really think you had anyting
The Natural Philosopher
> On Dec 29, 7:44 pm, The Natural Philosopher <t...@invalid.invalid>
> wrote:
>> Tabby wrote:
>>> On Dec 29, 2:05 am, The Natural Philosopher <t...@invalid.invalid>
>>> If you have any expert reference that explains the issues SPAB et al
>>> raise regarding cement on soft brick with shallow foundations, feel
>>> free to link to it.
>> Why do you persist in waffling on about this, when it has nothing to do
>> with the original question.
>>
>> What about the above do
>> p yopu utterly fail to understand?
>>
>>
>>
>>> NT
>
> didnt really think you had anyting
Dear tabby, when I am answering a question about apples, why do you
persist in claiming I know nothing about oranges.
And then attempting to to insult our intelligence by saying 'there, he
hasn't got an answer'
Do you really think that anyone with 10% of a brain, or more, cannot
see how stupid that makes you look?
geraldthehamster
>
> - Show quoted text -
I've been resisting, and I know I'll regret this, but...
I'm still wrestling with
>You already know the piss coat failed, and that much of the glue in it
>was washed out on application.
Is there something esoteric here that I'm missing, or is the poster
suggesting using PVA as a mist coat? Because if anything is almost
guaranteed to make it hard for paint to stick, it's a nice coat of
PVA.
Cheers
Richard
Tabby
geraldthehamster
>
> - Show quoted text -
I know that, I didn't pick up a paint brush yesterday. I've just no
idea what you mean by glue, unless you're referring to co-polymer
binders.
Cheers
Richard
Tabby
emulsion contains a glue, and piss coating results in a fair bit of it
soaking into the substrate rather than binding the paint layer. I'm
not clear what is unclear.
NT
geraldthehamster
Emulsion doesn't contain a glue, unless you're referring to copolymer
binders, or using something like vinyl silk, which isn't much good for
a mist coat. What was unclear was your use of the term "glue", and
your earlier assertion that the OP should use PVA before painting.
Doesn't matter anyway.
Cheers
Richard
Tabby
A binder is a glue, its what sticks the paint film together. PVA is
fine before painting if the surface needs it as long as its not
overdone and it soaks in - a slick surface would of course be a
problem
NT
geraldthehamster
Disagree concerning PVA before paint.
Cheers
Richard
swinster
manages to actually get on to this problem. I have remove the cooker
hood and taken some photos of both the wall and above the ceiling in
the cavity. Not sure if this will shine any further light on the best
way forward. or not
The photos are at:
http://www.flickr.com/photos/swin70/sets/72157625745292126/
You can see the patch roughly where the bubbling started. I drilled a
couple of holes in the wall to indicate where the problem was most
acute. The rest of the paint I have striped myself.
The cavity shot is take from above the ceiling, just inside the cooker
hood opening (as can be seen top left in the above photo). There is
not much brick work directly above this cheek of the chimney breast,
in fact its just a void. You can see some cured expanding foam which
basically indicates where the ceiling meets the chimney breast cheek
and has been plastered from bellow. I'm not sure if you can see a
small dark patch to the left of the expanding foam at the bottom of
the chimney breast cheek brick - this is almost directly above the
holes drilled as seen in the previous picture. Sticking my finger in
there, it does smell kinda musty, but I can see no further evidence of
moisture either above or behind this area, or under the concrete
lintel (left). Also, it has been raining constantly for the past two
days.
Could this be residue moisture somehow trapped? If so what to do? Any
ideas?
swinster
>
> The cavity shot is take from above the ceiling, just inside the cooker
> hood opening (as can be seen top left in the above photo). There is
> not much brick work directly above this cheek of the chimney breast,
> in fact its just a void.
>
>
is on the other side to where the problem is (where the cooker hood
extracts to - right, not left). The area above the void in the photo
(but out of sight) is solid brick.
swinster
Ok, I cut some of the expanding foam off and plaster the area in the
void with cement. I might stick some insulation up there for good
measure.
I don't see what else i can do so have just scratched the plaster and
filled over the top. I will try a new coat of emulsion and see how we
go.