Damp walls in old house

[eoinm]

I'm getting work done on an old (~100yrs) house. Since the house was renovated about 10 yrs ago there have been increasingly large yellowish / brown damp patches on the bedroom walls (1 wall in each room, mainly where the chimney was covered, some ingress on the cieling and onto side walls).

From reading, these appear to be caused by the hygroscopic salts in the old chimney. As it's a holiday home it can be left for months unheated, unventilated and so was a prime damp magnet. We are now doing it up for rental, installing central heating, ventilation etc. so those issues should be removed.

I have stripped the walls back to the bare brick and am leaving for a while to dry out any moisture in the walls (althought maybe this is a waste as I'm sure the salts will keep attracting the moisture).

In any case I've been told by builders this is rising damp despite being present on the second floor and nothing at all being evident until about 3 feet up the wall. It's also just patchy descolouration, not flaking, no mould. See the photo below.



After stripping back.


What's the best way for me to make sure this won't continue once it's re-plastered? Some sort of mesh membrane?

 

[johniosaif]

The builder is wrong , rising damp starts from the ground. Possible penetrating damp but unlikely from info received.Salts are often in old chimneys, you can plaster them using sand /cement with salt inhibitors or cement based plasters like Dri-coat or renovating plaster, you can also dry line by fixing tanalised battens to the wall, levelling same and fitting foill back plasterboard and then skimming or taping, you could also as an alternative fit plastic membrane for plastering which keeps all damp and salts about, google any of these terms for more info.. Best of luck

 

[keithuk]

I think John have covered this one ,the only thing i may add is ,make sure the plasterer board to the left in the picture ,does not touch the wet wall ,as it does seem to be bridging across showing damp ,best of luck with it

 

[S a plastering]

If that is an old chimney it needs venting it's more a condensation problem with moist air getting trapped

 

[eoinm]

Hi, thanks for all replies, good info in them. Regarding being an old chimney yes it is, as old as the house and used for years with fossil fuels. It's been capped but not vented as far as I know. How do you vent it (aside from the obvious answer of 'add a vent!')? Is this vented into the room or a vent outside?
THanks.

 

[eoinm]

I think John have covered this one ,the only thing i may add is ,make sure the plasterer board to the left in the picture ,does not touch the wet wall ,as it does seem to be bridging across showing damp ,best of luck with it

Thanks for the info. Regarding stopping bridging - if I get it replastered with some / all of the options that John mentioned would it then be ok for the board on the left to touch?

 

[eoinm]

The builder is wrong , rising damp starts from the ground. Possible penetrating damp but unlikely from info received.Salts are often in old chimneys, you can plaster them using sand /cement with salt inhibitors or cement based plasters like Dri-coat or renovating plaster, you can also dry line by fixing tanalised battens to the wall, levelling same and fitting foill back plasterboard and then skimming or taping, you could also as an alternative fit plastic membrane for plastering which keeps all damp and salts about, google any of these terms for more info.. Best of luck

Thanks for the reply and info. If I wanted to be 110% certain about stopping this reoccurring what combination of what you mention would you recommend? Is the plastic membrane option expensive or a specialist installation?

 

[bubbles65]

Hi, thanks for all replies, good info in them. Regarding being an old chimney yes it is, as old as the house and used for years with fossil fuels. It's been capped but not vented as far as I know. How do you vent it (aside from the obvious answer of 'add a vent!')? Is this vented into the room or a vent outside?
THanks.

Both the room and the stack should have vents :RpS_thumbup:

 

[eoinm]

Both the room and the stack should have vents :RpS_thumbup:

Will be adding vents to the room alright - would you think adding vents to the UPVC windows would be enough or would I need an actual vent in the wall?

Regarding venting the stack, is this a vent into the chimney from within the room or added to the outside of the chimney?

 

[johniosaif]

Thanks for the reply and info. If I wanted to be 110% certain about stopping this reoccurring what combination of what you mention would you recommend? Is the plastic membrane option expensive or a specialist installation?

google the newton system, basically you fix the membrane to the wall at 600m centres,using special plugs supplied, also a rubberised jointing rubber for overlapping and joining sheets, simple enough once you have seen it done, depends on your skills etc, re keiths noticing the bridging( good spot) possibly water ingress from the roof either, check the exterior of the damp wall, is it brickwork, is it perished? have you got leaking gutters or downpipes, even the best need to be there to advise to the best of our abilities.. Photo the outside and have the roof looked at also... I know it goes on and on but best top be sure..

 

[bubbles65]

Will be adding vents to the room alright - would you think adding vents to the UPVC windows would be enough or would I need an actual vent in the wall?

Regarding venting the stack, is this a vent into the chimney from within the room or added to the outside of the chimney?

You want something like a mushroom cowl on top of the chimney mate and a letterbox vent in the old fireplace opening to ensure a flow of air through the old chimney flue :RpS_thumbup:

 

[eoinm]

You want something like a mushroom cowl on top of the chimney mate and a letterbox vent in the old fireplace opening to ensure a flow of air through the old chimney flue :RpS_thumbup:

Excellent, good to know.

 

[carlos]

As above all good advice..............:RpS_thumbup:

 

[eoinm]

google the newton system, basically you fix the membrane to the wall at 600m centres,using special plugs supplied, also a rubberised jointing rubber for overlapping and joining sheets, simple enough once you have seen it done, depends on your skills etc, re keiths noticing the bridging( good spot) possibly water ingress from the roof either, check the exterior of the damp wall, is it brickwork, is it perished? have you got leaking gutters or downpipes, even the best need to be there to advise to the best of our abilities.. Photo the outside and have the roof looked at also... I know it goes on and on but best top be sure..

Reading up on it now, the video they provide looks like it would be ideal. I don't think I'd do it myself and so the problem is finding someone in Ireland (which is where the house is) who can do this!

 

[johniosaif]

It should not be a problem finding someone in Ireland to do this considering the downturn, Which part of Ireland? there are some guys on here who are in Ireland and some who know people there...

 

[carlos]

Reading up on it now, the video they provide looks like it would be ideal. I don't think I'd do it myself and so the problem is finding someone in Ireland (which is where the house is) who can do this!

Try searching here

PCA - Property Care Association

 

[Arti]

Will be adding vents to the room alright - would you think adding vents to the UPVC windows would be enough or would I need an actual vent in the wall?

Regarding venting the stack, is this a vent into the chimney from within the room or added to the outside of the chimney?

most new windows if not all have trickle vents in them

 

[LongstrokePlastering]

How am i suppose to comment on this post with such good answears haha well done lads, the nail has defo been hit on the head, from all angles!

 

[eoinm]

It should not be a problem finding someone in Ireland to do this considering the downturn, Which part of Ireland? there are some guys on here who are in Ireland and some who know people there...

Its in the south east, Wexford to be precise. Will search here but if anyone knows someone in Ireland who can do that system or is familiar with dealing with this type of damp let them know I'm on the look out!

 

[eoinm]

Agreed, lots of good info provided quickly.

 

[eoinm]

Just by way of an update with this, we're having someone come out to survey the place this weekend. Regarding venting chimneys, from checking online I'm getting mixed messages.

There are two chimney stacks, one on each end of the house. All fireplaces are sealed over and there are no vents. However, the chimneys are all capped.

From reading it appears some people say if they're capped you don't need to vent them, others say they need venting no matter what.

Is there consensus on this matter at all?

 

[bubbles65]

If there is water in the flue it will come out through the walls and show as stains - or worse still - perished plaster, so to ensure that the water is dispersed via an airflow you should vent it. If you reckon there isn't much water in the flue then leave it capped. If the chimneys are on the gable ends you could put air bricks at the top and bottom to draw the moisture :RpS_thumbup:

 

[eoinm]

Quick update on this, looking for some opinions. Have had a few people look at the problem, one insisted it was rising damp, which it isn't. The others both agreed that while the wall is damp the methods to treat it were different. First person (damp solutions person) said the walls need to be tanked and then plastered over. This is a solution we've heard before and I'm not sure of how effective it will be.

The second solution is more interesting. The guy said the rooms / house is and always will be cold unless we properly insulate. This is true as before we decided to get this sorted the house was always chilly, even with the heat on. So he proposes to build a frame for these walls and put foil-backed insulation into it. Then attach the frame to the wall in a few places via small, treated timber blocks backed by a section of DPC sheeting. Before doing this the walls would be vented, maybe two or three vents put in.

So we'd end up with the wall insulated with a vented cavity behind it. My worry would be that the damp would come through the wood blocks despite them being treated timber and having plastic backing. Maybe a metal frame would be better? In any case, does this sound like a crazy solution or something that people have heard of before.

My main concern is that with either method we end up with those stains coming through again.

 

[carlos]

If the tanking is done right nothing will come through.

Or build an independent stud in front of it and vent some how.

 

[Danny]

Nicely Answered chaps