1848 Brick House Damp

[supermattt]

Hello All,

I posted this on the old board without relising it was the old board. This board seems busier so I have reposted here:

I've bought a ground floor flat in a row of 'Silkweavers Cottages'. There is a damp issue which I knew of when I bought it, and which I am now trying, by a process of elimination, to solve.

The main symptom is in the kitchen where there is blistering of the paint and plaster on an interior wall. I have pulled away the plaster where it is loose, and it appears the finishing plaster is set on top of mortar (hard, grey looks a bit like concrete), and then I assume under that, Brick. Non of the mortar is crumbling. The blistering starts above the skirting board which is sound, no rot or softness.

The back wall of the house, inside of which is the bathroom, also displays similar symptoms, though it seems quite obvious that this is from a leaking window sill. The first time it rained when I was in the flat I noticed the guttering under the roof at the back was broken and water was more or less pouring onto the window area. The sill is parlty rotten.

So, I have had the guttering fixed and am planning to dig out the portion of the wooden sill that is rotten and fill it with some waterproof exterior filler substance (any suggestions?). I am hoping this will deal with the back wall.

Where I need help then, apart from any practical advice anyone has, is in dignosing the more elusive cause of the Kitchen wall. There are damp patches in other parts of the house also, all near the floor, 2 of them near/ around electrical sockets (the channels for which I thought may be conduits).

The Floor throughout as far as I can tell is concrete and is covered in laminate wood flooring. There is a vent through a front living room wall to outside which amounts to a hole in the wall and there is an uncovered fire place which I suppose also amounts to a hole in the ceiling....things I guess might be contributing.

I have taken some of the plaster off in the kitchen and the wall is not damp underneath though there is some salty deposit.

Can anyone recommend a good step by step elimination-of-causes-one-by-one type book that I might be able to purchase?

My current proposed strategy is to replaster the wall in the kitchen with something breathable (lime plaster?) and see if stays.

Any thoughts, hints, advice or comments very gratefully received.

With many thanks
Matt

 

[biffvernon]

Sounds like you are doing the right things.

Stop more water getting in by fixing gutters and window sills (theres are some resins you can repair rotten wood with)

Hack off as much of the cement render as you can and replace with lime plaster. Paint with very breathable paint (see Rose of Jericho)

Much of the damp is probably condensation. Keep the room well ventilated especially when cooking, washing and breathing.

What is a silkweavers cottage?

 

[supermattt]

Thanks Biff.

Any ideas about the damp around the power sockets. Whereas the wall in the kitchen is dry, in two places the area around power sockets actually feels damp. I understand that a channel would have been cut in the brick to house the wires..can these act as a conduit in some way?

Any suggestions for the type of thing I might use to fill the slightly rotten sill...'resin filler'?

Thanks again
Matt

 

[biffvernon]

Ah. The say a bit a of damp makes the electricity flow more easily.
Hard to know without seeing it. Maybe the channels are just a tad colder than the surrounding sruface so attract the condensation?

 

[Paul Hopper]

Biff has good points. there certainly will never have been any serious attempt at an original damp course on the ground floor,Wiring in metal conduit and with metal back boxes will certainly attract condensation and the area surrounding will feel damp.try keeping the house at as even a temperature as you can (a tall order in UK I know!) monitor over a period of time and in different weather conditions also when cooking, ironing,showering or using the bath, if the moisture level is relatively constant,you probably are suffering general condensation, Look to the outside brickwork and mortar courses particularly,if the bricks are spalling (breaking up) or the mortar seems soft and friable then an external moisture source seems likely.Do you know if anyone has "had a go at it " at any time? After all these years the original olaster sand/lime may have begun to become hygroscopic ( like the salt or sugar if you leave it out in a damp atmosphere.)Also I suspect maybe some re plastering may have been carried out where the power boxes were fixed. If this was a few years ago the plaster used could have had a soft (Browning) backing. This is notorious in my experience, for remaining damp or attracting moisture. Take a sample to see of it is wet behind or at theside of the power sockets (mind the wirea!) If the sample seems fairly dry and dense then surface condendation may be the cause.Older houses especially where you are, were very much vernacular architecture built as cheaply as possible to house the workers and not much thought was put into their durability,we have some visually beautiful cottages in our local town, built for a similar purpose but sadly just not up to 150 or more years of living in without some quite major works.How substantial is the building?some mid 1800's properties were very soundly built but so may others were not, compare yours to others nearby, ask owners of simliar properties what problems they either have or have had, this may help you develop a strategy.
good luck! keep us posted..
Paul

 

[supermattt]

Paul and Biff,

Thanks bery much for your very useful replies. I've been off in the South of France so apologies for long pause.

I will be having another think about what to do next this weekend so no doubt will have some more questions/a strategy.

Thanks again, much appreciated.

Matt

 

[supermattt]

Thanks Biffvernon,

So just powdered limestone and water? Where do I get limestone?

“Hack off as much of the cement render as you can and replace with lime plaster” Is the cement render the grey stuff under the pinkish plaster? Will there be bricks under that and should I take the cement render off even if it is quite sound and solid? There are small crystalline deposits on the surface of the cement, does this indicate anything? There seems in the kitchen to be a thin (1mm) layer of something very dark grey. Any idea what this might be?

Paul:
“I suspect maybe some re plastering may have been carried out where the power boxes were fixed. If this was a few years ago the plaster used could have had a soft (Browning) backing.” I’ve scraped away around one of the sockets. The wires are housed in a plastic tube set in a groove that is filled over with fine white plaster. It doesn’t seem particularly damp. The back box is plastic and it looks like there is some grey concrete render around it also.

So my current my current strategy is to take off any paint and plaster that will easily come away from the walls and then take as much of the concrete render off as I can under that down to the brick. Then re plaster with lime plaster and finish with breathable paint.

Does this sound reasonable?

 

[biffvernon]

So my current strategy is to take off any paint and plaster that will easily come away from the walls and then take as much of the concrete render off as I can under that down to the brick. Then re plaster with lime plaster and finish with breathable paint.

That's exactly what I've done on my house where I found soemthing similar to what you've described. The more cement you remove the better but there comes a point when it's too much like hard work. I've lime plastered over obstinate areas and it seems to have worked.

 

[GK]

Yep, sometimes it's less damaging to the building to just leave it, which is what I did here. The pink and dark grey bit is render, the scratched bit is base coat lime. The ridiculously hard cement with gypsum over was gouged out with an angle grinder for a key and the whole lot lime plastered over. This internal wall was always damp, so far it seems to have done the trick

 

[NT]

Thanks Biffvernon,

So just powdered limestone and water? Where do I get limestone?

“Hack off as much of the cement render as you can and replace with lime plaster” Is the cement render the grey stuff under the pinkish plaster? Will there be bricks under that and should I take the cement render off even if it is quite sound and solid? There are small crystalline deposits on the surface of the cement, does this indicate anything? There seems in the kitchen to be a thin (1mm) layer of something very dark grey. Any idea what this might be?

Paul:
“I suspect maybe some re plastering may have been carried out where the power boxes were fixed. If this was a few years ago the plaster used could have had a soft (Browning) backing.” I’ve scraped away around one of the sockets. The wires are housed in a plastic tube set in a groove that is filled over with fine white plaster. It doesn’t seem particularly damp. The back box is plastic and it looks like there is some grey concrete render around it also.

So my current my current strategy is to take off any paint and plaster that will easily come away from the walls and then take as much of the concrete render off as I can under that down to the brick. Then re plaster with lime plaster and finish with breathable paint.

Does this sound reasonable?

And giving the brickwork time to dry out would certainly help. But really I'd address the biggest causes of damp before any of this. Ie water pouring onto walls, exterior ground level not being well below floor level, leaks and so on.


NT

 

[Matt Green]

If the internal plaster is cement based, it will be holding back water within the masonry. The water is going to move to areas where it can evaporate, either over the top of the plaster or through seams/joins or areas where the plaster is thinner- like where conduits have been buried.

I wouldn't worry too much about water condensing on the metal, the reduced thickness of the plaster is a more likely cause. Stripping it and replacing it with something breathable seems a very good idea. Have you checked the exterior ground levels are ok?


Matt Green

 

[supermattt]

Thanks everyone,

External ground levels are ok and I've fixed a gutter that was causing water to pour onto an external wall. The exterior pointing seems ok thought ther is a bricked up fireplace about which I know very little, when, how etc. I wil have more of a look around when it next rains though.

Thanks
Matt

 

[NT]

Sounds like youve solved the mains problem, but it will take quite a while to dry out. Re cement, I'd only remove what comes off without causing damage.


NT

 

[supermattt]

OK thanks NT

 

[supermattt]

The concrete seems quite thick down to the brick, about 2cm and is mostly very hard so I'm not going to try too hard to get that off. There is a definite thin layer of dark grey between the concrete render and the pink plaster. Does nayone know what this is? Would it be some sort of damproofing? I'm trying to at least get down to the concrete render in the affected area and then I am going to replaster with lime plaster.

Thanks for any hints & tips

Matt