I have uncovered the chimney in the kitchen, behind a row of cabinets with nailed-on masonite. Since the plaster looked like it had been hit by a hailstorm, I quickly knocked it off. Hollow plaster and pure sandcastle in equal parts... The long-unused connections for the wood stove, damper, and kitchen fan had really mediocre patches, so they crumbled away along with the plaster.
The chimney is definitely built with lime mortar (circa 1926) so I plan to use lime mortar for the work, but there are several options available nonetheless... The weakest seems to be Sepro142, and it's probably sufficient for plastering. But can I use that mortar to seal the openings? There's lime-cement mortar, hydraulic lime mortar, etc.
Furthermore, I’ve looked into a gypsum plaster (Gypro) for plastering, it seems convenient.
I use the chimney for a stove, so the choice of materials must be correct.
Grateful for advice.
The chimney is definitely built with lime mortar (circa 1926) so I plan to use lime mortar for the work, but there are several options available nonetheless... The weakest seems to be Sepro142, and it's probably sufficient for plastering. But can I use that mortar to seal the openings? There's lime-cement mortar, hydraulic lime mortar, etc.
Furthermore, I’ve looked into a gypsum plaster (Gypro) for plastering, it seems convenient.
I use the chimney for a stove, so the choice of materials must be correct.
Grateful for advice.
you can plaster with ordinary plaster C, you can do masonry with mortar B, we always do that and it works great.
I would recommend you to remove all the plaster all the way. From bottom to top. Carve out old mortar about 3 cm in the joints between all the bricks. Mix new mortar and press it into the joints. You can stop there if you think exposed bricks look nice. In that case, wash the bricks clean... it will look great...
Otherwise, you can continue and plaster the chimney as usual... finally, you can then lime paint the chimney in the color you desire... white lime is the most common.....
Otherwise, you can continue and plaster the chimney as usual... finally, you can then lime paint the chimney in the color you desire... white lime is the most common.....
Considering that you will be burning - meaning there will be temperature differences and thus material movements - the mortars should be as similar to each other as possible. When talking to Maxit, it works to use 142 for masonry, but they recommend using the hydraulic 148. You can then do the surface plaster with 142/144. Personally, I would prefer lime plaster over gypsum, as it provides a nicer finish with a more classic plaster feel. Keep in mind that bricks absorb a lot of water, so water generously before applying the plaster to avoid cracks.
Thanks for all the answers 
There is a lot of expertise here.
Swehjo; as you reason, I've also been led to believe that one should use mortar as hard as the existing joints, and not plaster with harder mortar than the joints to avoid cracks later. The fireplace is "on the other side," and is connected to a flue that does not face the side I'm working on, but I have no knowledge of the flue integrity, so it's best to do it right.
The reason I'm looking into gypsum plaster is that it seems easier to work with and can be applied in thicker layers. Good for me, since there are some irregularities to fill in.
Additionally, I am a novice at this, and I assume gypsum plaster is more "creamy," similar to house fix.
There is a lot of expertise here.
Swehjo; as you reason, I've also been led to believe that one should use mortar as hard as the existing joints, and not plaster with harder mortar than the joints to avoid cracks later. The fireplace is "on the other side," and is connected to a flue that does not face the side I'm working on, but I have no knowledge of the flue integrity, so it's best to do it right.
The reason I'm looking into gypsum plaster is that it seems easier to work with and can be applied in thicker layers. Good for me, since there are some irregularities to fill in.
Additionally, I am a novice at this, and I assume gypsum plaster is more "creamy," similar to house fix.
I have filled 10 cm deep holes with lime plaster but in 2-3 rounds so that it would harden somewhat in between. Otherwise, lime plaster is like any coarse putty. It can hang like a tongue from the tool without crumbling into small clumpsLurvnos said:
. I don't know how to describe lime plaster but it is surprisingly pliable to work with. I put it on with a tool called "skånska" just like applying putty without throwing it on the wall like the pros do - less waste on the floor . I never thought that lime+sand could become such a good material to work with. Then you have plenty of time to smooth and even out the surface with a wet sponge board... until you are satisfied. I agree with Swehjo that gypsum plaster will become more perfectly smooth, with less visible craftsmanship. gaia gaiaThank you Swehjo and Gaia, you gave me the courage to try
This is actually going really well! I wonder if I'll get any surface finish on it... :
I'm still just working on the underlying layers, sealing up the openings, and so on.
I sprayed the fixed parts with water from a "pump-up" type spray bottle, and I completely dunked the loose stones in a bucket for a while.
The instructions on the bag say to keep it moist for three days... should I set up the sprinkler in the kitchen? Or is it enough to spray it a couple of times a day?
It's really fun to throw on the plaster! Splat! Splat! Half of it ends up on the floor...
This is actually going really well! I wonder if I'll get any surface finish on it... :
I'm still just working on the underlying layers, sealing up the openings, and so on.
I sprayed the fixed parts with water from a "pump-up" type spray bottle, and I completely dunked the loose stones in a bucket for a while.
The instructions on the bag say to keep it moist for three days... should I set up the sprinkler in the kitchen?
Or is it enough to spray it a couple of times a day?It's really fun to throw on the plaster! Splat! Splat! Half of it ends up on the floor...
Half on the floor is how it looks when the pros work too ... A layer of paper or plastic underneath so you can "reuse" it. Spray 2-3 times a day with your sprayer, preferably have plastic on top to delay evaporation. Perhaps we should have mentioned earlier :, but the lime plaster needs to cure for quite a while before it can be painted unless you're using pure lime paint. The plaster needs to dry out and "silicize" completely before any paint can be applied. I recall we're talking about 1-2 months for, for example, silicate paint. It might be completely crazy but I would wait as long as possible. It takes a looong time before the lime reaches its full strength.
... A layer of paper or plastic underneath so you can "reuse" it. Spray 2-3 times a day with your sprayer, preferably have plastic on top to delay evaporation. Perhaps we should have mentioned earlier :, but the lime plaster needs to cure for quite a while before it can be painted unless you're using pure lime paint. The plaster needs to dry out and "silicize" completely before any paint can be applied. I recall we're talking about 1-2 months for, for example, silicate paint. It might be completely crazy but I would wait as long as possible. It takes a looong time before the lime reaches its full strength.
I repaired the plaster on our chimney with Maxit Serpo 142, it worked great. I've never done anything like this before, nor have I used lime mortar. But it went perfectly well.
I checked in the morning and evening in the following days and sprayed on more water, it went well except for a tiny crack where I applied at least 50mm in different layers. There I took a regular brush, dipped it in water, and painted on. Then the cracks filled in.
I am satisfied anyway, and it hasn't cracked yet, even though we've fired up the stove so much it almost changed shape, right after the chimney sweep approved the installation ;D
I vaguely remember it was 1mm per week or 1 cm per month :-/ ... depending on how thick it is.swehjo said:Maybe we should have mentioned earlier :
.
But it's not really unsightly when it stands as it is with the warm gray color of the plaster. Becomes a bit lighter as it dries
.Congratulations Lurvnos! Fortune favors the brave ....
I actually think it's much easier to plaster than to nail drywall and sand/tape/spackle them for what seems like eternity. Plaster should also look like plaster so you won't cry if the craftsmanship shows
.I left a thumbprint in my wall plaster just for fun and slightly regret not pressing my whole palm instead - as a kind of signature on the artwork ;D.
gaia
Again, many thanks for all the cheerful encouragement, tips, and advice
Waiting to be able to paint is no problem, it won't be until summer.
Here are some pictures:
http://web.telia.com/~u19511076/bilder/mur/mur1.jpg
The hole to the left of the wall used to be a sealed door, with a row of cabinets in front.
I want to open up the floor plan for heat distribution and general comfort. And make it possible to get an air/air heat pump.
On the right edge of the wall, there was a fire-retardant brick wall that was part of the hallway wall, it has been torn down, only the timber frame remains.
http://web.telia.com/~u19511076/bilder/mur/mur3.jpg
Seen from the hallway, the hole to the right of the post was the fire-retardant wall. The post will be replaced by a steel beam next to the wall so I get a big opening between the hallway and the kitchen.
The post in the previous picture will also be replaced by an iron beam.
http://web.telia.com/~u19511076/bilder/mur/mur2.jpg
This is how far I've come so far. The openings have been filled in, the roughest unevenness patched. Also started working on the surface. Many angles and corners, nailing a board and plastering against it. The iron beam will be housed in the corner I created.
Waiting to be able to paint is no problem, it won't be until summer.
Here are some pictures:
http://web.telia.com/~u19511076/bilder/mur/mur1.jpg
The hole to the left of the wall used to be a sealed door, with a row of cabinets in front.
I want to open up the floor plan for heat distribution and general comfort. And make it possible to get an air/air heat pump.
On the right edge of the wall, there was a fire-retardant brick wall that was part of the hallway wall, it has been torn down, only the timber frame remains.
http://web.telia.com/~u19511076/bilder/mur/mur3.jpg
Seen from the hallway, the hole to the right of the post was the fire-retardant wall. The post will be replaced by a steel beam next to the wall so I get a big opening between the hallway and the kitchen.
The post in the previous picture will also be replaced by an iron beam.
http://web.telia.com/~u19511076/bilder/mur/mur2.jpg
This is how far I've come so far. The openings have been filled in, the roughest unevenness patched. Also started working on the surface. Many angles and corners, nailing a board and plastering against it. The iron beam will be housed in the corner I created.