I have significant damp penetration in a chimney.
The chimney was built in 1880 of stone blocks with limestone corners. The packing between the stones is earth and ash. The mortar used was, I believe, a lime ash mix.
The chimney was rendered with a Portland cement mix in the 80s.
About 5 years ago there was damp penetration into the ceiling and chimney breast in the room below. The rendering continually cracked, even after being repaired, so was removed. There had been considerable water penetration that had damaged the limestone corners. These were replaced with engineering bricks and a Portland cement/sand mix to keep them in place. The rest of the chimney was re-pointed using natural hydraulic lime (3.5) and sand mix using the manufacturers recommended mix of 3:1 sand/lime. (I was aware of the need for the chimney to 'breathe'.)
Unfortunately there continues to be significant damp penetration. I believe it is worse than before. It is not the flashing as this has recently been replaced. The flaunching and chimney pots are sound too. The re-pointing looks damp. Is it letting in water? I would be very grateful for any advice, as I really don't know what the problem is!
Are you a tradesperson and able to answer this question?
This is a common problem with late 1800's builds. these properties were built to "breath" and are reliant on an even percentage of water ingress and exhaust which is why a chimney is so important to be used in this type of property. Using cement based products is your cause of your problem. The alternative method to keeping the property breathing properly is to ONLY use breathable material IE lime plaster/bonding and breathable paints. keeping your chimney open is also a great benefit as your heating will allow moisture to exhaust through it.
With regard to the continual water ingress i assume this is through your chimney.
In many cases, rain penetration is caused by poorly designed or maintained building details (e.g. blocked down pipes or leaking gutters and age related masonry damage) causing large amounts of rainwater to flow over a small section of masonry. In these cases, the penetrating damp can usually be cured by rectifying the defect.
In other cases rain penetration can be caused by the masonry wall not being weather tight enough to withstand local weather conditions. Often the weather tightness of the masonry can be improved using external render, cladding, or weatherproof paints. However these solutions all change the visual appearance of the masonry. The alternative is to use a weather proof clear paint and can be applied to all masonry to try and cure too much water ingress. This is a suitable solution to use without having to change the appearance of your property.
There is allot involved in regard to this but please feel free to contact us if you would like us to send you are full guidance pack for free in regard to this. As this is something we advise on regularly.
Kind Regards
Peter
Phoenix UK Renovations Ltd
