Hi, apologies if this has been asked before - I've had a quick check but I may have missed something!

Anyway, I need some advice on what I suspect to be rising damp on an internel chimney breast. I am getting fairly serious 'bubbles'/salts on the internal chimney breast walls in both my living room & in the kitchen on the other side. A previous damp survey said that damp-proofing the solid floor in the kitchen would fix that side & a missing brick (bridging damp) was the problem in the living room. Both have been rectified & replastered as part of a major renovation.

However, the damp is back & just as bad. The new plaster is showing salts etc again to a height of about 4ft on both sides but is only showing on the chimney brest & about a foot of internal wall either side. The problem is, the living room has a new fireplace/surround fitted & in the kitchen, there are cupboards/worktiops fitted & so to remove the plaster & have a damp proof course fitted would be a major upheaval.

Incidentally, when it hailstones, you can sometimes hear the stones hitting the back of the gas fire & I have also had a bird trapped behing the fire a few months ago & had to get someone to remove the fire to free it. One of the chimney pots looks to have some sort of cap on it (not sure what type) but the other doesn't - mabey this might be a cause??

There is, however, access to the inside of the chimney either by removing the gas fire in the lounge or by removing the cooker in the kitchen. If damp-proofing is what's needed, is there any way to have this treated without removing all of the plaster, removing half the fitted kitchen etc?

Any help or advice would be much appreciated!

seems to me that when it rains you have a paint pot full of water coming down your chimney, getting to the bottom and soaking into the brickwork where the heat of the room draws it through bringing with it salts found in the masonary...
i'd -
hack it all back off again to a foot above the highest point of damp...
run an 'upstand' injection right in the corner where the chimney breast meets the wall (may not be absolutely essential but would stop the damp in the chimney spreading into the walls)...
its a case of drilling every course of bricks and injecting dpc cream to a height of 4 feet, point up with sand/cement/sbr...
re-render with thistle dri-coat (12 quid a bag, b&q), finish with thistle board finish...

cap the chimney with an approved gas cowl, get a gasafe engineer to do this...

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http://www.peterborough-plasterer.co.uk/

A classic way to identify rising damp is that it only rises 4 foot above the surrounding ground.
The way it works is that water rises through the very small air bubbles entrained in the mortar when the mortar is mixed, but it is fighting gravity.
Chimneys are very hard to waterproof against rising damp as builders tend to throw all sorts of rubbish inside and this bridges the damp proof course.
However, it may be that you have a mixture of wet chimney caused by rain entering the top and exposed sides of the chimney and making its way down to damp proof level, where it is trapped, like water in a sponge, and because the chimney is wet, it is also cold, and this attracts water vapour from the air, that condenses into the chimney.

Start with the easy option, fit a cowl to the top of the chimney to stop the rain entering and paint the exposed parts of the chimney with a silicone based masonry paint, that will stop the rain entering the bricks and mortar.

Keep the temperature of the rooms on both sides steady 24/7. Water vapour is always attracted to a cold surface, you see this on your windows during the winter as condensation, you don't see the same condensation on the walls because the water vapour sinks in moving towards the cold centre of the chimney.

Keep the rain out and over the warm days of summer with the rooms on both sides also keeping warm, the chimney should at least dry a little, if it is rising damp, then after each lot of rain, the problem will return. If it is rising damp the only solution is to open the chimney and remove the rubble inside and or install a chemical damp proof course. This will not be easy as it requires careful work.