advice on finishing with clay or lime plaster

[josephcrawley]

I have a potential client who wants to finish the stove with a plaster. I haven't done this before. I have experience with both lime and earthen plasters so I have a good handle on that end of it. The thing I'm unsure about is dealing with thermal expansion. Do you guys use an air gap? using cardboard? or is it fine to plaster right on the brick? Also with lime my understanding is that drying the lime plaster out will end the curing process so what to do about that? Do people bother with a heat resistant fiber or go with the standard straw or hair?

thanks I appreciate this forum and all the helpful people on it

[danielray]

I haven't had an issue using non heat resistant fiber. It seems best to do multiple thin coats of sandy plaster to resist cracking followed up with an alis to prevent dusting. I haven't done any lime plaster around a stove.

[patamos]

For the first few feet around the fire box i always go double wall with air space via cardboard or ceramic fibre. The latter works better because little chunks of mortar that inevitably dislodge from the core have less chance of migrating somewhere that could create a point load.

Also, I embed fiberglass mesh tape (used in drywall seam applications) in areas of probably high stress. First a skim of plaster then bed the mesh tape with a trowel then more plaster. It is amazingly strong.

In general i've gotten away from lime finishes because they are less resilient than clay-sand finishes, and when they crack they are much harder to repair.