Plaster chimney externally

[K-S-L]

I have a masonry chimney on the roof that I plan to plaster while I have a skylift in place.

The mortar is quite bad in some places, do I need to repoint before I plaster, or is it enough to fill the mortar with compound while I smooth plaster?

Anything else one should know about plastering a chimney?

Grateful for answers, tips, and ideas!

 

[Åsa Lund]

Scrape out and re-grout first

 

[K-S-L]

Kratsa ur och foga om först

Thank you Åsa. Do you think you need to wait until the grout is completely dry before finishing?

 

[useless]

I should have waited a while so that the joints don't show through the plaster.

 

[Claes Sörmland]

Anything else one should know about plastering a chimney?

Today, chimneys made of brick are plastered with B-mortar and are usually "netted." A net is embedded into the plaster to make it more durable.

If you have an old house, the chimney is built with lime mortar. You might then consider plastering with hydraulic lime mortar. However, in the past, chimneys were often not plastered, as the lime plaster did not hold up well in exposed locations.

 

[K-S-L]

Today, chimneys made of brick are plastered with B-mortar and usually "netted". A net is plastered into the mortar to make it hold better.

If you have an old house, the chimney is built with lime mortar. You might then consider plastering with hydraulic lime mortar. However, in the past, non-brick chimneys were often plastered because the lime plaster didn't hold well in exposed positions.

Thanks for the response. I was planning to use KCB from Bösarp. Do you think it will work?

If I have to net the chimney, I need to remove the metal sheeting and I'm not really confident in doing that... so I was thinking of applying a thin plaster by hand.

It's an old house, and I would have liked to keep the brick if it were original, but unfortunately, it's not. The old chimney top was torn down sometime in the '60s and replaced with rather plain brick that doesn't fit with the rest of the house. So I'm considering plastering purely for aesthetic reasons.

Today, chimneys made of brick are plastered with B-mortar and usually "netted". A net is plastered into the mortar to make it hold better.

If you have an old house, the chimney is built with lime mortar. You might then consider plastering with hydraulic lime mortar. However, in the past, non-brick chimneys were often plastered because the lime plaster didn't hold well in exposed positions.