chimney mortar, antique brick

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Old 05-29-11, 04:47 PM
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chimney mortar, antique brick

I have an old 3 family in Worcester, MA, built in 1890. The mortar in the chimney is coming out. I have not tested the mortar, and have not repointed a chimney in many years.

I read that Type N mortar is okay, THEN read a bunch of stuff online that the only safe mortar to use on antique brick & mortar is lime/sand mortar, because it's soft and will not spall the brick like rigid, modern cement based mortars do.

Any suggestions for this? Can I use Type N with extra sand, or mix something else in to make a softer mortar?? Any suggestions for sand type? A masonry site suggested rounded river sand over... whatever the alternative is.

Several sites said only lime mortar will work for old brick and mortar, but that is not something the local home Lowes Depot has. Suggestions as to what/where to buy the right mortar?
I'll post some pics ASAP of the chimney. ANy help is most welcome...

thanks
 
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Old 05-29-11, 06:39 PM
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Nothing added to applied over Type N or mixed will work as well at a sand/lime mortar for old brick.

The ASTM mortar specifications suggests using the weakest mortar possible and still catty the load.

HD and the others are just cheap commodity stores that have little idea about things made before 1960 or so.

Dick
 
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Old 05-30-11, 10:45 AM
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Dick, thanks for the reply. I was in Lowes the other day in the masonry section and asked for help. One of the employees suggested a hard cement based mortar, which would probably destroy the bricks or come out within 2 years.

I was also surprised how expensive their masonry tools were, a lot more than HD...

I don't know much about mortar, but I know antique bricks need special care
 
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Old 05-30-11, 12:09 PM
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one other comment - I was on a site geared towards historical renovation and restoration - they said lime mortar is about 200 psi hardness, a lot less than Type N - there is a Type of mortar which is only 75 psi hardness

a good link: https://environment7.uwe.ac.uk/resou...r/section4.htm they say:
“Mortar should never be stronger than the bricks” is a well-known maxim in the bricklaying world." from another site: In general, houses built before 1930 have softer brick, which makes them likely candidates for old-style lime mortars.

BTW, I found a local masonry supplier that has hydrated lime, and sand of course, they are the only ingredients I need to point the antique brick chimney! yeah!!
 
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Old 05-30-11, 02:11 PM
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It just makes sense to use what was used in 1890 since it did well for a long time. - Just open the joints a bit and clean them up before pointing.

Dick
 
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