# Repointing a Chimney-Can You Use Plastic-Based Mortar?

**URL:** <https://boards.straightdope.com/t/repointing-a-chimney-can-you-use-plastic-based-mortar/733526>\
**Category:** Factual Questions\
**Created:** [October 4, 2015, 7:03pm UTC](https://boards.straightdope.com/t/repointing-a-chimney-can-you-use-plastic-based-mortar/733526 "2015-10-04T19:03:05Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\
**Post date:** [October 4, 2015, 7:03pm UTC](https://boards.straightdope.com/t/repointing-a-chimney-can-you-use-plastic-based-mortar/733526/1 "2015-10-04T19:03:05Z")

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My house in 93 years old, and the chimney needs repointing. Chiseling out the old mortar is easy-but filling in the areas removed is a big job. My question:  
-can you use that plastic mortar patch that comes in tubes? It is expensive, but easy to apply (you inject it from a caulking gun).  
-if using regular mortar, can you squeeze it in from a pastry frosting bag?  
Applying with a trowel seems like a hard way to do this. at any rate, access to my roof is easy, and it should be a two day job.

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**Author:** ![herman\_and\_bill](https://avatars.discourse-cdn.com/v4/letter/h/f1d935/32.png) [@herman\_and\_bill](https://boards.straightdope.com/u/herman_and_bill)\
**Post date:** [October 4, 2015, 7:31pm UTC](https://boards.straightdope.com/t/repointing-a-chimney-can-you-use-plastic-based-mortar/733526/2 "2015-10-04T19:31:27Z")

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You may get away with it if your chimney has a liner, but being 93 years old I kind of doubt that you have one. What you want is called a grout bag, your masonry supplier should fix you up.