Have you got a damp stain on your chimney that you can’t seem to get rid of?
Is it hygroscopic salts?
Is it a leak?
We have seen many cases where roofs have been repaired around chimneys a number of times and the other roofer-builder has said the other Company didn’t do the lead work correctly, roof repairs, chimney repairs, or the pointing etc etc and then they still have a damp stain on the internal chimney breast.
Recently I went to carry out a damp survey in Wiltshire, they had literally given up, and this is how the story goes……. My client purchased a property 6 years ago, it was noted by the surveyor before purchase that the internal chimney breast had staining and the chimney probably needed small pointing works, and further investigation was necessary. This work was carried out after they purchased the property in the summer and was decorated, a few months later on in the year the damp stains on the chimney breast came back, this time it was worse than before. So they called the roofer back in, he checked the chimney and tested it with a hose pipe and couldn’t see any problems, and he disappeared very quickly…….. They then called another roofer-builder, this guy pulls around on the lead flashing and seems to think the chase isn’t deep enough and also it needs a new roof, tells the client this is what needs doing, orders the scaffold and off we go again! The damp patch on the chimney seems to slowly shrink and disappear over the next few months, then its back again……… by this time my client said they couldn’t believe it. They then called the roofer out again and explained that the damp stain is back! He couldn’t find the cause and he disappeared very quickly like the last guy.
Next comes the roofer with the all singing and dancing website, more professional, and more knowledgable, and he seems to think the chimney needs to be simply taken down and capped over with some ventilation. Seems like a good sensible idea they think……….A couple of weeks later the scaffold lorry turns up, up goes the scaffolding, up goes the roofers, down comes the chimney, this is then all capped off, vented and pointed and looks like a brilliant job. The damp patch doesn’t go and the roofer can’t seem to find the cause….same old story!
You can imagine what my client was thinking now. By this time they had given up and thought they would have to put up with it. They then get some rising damp problems and contact a couple of damp proofers to come and carry out a survey, I then come along and have a chat about the high ground level causing the damp problem at the front, whilst looking at the front I said, “I see you’ve had a new roof then”, and bang….I get hit with it. And I said “thats probably salt damp” “Whats that” my client said, I then showed them a couple of case studies I had on damp chimneys. That was the Eureka moment for them. I went one better than that though, I showed them the damp patch grow, and to do this I use a humidifier, this can produce high relative humidity very quickly, give it 5-10 minutes you can see the damp patches grow. The below pictures show the humidifier in action raising the relative humidity of the room to show the hygroscopic salt damp patch growing.
This is before I raised the relative humidity.
This is after , you can see the hygroscopic salts on the chimney breast now (damp looking patch at the top of the chimney breast), also notice the vertical profile up the wall, following BRE Digest 245.
This thermal image shows a quite a large level compared to the bottom thermal image
The below thermal image shows a difference in temperature between Sp1 and Sp2 being .3 degrees, this shows how powerful thermal imaging can be using temperature differences. My client now was convinced that the problem could be solved after spending literally thousands of pounds for nothing. All results were carried out to BRE Digest 245 methodology giving us quantitative results and the client complete peace of mind.
BRE Digest 245 methodology results
Picture 1 shows after the sample has been filtered with a filter paper and de-ionised water.
Picture 2 shows that Nitrates and Chlorides are present
Salts analysis matched with the drilled profile and visible salt damp staining, this confirmed hygroscopic salts from long term burning of fossil fuels, and no free moisture which means that there is no leak in the roof or around the chimney and probably never was.
Can a damp meter be used to tell you exactly what is going on?
Using a damp meter to test for hygroscopic salts and free moisture especially around a chimney will not tell you what the problem is, the damp meter can’t differentiate between free moisture and salts.
I often get asked the percent of chimney damp problems issues that is solely related to hygroscopic salts only. In about 75% of my surveys free moisture is present from penetrating damp, and or rising damp at the base of the wall.
Please click on the below two links that also show other chimney damp causes.
The below link is of an interesting survey again relating to a damp chimney issue.
The below link shows another interesting survey, again eating to chimney damp issues. This survey show another issue where we used data loggers to help diagnose the issues.
Below is a time lapse video of salt damp
Below is the before and after pictures of the time lapse showing the salt damp on where a chimney used to be in a property in Trowbridge Wiltshire.
Note the dampness on the wall in the below picture, this is hygroscopic salts absorbing moisture from the air that has been made humid by the humidifier
Contact Complete Preservation of Trowbridge Wiltshire for advice, or to book in a survey, we offer site surveys up to a 3 hour drive.
I’m often asked is it likely to be hygroscopic salt damp or just free moisture…..it is impossible to tell using a damp meter and even I find that sometimes I get it wrong without the gravimetric sampling data.
We also offer a service where you can post your plaster sample to us for us to test using the laboratory methodology in BRE Digest 245, we can then tell you if the sample has any free moisture, and or hygroscopic salts present. If you wish to have this carried out please contact the office and I can advise you on the necessary steps.
Each sample costs £60.00 including vat.
We also offer chimney aerial surveys , to look for defects like lead flashing detailing, pointing defects etc. These aerial pictures along with the data collected, help us to ensure we offer correct diagnosis. Complete Preservation can carry out the survey and all the necessary remedial works for chimney defects and all internal works to the walls where needed.
Our main website is www.completepreservation.co.uk
We can be contacted to arrange a survey on 01225 769215