Getting rid of damp from an old building

[amateur]

Our son-in-law inherited an old cottage in the Peak District from his aunt.

 

It's about 300 years old (the cottage, not the aunt), and now, having re-plastered and re-decorated it, he is finding damp and mould on many of the walls.

 

The walls are local stone, single skin and no damp course (obviously).

 

Does anyone have any thoughts on how to dry out and permanently rid the building of damp?

[guest1957]

Dehumidifiers in as quickly as possible and then get a local specialist to advise?

[dog tired]

Get it injected mate.

[artschool]

its complicated and if he has already replastered then he has limited options.

 

if it was a refurb you could look at:

injected dpc (as mentioned)

lining to the walls.

introduction of a dpm.

additional ventilation to the walls.

tanking

better drainage outside the property(aco drains, french drains etc).

[-Mongrel-]

Is it heated?

[al4x]

Mould suggests it might be lack of ventilation, be a little careful with injected dpc's as old buildings were meant to breathe hence the lime mortar etc. I'd check all guttering, outside ground levels and where it's occurring before looking at doing much

[kingnewport]

open a window

[whitehackle]

Where in the peak district? Not to far from me. I would be tempted to tank the damp walls but will mean re plastering, after of course you have made sure there are no leaks and outside drainge.

There are lots of things that could cause this

[lineshooter]

Have a look at this http://www.passivent...re_removal.html in conjunction with the above comments.

 

We are using this a lot in older single brick properties, etc it`s very good system, no more black mould.

Edited January 9, 2013 by lineshooter

[Fisheruk]

What plaster did he use? Is the building ventilated to enable it to breath? Post some pics. We may be able to help. Have a look at this website. http://www.restoration-design-partnership.com

Edited January 9, 2013 by Fisheruk

[HDAV]

It will have a damp course just not a modern one and the modern plaster may be the issue.......... has he replaced the windows? Or done any other works?

[Malik]

I find this alot at this time of the year with our tennants. Most of the cures have been mentioned above.

 

Ventilation - you could install wall vents in the most effected area/s (if possible) or open a window or door.

Dehumidifiers - to draw the moisture out. Just remember, if there is alot of moisture the tank will fill up quite quickly and you will need to keep emptying it. plus keep all your windows and doors shut for this. you want as much moisture out of the walls as possible.

Heating prevents it.

Depending on what surface the mould is on, a thin bleach solution maybe required to wash off the mould. just be careful with the warm water bleach ratio and dont scrub too hard!!!!

 

Other factors such as damaged guttering or drainage can cause bad cases.

[Paul T]

The problem could a number of things e.g. external ground level too high, faulty guttering/RWPs, but it is more likely that the stone and mortar is porous. Couple that with poor ventilation and no insulation and you will have a damp problem.

 

The best remedy ain't cheap, but it will solve the problem permanently:

• Firstly I'd get rid of all the old plaster on the external walls - If it's been on any length of time it's probably horsehair and it does tend to hold moisture. Check the external pointing is in good repair and get a dehumidifier going and try to dry out the walls a bit.
  
• Check the windows have trickle vents fitted and if not, fit some - poor ventilation is a major cause of condensation (damp) particularly high up on cold walls
  
• Then apply a Sika 1 waterproofing system (Google it) to the walls. This will stop the moisture getting through again - it's brilliant stuff.
  
• You could also add some insulated plasterboard at this point too, which would be a great benefit - and if you stuff some plastic conduit in the insulation to create some ceiling to skirting drops, it makes re-wiring a doddle too!
  

If he's inherited it (so doesn't have a mortgage) best invest some cash now in a long term solution

[Fisheruk]

The problem could a number of things e.g. external ground level too high, faulty guttering/RWPs, but it is more likely that the stone and mortar is porous. Couple that with poor ventilation and no insulation and you will have a damp problem.

 

The best remedy ain't cheap, but it will solve the problem permanently:

• Firstly I'd get rid of all the old plaster on the external walls - If it's been on any length of time it's probably horsehair and it does tend to hold moisture. Check the external pointing is in good repair and get a dehumidifier going and try to dry out the walls a bit.
  
• Check the windows have trickle vents fitted and if not, fit some - poor ventilation is a major cause of condensation (damp) particularly high up on cold walls
  
• Then apply a Sika 1 waterproofing system (Google it) to the walls. This will stop the moisture getting through again - it's brilliant stuff.
  
• You could also add some insulated plasterboard at this point too, which would be a great benefit - and if you stuff some plastic conduit in the insulation to create some ceiling to skirting drops, it makes re-wiring a doddle too!
  

If he's inherited it (so doesn't have a mortgage) best invest some cash now in a long term solution

Well need to be careful giving specific advice without knowing details. I am very sceptical about this advice, it could cause further major problems.

As soon as you remove plaster from old walls in domestic properties you are required to upgrade the thermal integrity of the walls as required by Part L of Building Regulations 2010, even if it is an old building.

[Fisheruk]

It will have a damp course just not a modern one and the modern plaster may be the issue.......... has he replaced the windows? Or done any other works?

At 300 years old and rubble stone construction almost certainly will not have a DPC.

[Fisheruk]

Mould suggests it might be lack of ventilation, be a little careful with injected dpc's as old buildings were meant to breathe hence the lime mortar etc. I'd check all guttering, outside ground levels and where it's occurring before looking at doing much

This is good advice.

[artschool]

 

Well need to be careful giving specific advice without knowing details. I am very sceptical about this advice, it could cause further major problems.

As soon as you remove plaster from old walls in domestic properties you are required to upgrade the thermal integrity of the walls as required by Part L of Building Regulations 2010, even if it is an old building.

apart from the cost I can't see how complying with or exceeding the building regs is a bad thing?

 

agree with you with regards that it's impossible to give the correct advice until you have seen a building.

[Fisheruk]

 

apart from the cost I can't see how complying with or exceeding the building regs is a bad thing?

 

agree with you with regards that it's impossible to give the correct advice until you have seen a building.

I agree with you, I'm not saying it's bad to comply with the regs, it is essential otherwise there may be major problems if you come to sell in the future. Good. To see so many willing to give advice but we need to be careful,without seeing the problems.

[Paul223]

has the outside been repointed, if so was a lime mortar used, if a cement mortar has been used this will be a big contributing factor, do not take up the idea of sealing the outside, the walls need to breathe

[amateur]

Many thanks for the above advice, and for the pm's.

 

I'll pass all of this on to my son-in-law.

[timps]

First of all you do have to ascertain where the dampness is coming from, if you get a specialist in and they come with a hand held moisture meter and use that alone, send them packing.

 

The correct ways to test are described in BRE Digest 245 and outlined in BS 6576:2005+A1 2012

 

Most probable are:-

A) Condensation :- if condensation is a problem then the substrate behind the plaster will be relatively dry. :- Increase ventilation

 

B ) Rain penetration due to defects in construction materials, leaking gutters or roofs and or doors and windows:- Penetrating damp is likely to cause isolated patches of damp that increase and decrease in size and unlikely to be the full length of the wall and usually above ground level. :- Fix by repointing or fixing the gutter etc. or if prolific tanking or drylining.

 

C) Drains.

 

D) Contamination of surfaces by hydroscopic salts. :- These salts can be present in old buildings and absorb moisture from the atmosphere even with good ventilation. The substrate behind the plaster will be relatively dry and the only way to test for them is in a lab:- Remove the contaminated plaster.

 

E) Rising damp. Visible signs are a tide mark where the water stops rising. This can only be assessed correctly by doing a moisture gradient on the substrate (wall not the plaster and not with an electronic damp meter) which requires you drilling holes in the wall at different heights:- If rising damp then chemical DPC or Disc cutting and inserting a new one.

 

A word of caution I doubt rising damp would be the problem, (damp proof courses have been mandatory in all British buildings since the Public Health Act of 1875) but this is the first thing they try to sell you. If it is not rising damp the chemical injected DPC does nothing to help, however the replacement of the plaster during the injection process with a cement based water resistant plaster then cures/masks the problem so it is wrongly assumed the chemical DPC did its job.

 

Edit to add: Forgot to add a very common one on old buildings, plaster touches the floor or is at ground level, water is then sucked up through the plaster. The substrate behind is dry:- remove bottom of plaster so hight is above ground or get rid of flowerbeds that have raised the outside ground level.

Edited January 10, 2013 by timps

[HDAV]

 

At 300 years old and rubble stone construction almost certainly will not have a DPC.

It will, it may have failed but it will have a damp course they have been used for centuries, a layer of slate in the walls is a common one, or tar, none pour ours stone etc. researched the topic heavily and some great stuff written by an expert in historic buildings....... "Modernisation" often causes these sorts of issues

[Fisheruk]

 

It will, it may have failed but it will have a damp course they have been used for centuries, a layer of slate in the walls is a common one, or tar, none pour ours stone etc. researched the topic heavily and some great stuff written by an expert in historic buildings....... "Modernisation" often causes these sorts of issues

There's a lot of twaddle written on the Internet and even more by some so called academics. I'm not a betting person but I would be very surprised if a 300 year old cottage has an original DPC. I've only been working as a Building Surveyor for 49 years and having surveyed thousands of properties regarding dampness, I'm still learning!

[rimfire4969]

We have done loads to sort the damp in my old place dating about 1740. Including injecting, new lime pointing and render, decreasing outside ground level, tanking and we have several dehumidifiers running, we still have damp issues but a heck of a lot better than it was, now limited to a couple of places. We have come to terms with the fact that if you have a very old place there are going to be damp issues especially where I live.

[Gimlet]

Be very wary of using injection damp proofing or tanking if the house is terraced or semi-detached. Neither process stops damp ingress, they mask it or move the symptoms somewhere else. You have a legal duty of care to your neighbours and you must notify them of any damp-proofing work you intend to carry out on a party wall. If you undertake the work without their knowledge and they suffer damp problems or increased problems themselves as a result, they can sue you.

 

All basic maintenance requirements of an old solid wall building should be addressed first as a matter of course before anything else is done. Which is minimising damp ingress by maintaining drainage, guttering, pointing, vegetation, french drains, outside ground levels and surface run-off; and ventilation: windows, chimney flues (should be open with vent cowls fitted), and roof sarking. If the roof has been recovered with non-breathable felt tile vents need to be fitted.

All these things should be in text book condition before you start injecting chemicals or sealing masonry. If the building is listed either treatments can be classed as structural and require permission.

Do the basics first.

Edited January 10, 2013 by Gimlet