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Damp Proofing

Tanking found on internal chimney breast

Hi. We are wanting to have the chimney breast in our dining room opened up and taken back to bare brick. We have taken a small part of the plasterboard away to see if there was a hole already there and have found that the chimney breast has been tanked. Is this going to be a pr6or could we just remove this and open it up anyway? Thank you

4 Answers from MyBuilder Damp Proofing Specialists

Best Answer

The chimney breast was tanked because the brick work is contaminated with ammonia sulphate salts, this causes a condition called hygroscopic dampness. It’s always best to ventilate a chimney flue top and bottom to slightly relieve the moisture content of the bricks. If you want to expose the bricks for aesthetic reasons it’s ok but don’t seal the exposed bricks as they need to evaporate minute moisture particles.


Answered 20th Mar 2020

Hi I think there is some confusion here the poster suggested that they wanted to "open up" the chimney brest and have exposed brick feature I think what they accually mean is open up the fire well (the fire back) below the supporting lintol to make this a centerpiece feature of the the room! If this is the case the that's no problem the exposed brick work should be thoroughly cleaned and treated with salt inhibitor solution to combat hygroscopic salt contamination.


Answered 20th Mar 2020

I would recomend that you don't touch the tanking. To get the look you are after just over clad the plasterboard with brick slips. These are real bricks cut into thin slices and come in various shades and colours.


Answered 22nd Mar 2020

If this builder has seen the chimney then he or she may have a good idea of the problem.
I would say with out seeing the chimney that if there were no ventilation in the chimney then that's why it was wet in the first place, a sealed chimney will sweat with out ventilation in the breast and also vented at the top.
The chimney may have been tanked by some one who didn't know what they were doing, or if there was penetrating damp.


Answered 24th Mar 2020

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