I have a 1920's town home with exterior brick walls. In the upstairs bedroom on the northwest corner, I occasionally see condensation forming and running down the brick wall in the winter. This is probably caused by the warm moist interior air condensing on the relatively cold exposed brick wall.

I applied a few layers of dry-lok to keep the soft mortar from shedding, but this also seems to have stopped some of the condensation.

Is there a product that is similar to the matte clear dry-lok that might be better able to reduce condensation on the brick wall? If not, what other steps might I take in order to reduce the formation of condensation on the brick wall short of furring it out and insulating it?

brick wall

  • Add a fan to the room. This will increase evaporation considerably, preventing "running down" condensation.
    – dandavis
    Aug 23, 2019 at 17:04
  • do you mean an exhaust fan or a ceiling fan. I have installed a ceiling fan, and I suppose running it anticlockwise might mix the warmer and cooler air in the room. That might help with condensation.
    – Britt
    Aug 24, 2019 at 3:05
  • a ceiling fan or even a box fan or pedestal fan that hits the wall. i had the problem in a dorm room way back when with cinder block walls, and the fan made a huge difference.
    – dandavis
    Aug 25, 2019 at 1:37

1 Answer 1


The only thing that will prevent condensation on the wall is insulating the wall (and you will need a vapour barrier inside the insulation). Sorry.

(Technically, you can prevent condensation by reducing the moisture content of the room. Note, by this I don't mean "relative humidity", I mean "amount of water vapour measured in e.g. g/m³". This will either mean making the room unpleasantly arid, or unpleasantly cold, or both.)

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