I’ve built a sauna from a shottily modified kit of parts, which (in conjunction with my limited diy-skillset) has led to gaps between wall panels and the roof panel. See photos.
I’m wondering what the best way is to fill these up. I assume the answer is some form of expandable foam spray, but I found surprisingly little information about this application (opposed to insulation the whole sauna with foam insulation).
Thank you!
I can’t help but I like how you resorted to asking the entire Finnish nation to help you solve this instead of a carpenter
If you see daylight through the interior paneling then you’ve built the whole thing incorrectly. You’re supposed to have a layer of foil covered insulation behind the paneling, and behind that the actual structural wall.
So I guess build a building around your sauna?
I would tear it down and build it again. Check out /r/sauna for some directions
Sauna doesn’t need to be a preasure pot. Just make sure you have some air intakes near floor level and big enough kiuas and you’re set. Heat does not magically disapear from the holes that size and after all you should be feeding the kiuas time to time with water anyways. Secret for good sauna is fresh air.
You built a shed not a sauna. Hire someone to build it.
Moss
Ok ok, I’ve built 3 saunas. Two out of uncut logs and one premade kit. If you’re located in Finland I could come take a look and fix it over the weekend.
Edit: some airflow in a sauna is always good, what I’ve always done is I’ve made an small adjustable ”window” into the same wall where kiuas is located but opposite upper corner of kiuas and to the second log sauna I left a small ~1cm gap under the door so it gets fresh air into the sauna.
Gap between the roof and wall can be easily fixed with trim pieces. Corners also with trim. I wouldn’t use sprayfoam, it can be a potential health risk.
Moss is an easy and accesable way 🙂
Nail strips of wood outside or inside to cover the cracks.
It’s fine. Some air leak just makes the löyly better in an outside sauna.
Thanks everyone. Just to clarify – the sauna is properly vented (in-vent below heater, out-vent at roof level on other side), so these additional gaps are certainly not needed/desirable.
​
Appreciate all the pointers! Will be scavenging moss, hah
First you need to build a frame and cover it with roofing and outer siding like planks. Then you put aluminum foil on the inside for vapor barrier and IR reflection. Then nail Wood panel to the supporting Rail. Remember to take care of fresh Air ventilation with adjustable valve. If you use Wood burning kiuas then that usually Will function as ventilation taken that the sauna is not Air tight.
Put insulation material into the gaps. Moss or felt fabric can work, but my family used fiber material ‘[lindrev](https://norrlandseko.se/produkt/lindrev-isolering/)’ – I guess, it is linden wood fiber? This is to ensure warmth.
Then it is a good idea to cover walls with an extra water proofing layer. We used bitumenous waterproofing material designed for roofs. Then we added another layer of planks, but this is optional.
throw more löyly
Where is the insulation?
Sikaflex 221
**TAR**
Caulk with hemp fiber. Old traditional way used for boats, floors etc.
Uretaani vaahto could work
Did you just buy sauna from walmart?
I’m assuming the kiuas uses wood and the fireplace of it has a pipe leading the smoke outside. So you are not planning to inhale the smoke and have a sad death?
You can try to fill the gaps with flax fiber thermal insulation band or something similar.
The cost effective solution is tabloid paper.
I hope this isn’t a permanent structure, because mold is looking at this rubbing its hands together and going “it’s free real estate”
Build a new one, properly this time.
Not necessarily a big problem. This will allow more air flow in the sauna, which will make the löyly better. You will have to use more heating, though.
Sen minkä mitta heittää kitti peittää rääh kjäh (work man humors)
Polyurethane foam 💪🏾😎 and silicone sealant 💪🏽😎
Stick some sammal in there, thats what they do to log house gaps.
Slight ventilation is only good
Nah. No need to fill those gaps. Best löyly is when air moves and is fresh.
Se siitä saunanteosta
I would heat that up couple of times and see how much of a problem the escaping air really is. Getting the wood wet and dry, warm and cold, few times will also help the wood settle to right places. Then it is combination of take that beam that is 5 fucking centimetres too low on one end out and but it back to its correct place, but more tightly, and adding stuffing and trimming beams.
I myself prefer more that löyly comes and goes “fast”. Thats why i wouldn’t do anything for these holes. But this is only who prefers and what question.
Make a bigger fire.
Just more water to the kiuas. If you can still sit there, it is not hot enough. Add wood. Repeat several times and gaps are gone
Eh, I don’t see the problem. We have a “temporary” sauna at our cabin made out of tiny logs, tarps and felt and the löyly is just fine
That looks bad. You can see daylight, no steam barrier, etc… That’s going to rot fast.
You need to call masi he can fix it (professional builderman). 
Step 1. Learn how to properly install tongue and groove.
In all seriousness, this is due to the (partially) incorrect installation of the type of wood that is used. The tongue and groove boards should be fully attached into a sheet the size and shape of the wall, with trim placed around the edges. Also the tongue and groove should only form the inner layer of the sauna. There should be insulation and tar paper or similar on the outside of the paneling, with another outer layer of exterior lumber (pressure treated siding is made for this) outside of that.
Throw more löyly on kiuas. Kiuas will be happy. You will be happy. Finland will be happy.
Sikaflex. Well thats worst build sauna iv ever seen
Use moss
Either build over the gaps with for example extra panes or just use a silicon paste that endures heat. Go to a local hardware store and ask.
If you want to do it properly then you need to build a wall foundation, then use tinfoil covered polyurethane walls that you put inside the foundation. Then cover both sides with panes. Remember to use varnish that is suitable for sauna, so the wall panels endure the heat. Also use different panes for the outside that are designed for exterior use.
I drew a quick picture of what a wall could be etc.
46 comments
Hello Finns,
Asking you for obvious reasons.
I’ve built a sauna from a shottily modified kit of parts, which (in conjunction with my limited diy-skillset) has led to gaps between wall panels and the roof panel. See photos.
I’m wondering what the best way is to fill these up. I assume the answer is some form of expandable foam spray, but I found surprisingly little information about this application (opposed to insulation the whole sauna with foam insulation).
Thank you!
I can’t help but I like how you resorted to asking the entire Finnish nation to help you solve this instead of a carpenter
If you see daylight through the interior paneling then you’ve built the whole thing incorrectly. You’re supposed to have a layer of foil covered insulation behind the paneling, and behind that the actual structural wall.
So I guess build a building around your sauna?
I would tear it down and build it again. Check out /r/sauna for some directions
Sauna doesn’t need to be a preasure pot. Just make sure you have some air intakes near floor level and big enough kiuas and you’re set. Heat does not magically disapear from the holes that size and after all you should be feeding the kiuas time to time with water anyways. Secret for good sauna is fresh air.
You built a shed not a sauna. Hire someone to build it.
Moss
Ok ok, I’ve built 3 saunas. Two out of uncut logs and one premade kit. If you’re located in Finland I could come take a look and fix it over the weekend.
Edit: some airflow in a sauna is always good, what I’ve always done is I’ve made an small adjustable ”window” into the same wall where kiuas is located but opposite upper corner of kiuas and to the second log sauna I left a small ~1cm gap under the door so it gets fresh air into the sauna.
Gap between the roof and wall can be easily fixed with trim pieces. Corners also with trim. I wouldn’t use sprayfoam, it can be a potential health risk.
Moss is an easy and accesable way 🙂
Nail strips of wood outside or inside to cover the cracks.
It’s fine. Some air leak just makes the löyly better in an outside sauna.
Thanks everyone. Just to clarify – the sauna is properly vented (in-vent below heater, out-vent at roof level on other side), so these additional gaps are certainly not needed/desirable.
​
Appreciate all the pointers! Will be scavenging moss, hah
It could be worse.
https://youtu.be/dkCmckWal2o
First you need to build a frame and cover it with roofing and outer siding like planks. Then you put aluminum foil on the inside for vapor barrier and IR reflection. Then nail Wood panel to the supporting Rail. Remember to take care of fresh Air ventilation with adjustable valve. If you use Wood burning kiuas then that usually Will function as ventilation taken that the sauna is not Air tight.
Put insulation material into the gaps. Moss or felt fabric can work, but my family used fiber material ‘[lindrev](https://norrlandseko.se/produkt/lindrev-isolering/)’ – I guess, it is linden wood fiber? This is to ensure warmth.
Then it is a good idea to cover walls with an extra water proofing layer. We used bitumenous waterproofing material designed for roofs. Then we added another layer of planks, but this is optional.
throw more löyly
Where is the insulation?
Sikaflex 221
**TAR**
Caulk with hemp fiber. Old traditional way used for boats, floors etc.
Uretaani vaahto could work
Did you just buy sauna from walmart?
I’m assuming the kiuas uses wood and the fireplace of it has a pipe leading the smoke outside. So you are not planning to inhale the smoke and have a sad death?
You can try to fill the gaps with flax fiber thermal insulation band or something similar.
The cost effective solution is tabloid paper.
I hope this isn’t a permanent structure, because mold is looking at this rubbing its hands together and going “it’s free real estate”
Build a new one, properly this time.
Not necessarily a big problem. This will allow more air flow in the sauna, which will make the löyly better. You will have to use more heating, though.
​
https://preview.redd.it/ekq3m03lywta1.jpeg?width=3024&format=pjpg&auto=webp&v=enabled&s=5b014368599e6e924dc9018a04bc7c7da894dd15
​
https://preview.redd.it/kaoq3gmqywta1.jpeg?width=3024&format=pjpg&auto=webp&v=enabled&s=c5cc176631a92de4f576712d15ca533089db34b6
Sen minkä mitta heittää kitti peittää rääh kjäh (work man humors)
Polyurethane foam 💪🏾😎 and silicone sealant 💪🏽😎
Stick some sammal in there, thats what they do to log house gaps.
Slight ventilation is only good
Nah. No need to fill those gaps. Best löyly is when air moves and is fresh.
Se siitä saunanteosta
I would heat that up couple of times and see how much of a problem the escaping air really is. Getting the wood wet and dry, warm and cold, few times will also help the wood settle to right places. Then it is combination of take that beam that is 5 fucking centimetres too low on one end out and but it back to its correct place, but more tightly, and adding stuffing and trimming beams.
I myself prefer more that löyly comes and goes “fast”. Thats why i wouldn’t do anything for these holes. But this is only who prefers and what question.
Make a bigger fire.
Just more water to the kiuas. If you can still sit there, it is not hot enough. Add wood. Repeat several times and gaps are gone
Eh, I don’t see the problem. We have a “temporary” sauna at our cabin made out of tiny logs, tarps and felt and the löyly is just fine
That looks bad. You can see daylight, no steam barrier, etc… That’s going to rot fast.
You need to call masi he can fix it (professional builderman). 
Step 1. Learn how to properly install tongue and groove.
In all seriousness, this is due to the (partially) incorrect installation of the type of wood that is used. The tongue and groove boards should be fully attached into a sheet the size and shape of the wall, with trim placed around the edges. Also the tongue and groove should only form the inner layer of the sauna. There should be insulation and tar paper or similar on the outside of the paneling, with another outer layer of exterior lumber (pressure treated siding is made for this) outside of that.
Throw more löyly on kiuas. Kiuas will be happy. You will be happy. Finland will be happy.
Sikaflex. Well thats worst build sauna iv ever seen
Use moss
Either build over the gaps with for example extra panes or just use a silicon paste that endures heat. Go to a local hardware store and ask.
If you want to do it properly then you need to build a wall foundation, then use tinfoil covered polyurethane walls that you put inside the foundation. Then cover both sides with panes. Remember to use varnish that is suitable for sauna, so the wall panels endure the heat. Also use different panes for the outside that are designed for exterior use.
I drew a quick picture of what a wall could be etc.
https://preview.redd.it/filh9fwd42ua1.png?width=3024&format=png&auto=webp&v=enabled&s=c0c0d9bced89e80730a3dc4c61a01bb2518d04b1