Removing/reducing damp in old buildings
Phil Addison
On Tue, 14 Oct 1997 16:48:56 +0100 in uk.d-i-y James Winspear wrote:
>I am trying to remove/reduce the level of damp in my building (both in
>the structure and therefore in my home). I have a 300 year old house
>which suffers from a multitude of damp-related problems.
[snip]
>The walls have been given a chemical-injected DPC in the 80's and
>re-plastered. Company no longer exists, etc, etc and obviously doesn't
>work.
I injected one of my walls last winter and talked to the chemi-lab of
the manufacturer of the squirty stuff. I was told that the the stuff
is not intended (indeed does not) fill up the pores of the bricks, but
coates the internal surfaces of the pores with a very thin layer which
changes the surface tension so that water does not rise past it. The
upshot of this is that you *can* repeat the treatment if the first
was inadequate. There are other problems with it though, like hard
material the fluid will not penetrate, cracked masonry that vents the
pump pressure so it will not reach right through, and rubble gaps
where it just drains away. Having said that, mine worked OK, but then
i did diy it :-).
>Double-glazing has been partially fitted (reducing
>ventilation/increasing condensation ?)
>Fireplaces have been blocked up (reducing ventilation/increasing
>condensation ?).
>There is no source of penetrating damp, only rising damp.
>
>I have been advised to :
>1. Replace concrete floors with breathable materials : flagstones
>2. Replace modern replastering, with traditional lime based plaster, and
>limewashes
>3. Open up fireplaces, and increase natural ventilation.
>4. Dig a French Drain around the outside of the property
>5. Remove exterior render, and replace with breatheable lime version.
Re 5. I was to chatting to a neighbour who's been renovating his old
house. He's an ex-chemist and talked authoritatively about the
workings of damp, mortar and walls. Anyway he was hacking all the
rendering off his place because, he said, the house was built with
lime mortar which absorbs moisture at certain times and at others
expels it. He said that if the moisture is trapped in the mortar it
will come out on the inside as damp. Sounded plausible to me - let's
see what the experts say.
>If anyone has any thoughts/recommendations I will be very grateful.
--
Phil
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Chris Holmes
The suveyor is going to pay for all this and then live in the resulting
picturesque hovel is he?
I think you need to decide whether you want a museum or a practical house
that you can live in. If the former then return it to it's original
condition, cold wet and smelly. If the latter then take advantage of
modern techniques and materials to keep it warm and dry. I would recommend
having properly installed concrete floors with a DPC and also a proper DPC
in the external walls (remove a few bricks insert barrier, replace bricks,
start again on the next few). My FIL has a 200 year old property and this
is the route he's takeing (having been an Architecheral Technician for 30
years). He's also built an inner skin of breeze blocks. Wouldn't suit
your surveyor I suppose, but then he doesn't have to live in it.
Just my two-pennyworth
andy the pugh
In article <34439467...@imcl.com>, the moving finger of
jwin...@imcl.com wrote...
>
>I am trying to remove/reduce the level of damp in my building (both in
>the structure and therefore in my home). I have a 300 year old house
>which suffers from a multitude of damp-related problems.
>
>bearers/plates.
>The external walls have been covered with an impermeable render
>(pebbledash type).
>The walls have been given a chemical-injected DPC in the 80's and
>re-plastered.
How thick are the walls? If they are anything like my parents house (30"
thick, random rubble, puddled with clay) I doubt if any injected DPC will
have much effect. I would suggest removing the render and repointing with a
lime based pointing, this should allow any water in the walls to evaporate
out, and the pointing should stop it running in in bulk.
For plaster you probably want something which doesn;t soften with damp. I
think (but don;t qoute me on this) tha gypsum plasters satisfy this
requirement, I would suggest you leave the internal plasterwork alone until
it gives trouble, it is a big job, especially if you get a plasterer in
whose professional pride requires him to make up the 1' bow in the walls
etc.
If you do replaster, hand formed radiused edges look far better than edges
made with that metal edging strip, especially in a fundamentally
non-perpendicular house.
Just out of interest, where in the country is your property?
ap
andy the pugh
In article <01bcd951$48482fc0$823d...@netman.sedgehill.lewisham.sch.uk>,
the moving finger of hol...@sedgehill.lewisham.sch.uk wrote...
>
>I think you need to decide whether you want a museum or a practical house
>that you can live in. If the former then return it to it's original
>condition, cold wet and smelly. If the latter then take advantage of
>modern techniques and materials to keep it warm and dry. I would
recommend
>having properly installed concrete floors with a DPC and also a proper DPC
>in the external walls (remove a few bricks insert barrier, replace bricks,
>start again on the next few).
This is all well and good where practical, but less easy with (for
examples) 30" random coursed rubble walls, especially if the bottom few
feet are bedrock as is the case with mny parents house.
> My FIL has a 200 year old property and this
>is the route he's takeing (having been an Architecheral Technician for 30
>years). He's also built an inner skin of breeze blocks.
This is fairly standard, it was suggested that my parents did this, but the
walls were already 25% of the floor area. Another 8" on wall thickness
would have made it nigh on mpossible to even reach the window stays :-)
Their house had a reputation for being the warmest house in the hamlet,
without all these modern developments. To date it is proving cheaper to
heat than their previous house.
I agree with you about floors though (I deleted that line, unfortunately),
if the original poster wants a traditional looking floor I would suggest he
digs out the existing concrete floor, oays a DPC and 2" of foam insulation,
then lays a conctete floor 2" below the current floor level and lays the
flags on top. Otherwise he is likely to get damp seping up through the gaps
in the flags. I see no benefit in a 'breathable' floor.
ap
Phil Addison
On 15 Oct 1997 10:41:06 GMT in uk.d-i-y Chris Holmes wrote:
>I would recommend
>having properly installed concrete floors with a DPC and also a proper DPC
>in the external walls (remove a few bricks insert barrier, replace bricks,
>start again on the next few).
That reminds me... I saw a big old house belonging to a Housing
Association having a dp course put in by a machine that sawed a
horizontal slit all round the base of the walls and inserted a
damp-proof membrane. Not all at once you understand!, but it was a
continuous operation, so the house didn't actually drop a 1/4inch.
Unfortunately the machine wasn't there the day that I was, but I saw
what it had done and it was neat. Apparently they commissioned a firm
to come from London to do it. I *might* be able to get the name from
the HA if anyone wants it. Or does anyone already know what this
system is called?
I tried the diy method Chris Holmes described above and it took me all
day to do a 3' section in a 9" wall. It was very difficult to get the
old bricks out, esp working at ground level. You have to get 3 or 4
out (x2 deep) at a time, then mix up some mortar and put them back in
with a length of dpc underneath. I found it extremely tricky and hard
work. It's a bugger to get the mortar in such a thin slot. By the time
I did this section the mortar had gone off so had to mix a fresh lot
for the next few bricks. Maybe I went wrong somewhere?
I would suggest trying silicone injection where it will 'take', and
only insert the 'plastic' membrane where it won't. Mind you, if you do
put a membrane in, it's the best solution.
For more info on the technique for silicone injection see the thread
around...
Newsgroups: uk.d-i-y
Subject: Re: Chemical Damp Proof Courses & Plastering
Date: Sat, 06 Jul 1996 00:37:28 GMT
Message-ID: <31dda762...@news.demon.co.uk>
Jon Rouse
andy the pugh wrote:
>
> I see no benefit in a 'breathable' floor.
I've discussed this in another thread, but they are warmer and healthier - warmer
because you're not trapping a load of cold water moisture under your floor, and
healthier because the samp is escaping and not feeding all the bugs and mites
that live in damp places. The Victorians knew all about this, but we seem to have
forgotten it lately.
--
The views expressed are my own and may not represent those of my employer.
Please remove the trailing x from the return mail address.
Jon Rouse
James Winspear wrote:
>
> I believe that I'll replaster the internal walls with lime plaster, and
> limewash for the breathing conecpt, unless anyone can suggest otherwise.
No, you're on the right lines there, you can buy lime putty in bags these
days if you don't want a lime pit.
> I am trying to avoid removing the external render and re-lime rendering, if
> possible, as it strikes me that it is something of a double edged sword, in
> that it allows the walls to breathe, but it will absorb the rain water as
> well.
Richardson, the guy who invented Wykamol, has writtena very good book called
(I think) 'Preserving buildings from Damp'. He points out that even in the
heaviest of rain, water is still evaporating from the walls. Only when the
wall is under water does the evaporation stop. He spent much effort working
with paraffin wax, which would form 'hairs' in the pores in the brickwork and
allow water vapour to escape but prevent water droplets from entering. I
don't know if there are 'modern' chemical equivalents.
> I have thought of removing the external render up to about 2 foot (the
> height of a visible extra plinth/thckness externally), and lime rendering
> this. I see no reason to alow the wall to breathe, i.e. allow water in above
> the 770mm height, when there will be no water in the walls otherwise.
You have to be absolutely sure there are no hairline cracks above this level,
or leaking gutters, etc.
> However,
> below this point the rising damp could be 'breathed' out of the walls by the
> lime render. Any thoughts ?
I'm not a fan of render in any of its mainfestations. It just traps moisture
and makes the house colder and damper.
>
> I also intend to dig some form of French Drain which I'm told will relieve some
> of the surface/rainwater ingress into the soil below my house. I have no
> knowledge of how/where/how deep to dig this. Thoughts ?
I've just dug an open 'moat' around the base of my external walls, both
inside and out. It has to be 18in below FFL to work effectively, and
obviously there has to be somewhere for the water to flow to - either a drain
or a soakaway.
Please could you avoid posting much the same information to more than one
thread? Decide which one you are going with, and drop the other.
--
The views expressed are my own and may not represent those of my employer.
Please remove the trailing x from the return mail address.
Skinlaser update at http://www.timewarp.demon.co.uk/sltoday.html
Derek Uttley, Nepean, Canada.
>
> I also intend to dig some form of French Drain which I'm told will relieve some
> of the surface/rainwater ingress into the soil below my house. I have no
> knowledge of how/where/how deep to dig this. Thoughts ?
>
>
> James
The following may not be of any interest but may give some ideas.
Basements are a common feature of houses in Canada. These are usually
built below ground level, so need a means of dealing with moisture. The
"French Drain" that you mentioned sounds like a version of the drainage
tile system used around the base of our basements. Around the external
perimeter of the basement foundations there is a layer of gravel, on top
of which is layed 6 inch diam (approx) plastic corregated tubing. The
tube is perforated to allow water to pour (hopefully drip!) into the
tube at any point along its length. This tube is covered with more
gravel and then the earth. The ends of the tube empty into a sump, which
may drain by gravity (or be pumped) into the storm sewers or drainage
ditch (rural areas). Basement walls are of poured concrete or cinder
block and are coated with a black waterproofing material where they are
covered with earth. The basement floor is concrete over gravel. The
result is a very dry basement.
D.
Simon Pascoe
>
> Richardson, the guy who invented Wykamol, has writtena very good book called
> (I think) 'Preserving buildings from Damp'. He points out that even in the
> heaviest of rain, water is still evaporating from the walls. Only when the
> wall is under water does the evaporation stop. He spent much effort working
> with paraffin wax, which would form 'hairs' in the pores in the brickwork and
> allow water vapour to escape but prevent water droplets from entering. I
> don't know if there are 'modern' chemical equivalents.
>
I believe the Thompson Product 'WaterSeal' claims to allow water vapour
to escape whilst preventing rain water ingress. If it works I think
this clear fluid might help to improve the evaporation and waterproofing
of the James's wall if he decides to remove the external render.
It have recently surveyed a property with a moisture meter which had 18"
rubble walls and no DPC. The meter is able to detect damp through
waterproof render ie :- it will detect if a chemical DPC has failed even
if the wall has been rendered internally with waterproof render. The
meter did not detect any damp around the inglenook fire place which was
'bare brick' . The rendered walls were damp but only to a height of
30cm and because of the render the damp did not damage the decorations.
I believe he reason for such good readings was due to the fact that the
owner had dug an 45 cm deep 'French drain' next to the external wall and
ensured the house had excellent ventilation.
I hope the above helps
Simon
Jon Rouse
Phil Addison wrote:
>
> That reminds me... I saw a big old house belonging to a Housing
> Association having a dp course put in by a machine that sawed a
> horizontal slit all round the base of the walls and inserted a
> damp-proof membrane. Not all at once you understand!, but it was a
> continuous operation, so the house didn't actually drop a 1/4inch.
There used to be a firm based in Telford in Shropshire called Traditional
Damp Coursing, headed by a charismatic character called Bernie the Damp. He
claimed that the building did indeed drop an eigth of an inch after they had
cut a DPC right round, but it was not noticeable.
> Unfortunately the machine wasn't there the day that I was, but I saw
> what it had done and it was neat. Apparently they commissioned a firm
> to come from London to do it. I *might* be able to get the name from
> the HA if anyone wants it. Or does anyone already know what this
> system is called?
A traditional damp course!
> I tried the diy method Chris Holmes described above and it took me all
> day to do a 3' section in a 9" wall. It was very difficult to get the
> old bricks out, esp working at ground level. You have to get 3 or 4
> out (x2 deep) at a time, then mix up some mortar and put them back in
> with a length of dpc underneath. I found it extremely tricky and hard
> work. It's a bugger to get the mortar in such a thin slot. By the time
> I did this section the mortar had gone off so had to mix a fresh lot
> for the next few bricks. Maybe I went wrong somewhere?
I did my solid 14" brick walls (the middle layer at ground level was filled
with wood!). I took out a few bricks, laid the DPC on a dryish bed of mortar
(it skids around if you get the mortar too wet), then laid the bricks on
another dryish bed, with a well buttered upper surface to the brick. If you
make the mortar wedge shaped, pushing the bricks back in forces a little
mortar out, the really tricky bit is keeping the outer face of the brick
vertical.
> I would suggest trying silicone injection where it will 'take', and
> only insert the 'plastic' membrane where it won't. Mind you, if you do
> put a membrane in, it's the best solution.
I have also 'damp-proofed' a rubble filled wall by opening up a
hole at the bottom, letting as much rubble as wanted to fall out,
and then inserting an air brick in each skin. As the wall abutted a step in
the teerrace, and had a constant source of water to one side it was
constantly damp, but this method seemed to dry it out, although it took
nearly a year to completely dry off.
James Winspear
[Also in reply to Phil Addison's message]
andy the pugh wrote:
> In article <34439467...@imcl.com>, the moving finger of
The house, is in Oxfordshire, made 300 years ago, and has walls that comprise
of an exterior course of bricks ( I believe), and then about 12-14 inches of
random rubble (flint, large and small pebbles, earth and followed on the inside
by earth/clay looking daub (?) with a layer of lime plaster on top of that.
Whilst the external bricks could be made to provide some form of DPC
(chemically), the inside main part of the walls definitely do transmit water up
into the walls. The walls also have timber horizontal bearers (?), and up to
about 4 foot high they have all started/completely become
rotten/disintegrated. This rising damp has been increased by the addition of
the concrete floor (I'm told), the addition of impermeable plasters and paints
internally and externally. This has resulted in salt deposition on the walls,
the plaster being rotten (?) i.e. very hollow to the knock, and particularly
easy to come away from the wall itself, as well as the obvious sgins and smells
of damp.
We recently gutted the worst room ourselves (not a job for the faint-hearted,
and worth every penny I spent on good dust masks and goggles). We removed the
offending internal plaster, both the 1982 ish cement and gypsum plaster, which
had been replastered up to about 3-4 feet high to hide the damp, i.e. it was
impermeable, as all chemical DPC companies do. All this did, was to hide for
presumably several years, the fact that the chemically inject DPC had no effect
whatsoever, and had been a waste of money (for this house). We also removed
the lime based plaster above this.
I am stating that the chemical DPC had no effect because throughout this room
and from observation, throughout the house, the plaster is rotten/hollow all
round up to the magic point that water can rise to (about 770mm, I believe),
rather than failing. If the DPC had failed, it would presumably do so, in some
areas, whilst succeeding in others. This is not the case. There is no other
source of ingress of water either, so it must be rising damp.
The reason behind going back to the lime-based breathing concept is that this
house has stood here for 300 years and has survived perfectly well with those
'old' techniques. Along comes the previous owner (a keen 'renovator'), and
listens to the vast majority of the press/documentation surrounding rising
damp, gets in a chemical DPC company, who agree that this is the only way to
solve the problem, injects the walls, replaces the 'deficient' lower plaster,
covering it over with impermable plaster (hiding the problem).
Now comes the crunch, surely no workman would have missed rotten/disintegrating
timbers behind the re-plastered area? They must have been there for about 285
years, and were persumably OK at the time of replastering. 3 years ago, I
bought the house, believing the 2 surveys I have done, both saying that a
simple chemical DPC will resolve some 'minor' rising damp. After having 7
'Damp' companies come round and several more independant surveys, all saying
chemically inject, I listened to a work colleague, who suggested I contact the
Society for the Protection of Ancient Buildings (SPAB), whose documentation
draws me round to this 'breathing' concept. When we removed the offending
'new' plaster, all the timbers hidden behind were in varying states of
disintegration. Some had completely 'crumbled' literally into fine damp
flakes, some leaving a rather large worrying gap where they should be helping
to support the wall! The timber beams above the magic 770mm mark, i.e. above
the rising damp were all perfectly OK, all showing the original saw and adze
marks of 300 year old wood. This must show that the changes in the house
recently (concrete floors, impermeable external/internal plaster/renders) have
been as a marked detriment, and have rapidly increased the rotting of the wood
etc.
I agree with Andy that internal rounding of corners is preferable, and I may
well attempt to do the plastering myself, as making the walls flat is not the
intention, and the rough contouring look would be more in keeping with the rest
of the house - the traditional country cottage look.
I believe that I'll replaster the internal walls with lime plaster, and
limewash for the breathing conecpt, unless anyone can suggest otherwise.
I am trying to avoid removing the external render and re-lime rendering, if
possible, as it strikes me that it is something of a double edged sword, in
that it allows the walls to breathe, but it will absorb the rain water as
well. I have thought of removing the external render up to about 2 foot (the
height of a visible extra plinth/thckness externally), and lime rendering
this. I see no reason to alow the wall to breathe, i.e. allow water in above
the 770mm height, when there will be no water in the walls otherwise. However,
below this point the rising damp could be 'breathed' out of the walls by the
lime render. Any thoughts ?
I also intend to dig some form of French Drain which I'm told will relieve some
Derek Tidman
In article <3445DF...@postoffice.co.ukx>
rou...@postoffice.co.ukx "Jon Rouse" writes:
:-I have also 'damp-proofed' a rubble filled wall by opening up a
:-hole at the bottom, letting as much rubble as wanted to fall out,
:-and then inserting an air brick in each skin. As the wall abutted a step in
:-the teerrace, and had a constant source of water to one side it was
:-constantly damp, but this method seemed to dry it out, although it took
:-nearly a year to completely dry off.
:-
I would strongly suggest that this is the most effective way
of dealing with the problem. In fact Doulton (?) market a
damproof system that inserts ceramic pipes into the wall. These
pipes have a ventilated end cap that allows the air to dry out
any water that gets drawn through the pipe. I would imagine
that the caps do no more than make it tidy and stop the noise
caused by the wind. Traditional terracotta air bricks may well
be as effective as they should also draw water.
--
DT