Condensation in closed chimney

[vbhardwaj87]

Hi All!

We have recently purchased a 1930s built house that was lying unoccupied for over a year. Ever since the purchase we have been discovering one problem after another. There is damp everywhere, wetness and clay heaving in the crawl space, roofing needs rebuilt, etc. We spent all our money on the purchase and now have no additional budget to spare for the multitude of repair work needed. We are relying solely on our own manpower, DIY expertise and the guidance from you all.

Coming to you all today for a chimney related concern. There are 2 chimneys on the roof and 1 of them has been closed. However, there’s condensation happening in that closed chimney. In fact, the room right below this chimney has a major damp issue. Damp spot starts from near the top and spreads in L shape to the bottom and to the right of the wall.

We have been told installing airbricks in the chimney should help. Reaching out to get some guidance. Given the chimney is closed we are not sure what’s the source of condensation - as in from where is this hot / cold air coming in. Also, will air bricks solve the concern?

Thank you all very much in advance for all the guidance and help here.

 

[JohnD]

Chimneys need to be ventilated top and bottom or they will suffer internal condensation.

An airbrick in the bricked-up fireplace and an opening at the top, are usually sufficient.

I don't know how yours has been "closed"

 

[^woody^]

Once flue gas acid has leached into the wall, in addition to venting the flue, you need to hack off the plaster and seal the face of the wall before replastering.

 

[tell80]

OP,
Perhaps you will post pics of the roof chimney stack, & a pic of the upstairs chimney breast?
Each fireplace has its own flue, & your flues will almost certainly need sweeping & smoke testing - the blocked fire place will need opening up for access.
Both your flues will need through ventilation from bottom to top - stay away from stack air bricks, there are ventilation cowls available for inserting into the chimney pots.

All damaged plaster plus 300mm beyond the last signs of damage will need hacking back to brick.
Renew with 4:1 render mix of sand & NH lime.

Closely examine your floors, skirtings & ceilings for damage.
If you go into the loft & examine the loft chimney breast, & find signs of water leaking down the c/b then close-up pics of the stack flashings & flaunching would help?
,