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Default New damp proofing failed - replastering help needed

Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and
have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast
before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall. We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)
I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house. Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.

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Default New damp proofing failed - replastering help needed

Mike wrote:

Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and
have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast
before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall. We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)
I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house. Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.


I recommend you do some reading first. The problem needs to be
understood more clearly if its to be solved.
http://periodpropertyshop.co.uk/phpB...wforum.php?f=1


NT

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Default New damp proofing failed - replastering help needed

On 2 Sep, 11:38, Mike wrote:
Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and
have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast
before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall. We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)
I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house. Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.


The sand cement render would contain a proprietory damp/waterproofer
and form a containment barrier. As long as this containment also
crosses the chemical dpc it "works"
Exactly why the numpty didn't use the same technique in the problem
areas is beyond me.
Your idea is exactly right as to the way to deal with the problem. It
is possible that the new dpc is now exacerbating the original problem
as the damp is now rising in a concentrated area.
Regarding the preparation, chip away any old render or plaster as this
will wick the moisture upwards past the dpc if left in place. (I
assume he "did" put a dpc in the problem area???)
It should be perfectly fine to get adhesion to freshly chipped
surfaces without using pva or other adhesives. Sand and cement form a
perfectly good adhesion to brickwork as you can see by a properly
built brick wall! Don't forget to use waterproofer in the render mix.
If there is a problem with getting a starting adhesion "spatter" the
wall with mortar and let it dry (and stick) then use this as a key for
your render coat.

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Default New damp proofing failed - replastering help needed

Mike wrote:
Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and
have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast
before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall. We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)


My guess is yo are wroing, and the chimney isn't properly proofed, and
never could be,which is why he used plasterboard, knowing it would last
long ENOUGH before you noticed and stopped the cheque.

I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house. Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.


If this is an *outside* single brick wall, then this may work..rising or
penetrating damp can escape outwards and as long as you waterproof
rendering goes up high enough, it will have gone before it gets inside.

What worries me is the word 'chimney' - is it capped/vented? It may be
rain coming *down* the chimney, in which case you may bed up sealing it
in...
Another solution for outside walls is to stick up a vapour barrier (poly
sheet) and studwork with insulation and dry line with foil backed board.
As long as the timber is away from the wet walls, it won't rot, as long
as the walls are not waterproofed OUTSIDE to prevent them breathing.
Actually it will still work then,. but rising damp plus frost may make a
nonsense of the bricks..
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Default New damp proofing failed - replastering help needed

wrote:
Mike wrote:

Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and
have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast
before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall. We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)
I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house. Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.


I recommend you do some reading first. The problem needs to be
understood more clearly if its to be solved.
http://periodpropertyshop.co.uk/phpB...wforum.php?f=1


Indeed, but that side understand it even less..

So do the reading elsewhere.


NT



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Default New damp proofing failed - replastering help needed

In article . com,
Mike writes:
Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and


Chances are it wasn't rising damp (almost never is),
so it's not surprising that it didn't cure the problem.

have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast


Yes, sand/cement/waterproofer scratch coat is a good barrier
against penetrating damp, so it looks like you may have had that.
You should also investigate the cause of the penetrating damp and
try and fix that. If moisture is getting in to the outside of the
wall, it will deteriorate.

before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall.


Was the fireplace damp when you opened it? They often are.
If so, this should have been left opened and ventilated for
a few months to allow the brickwork to dry, before applying
any finish.

We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)
I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house.


Yes. But when you've stripped it back, leave it for as long
as possible to allow the brickwork to dry. Also, you need to
investigate why you have penetrating damp -- what's on the
other side of the wall?

Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.


PVA the brickwork with watered-down PVA. If the brickwork is very
absorbant, do two coats, allowing first coat to dry, but do the
final coat just before you start putting on the scratch coat plaster
so it's not completely dry.

A good scratch coat mix is 1:1:6 cement:lime:sand. Add a mortar
waterproofer to the water (or a combined plasticiser/waterproofer).
Make sure any metal edging strips you use are a type which won't
rust (same for any nails which hold them in place temporarily).
Devil-float (score) the surface of the scratch coat when it all
on and flat to give more key for the finish coat.

Use standard multi-finish gypsom plaster for the finish coat.
Apply 24-48 hours after the scratch coat, whilst it's still damp,
without using any PVA. If you leave it longer and the scratch
coat dries, you need to plaster as for a reskim, which means
PVA'ing the wall first. Do not allow the finish coat to bridge
the waterproof scratch coat layer anywhere, as it will wick
moisture through.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
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Default New damp proofing failed - replastering help needed

Andrew Gabriel wrote:
In article . com,
Mike writes:
Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and


Chances are it wasn't rising damp (almost never is),
so it's not surprising that it didn't cure the problem.

If its a property pre 1900, with no DPC at all, chances are that it
almost always IS rising damp, for which injection is an excellent remedy.


Post the period, your statement is largely correct.
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Default New damp proofing failed - replastering help needed

On 2 Sep, 11:38, Mike wrote:
Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and
have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast
before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall. We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)
I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house. Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.



Dear Mike
You were right to put the "Pro" in inverted commas as he most
certainly was not what is implied by the term!
The most sensible reading you can do is on the BRE documentation. Some
websites are quite good and you could try that of RTS on
http://www.buildingpreservation.com/
The Period Property one is reasonable in its technical content but you
may get a bit lost in the purist parts some of which may not be
apposite for your problem.
As I understand it and I am happy to be corrected you have dampness
that might be on of three possible sources
a) rising
b) hygroscopic due to the burning of fossil fuels (SO2 to SO3 to
sulphurous acid to sulpuric and then sulphates)
c) lateral penetration
My guess is that it is likely to be a mixture of a and c
First
Check the external ground levels and make sure the existing dpc (it
has been part of building regs since 1886) is 150mm above ground
levels and lower ground if needed
Second
Get rid of any plasterboard and dabs which will be gypsum-based and a
direct coduit of damp and hygroscopic salts in the wall
Rake out any mortar 20 mm internally
check that the dpc has been injected in the correct location AND in
the mortar not brick
See the BS on this or the PCA (ex BWPDA) Code of Practice as to how
and where to inject a chemical dpc
If not - RE inject the mortar (I suggest it is easy to DIY with Dry
Zone from Safeguard Chemical
You can easily do this yourself
Then
replaster in a sand cement render 3 to 1 with a silicatious rather
than hydrophobic water "proofer" - I suggest SIKA No 1
Two (thin?) layers of render followed by a thin finish coat of multi
finish will do the trick
Try to overlap with his existing render by angle grinding a half lap
join and using Feb SBR glue to effect the join
Any questions - feel free to come back
If you were to send a photo I could be more specific
Chris George

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Default New damp proofing failed - replastering help needed

Hi, Thanks for all the help so far. Most of my questions answered but
should have given a bit more info in the first place:

1870s terrace with no existing DPC. Pretty convinced myself that
original problem was rising damp because the bottom 2-3 feet of all
downstairs walls were visably wet with plaster falling off, rotten
skirtings, doorframes etc and no damp problems anywhere else in the
house. Also all areas where cement mix was used are now fine, only
plasterboard areas affected ( and this included a piece of board right
in the middle of a wall which is fine apart from the boarded section.
The problem chimney breast has had DPC injected. Also, our other
chimney breast which board was not used on is fine. I'm still feeling
that the plasterboard is the problem here and just wasn't suitable for
the job.
No idea why job was done in this way but suspect it may have been
because they had used all the sand they had or that side-kick who did
the boarding wasn't able to do plastering.
Anyway, it would make sense to me to try and match the mix for new
plaster to the areas already done. I'm sure that only sand, cement and
liquid dampproofer was used, so i'm after a ratio of sand (builders?)
to cement and a recommendation for which dampproofer to go for. not
much plastering experience so any general tips would be helpful.
Thanks again

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Default New damp proofing failed - replastering help needed

Sorry Chris, Posted last effort before reading yours. Have read some
of the suggested stuff before and my guess would have been option B,
because there is no damp in any direction around the problem areas,
the DPC appears to have been done properly, internal wall, problem is
all over where dabs are rather than just bottom couple of feet, and
salt crystals are clearly to be seen on the damp patches. The chimney
was very sooty and damp when opened up and probably not given long
enough to dry out so i'm thinking dabs have leeched salts into board
which now suck in moisture on wet days. Does that sound plausable?
If the cure is the same i guess the cause doesn't matter so much - if
proposed replastering will sort the problem either way? Cheers



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Default New damp proofing failed - replastering help needed

On Sep 2, 11:38 am, Mike wrote:
Hi
Long story but i'll try to not to go on for ever!. We had a 'pro' in
who injected DPC and re - plastered bottom metre or so of our ground
floor to solve rising damp. 6 months on we still have some damp and
have now given up on trying to get hold of the guy that did the work.
This is our first house and we simply cannot afford to pay anyone else
so need a DIY fix.
To be fair the job is not an entire disaster as it has worked in areas
where cement / sand undercoat was used. We opened up a chimney breast
before dampwork was done (to about 6 feet for a cooker) and for some
reason the guy has used plasterboard in this area plus in one other
small area of wall. We now appear to have penetrating damp in these
plasterboarded areas. you can clearly see damp circles where the dabs
are holding the plasterboard to the wall which get noticably worse on
wet days and salt crystals have formed on the surface of these
patches.
My guess is that the DPC is fine and the plasterboard is 100% the
problem (i know chimney breasts are problem areas but the other area
of plasterborded normal wall has the same problem and either side of
it is fine)
I'm guessing i need to rip out the plasterboard and re plaster as per
the rest of the house. Looking for a blow by blow run down of how to
do this, in particular how to treat / prime the brickwork, ratio of
mix for the undercoat and which damp proofing additives to use in the
mix (also not sure if i need to use additives in the skim coat?
Thanks to anyone who got through that lot and any advice will be much
appreciated.


Have you checked if your cavity (if you have one) is full of stuff ?
Take a brick out, and have a look. Its an simple, but time consuming
job to clean it out.

I am using a render, with Sika-1 to damproof my cottage, its easy to
do - the materials are not cheep. There are alternative render
additives, if you are above ground level.

Rick

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Default New damp proofing failed - replastering help needed

The Natural Philosopher wrote:

Chances are it wasn't rising damp (almost never is),
so it's not surprising that it didn't cure the problem.

If its a property pre 1900, with no DPC at all, chances are that it
almost always IS rising damp, for which injection is an excellent remedy.


Many places of that age (and earlier) will have had a slate DPC, which
is usually very effective. Much depends on the area of the country and
the style of construction.

IME, rising damp comes after a long list of more probable causes.

Penetrating damp from splashback against the wall over the existing DPC
is more common in solid wall properties of that age, and there are
plenty of other things to check (pointing, rainwater goods, ground level
outside, airbrick obstruction etc).

--
Cheers,

John.

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