Removing plaster from brick

[JKW05]

A 100-year old building is being demolished adjacent to another 100-year old building that is to remain. The walls are all brick masonry. The wall that will be exposed to the exterior has plaster applied directly to the brick. The owner would like to expose the brick and paint it. Any thoughts on the best way to remove the plaster?

 

[hokie66]

My only thought is that if he removes the plaster, the wall will leak.

 

[civilperson]

Sand blast and polyurethane coat the brick.

 

[hokie66]

Sandblasting will erode the mortar, distribute lime over the surface of the brick, and the brick will look white under the polyurethane. Speaking from experience of one who has done it and created a mess. Just make sure if you do this, you test an area first before applying all the polyurethane. Probably will require a lot of hand work, wire brushing, washing, etc. to achieve a satisfactory finish.

On an exterior wall, the clear varnish will not last long. Polyurethane works works well away from UV light, but not in sunlight.

 

[dik]

Do not sandblast the brick! This can remove the 'fireskin' and leave the existing surface with little protection against deterioration.

Dik

 

[JKW05]

The plaster-on-brick is a little awkard here because it was only applied directly to the brick at the upper floor. The lower floor has furring strips. I am concerned about damaging the brick by removing the plaster, but there are two problems with leaving the plaster on:

1) The plaster starts about 8' down from the parapet coping. So it would seem that water would get behind the plaster and over time start spalling the plaster off in pieces.

2) This wall will be very prominently visible to the main street of the small town it is located in. Aesthetically, the owner (and the town) wants the exposed brick.

hokie66:

The wall is a 12"-thick, 3-wythe wall. We have documentation that it was originally the exterior wall of that building when it was built in ~1890. The other three walls of the building are of identical 3-wythe brick that has been painted. The existing "barrier" walls appear to be performing just fine. I definitely would not permit sand-blasting. Repointing and repairing/replacing damaged brick is anticipated.

Didn't know if this additional information would lead to any other comments. Thanks for the replies.

JKW

 

[concretemasonry]

When you repair the mortar joints, make sure you use a proper mortar and not some high strength Type M or S. Have a local masonry specialist look at the construction for some morat suggestions. Mortar strength is not a priotity, but compatability is.

 

[hokie66]

I think you have to remove the plaster by hand tools, chisel and hammer. Then you can paint the walls with 100% acrylic paint. Maybe some kind of sealer before the paint, but I definitely would not use a clear finish, as it just won't last.

 

[dik]

I've tried to upload a file on Historic Masonry for added information.

Dik

 

[JKW05]

hokie66: That was pretty much the direction I was taking, but some of the demo contractors were raising questions about it. I think they were trying to find an easy-out.

dik: thanks for the article.

Thank you all for your replies.

JKW