# Best Way to Insulate Plank Construction?



## Nealtw (Jun 22, 2017)

MKCoconuts said:


> Hello everyone, names Sean and I'm new here.
> 
> A quick background, bought my first house back in June of '18. Nice 3-4 bedroom, 1.5 bath 2 story with 2 stall garage on .28 acres. I got a good deal for the amount of room it provides.
> 
> ...


 Your best bet is to build a 2x4 wall inside that wall just for insulation, just like you would do if it was a brick house.


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## MKCoconuts (Jan 27, 2019)

Nealtw said:


> Your best bet is to build a 2x4 wall inside that wall just for insulation, just like you would do if it was a brick house.


Are you saying leave the planking in place and build the 2x4 right against it? If so, I could do that, but it'd push me about 3 inches past the window frame. 

Removing the interior plank would give me another inch. Removing both would put me near flush with the window frame. But from the looks of it, both sets of planks are load bearing, but with finding such little info on this construction, I am not 100 percent sure.


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## Nealtw (Jun 22, 2017)

MKCoconuts said:


> Are you saying leave the planking in place and build the 2x4 right against it? If so, I could do that, but it'd push me about 3 inches past the window frame.
> 
> Removing the interior plank would give me another inch. Removing both would put me near flush with the window frame. But from the looks of it, both sets of planks are load bearing, but with finding such little info on this construction, I am not 100 percent sure.


 Plank construction that I have seen, has the planks from the foundation to the roof, you wouldn't remove either of them. You would deal with doors and windows just like a brick house or a basement with windows.


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## Bud9051 (Nov 11, 2015)

I've never heard the term or seen that style of construction, so I did some searching but really didn't find the term "double plank construction". Any chance of some pictures?

My concern would be what is supporting the house? Part of what I read talked about the plank construction is the framing. If so I would do as Neal suggests, build your 2x4 frame to the inside and add extensions for doors and windows.

Before I do more guessing I'll wait to see if we can get some pictures.
*Here's* a thread with guidance for inserting pictures.

Bud


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## Nealtw (Jun 22, 2017)




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## MKCoconuts (Jan 27, 2019)

Here's some pictures. They do not run from foundation to the roof as far as I can tell. I did pull one of the inside one's out before realizing what I was dealing with. I have thought about leaving them in place and use rigid foam to insulate with drywall over top. Downside is I don't believe of a way I can add any electrical outlets to the wall.


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## Nealtw (Jun 22, 2017)

MKCoconuts said:


> Here's some pictures. They do not run from foundation to the roof as far as I can tell. I did pull one of the inside one's out before realizing what I was dealing with. I have thought about leaving them in place and use rigid foam to insulate with drywall over top. Downside is I don't believe of a way I can add any electrical outlets to the wall.
> 
> 
> 
> ...


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## MKCoconuts (Jan 27, 2019)

Nealtw said:


> MKCoconuts said:
> 
> 
> > How thick are the inside board. , what does the outside look like? It does look like it is much like a timber frame with fillers.
> ...


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## Nealtw (Jun 22, 2017)

MKCoconuts said:


> Nealtw said:
> 
> 
> > Inside are ~1 1/8 thick. Outside are ~1 3/4 thick.
> ...


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## Bud9051 (Nov 11, 2015)

Just opinion here as I'm not familiar with this method at all. However, I would consider removing any of the planks as being high risk. We just don't know what is holding this house up. I've removed plaster and lathe and discovered it was helping to strengthen the walls.

Now, I hate to mention building codes on a house of this vintage but different locations have different rules. In a cold climate you might be required to meet some minimal amount of insulation when done. Using just rigid foam would take up to 4" for r-20 and the cost would be significant. Jam extensions for windows and doors are done all the time and then your electrical and insulation become easier. Electrical and plumbing may need permits as well.

Good luck but I'll leave the advice to Neal

Bud


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## MKCoconuts (Jan 27, 2019)

Nealtw said:


> So if you were to remove it all you would be stripping the outside too?
> Even if they are just filler in a timber frame, something or some of them are bearing the timber above.
> Are they sitting on a timber too?
> Old lumber like that may have some value.


If I were [able] to remove it all, yes, I would be stripping to the outside. After taking a second look with some better light, it does appear the outside planks "may" run the entire height of the house. It is hard to tell, but they run past what I believe to be the bottom plate for the inside planks. 

So from looking at it as if it were a modern framed wall, it would appear there is a bottom and top plate and the inside planks are the "studs". At least, it appears that way.


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## MKCoconuts (Jan 27, 2019)

Bud9051 said:


> Just opinion here as I'm not familiar with this method at all. However, I would consider removing any of the planks as being high risk. We just don't know what is holding this house up. I've removed plaster and lathe and discovered it was helping to strengthen the walls.
> 
> Now, I hate to mention building codes on a house of this vintage but different locations have different rules. In a cold climate you might be required to meet some minimal amount of insulation when done. Using just rigid foam would take up to 4" for r-20 and the cost would be significant. Jam extensions for windows and doors are done all the time and then your electrical and insulation become easier. Electrical and plumbing may need permits as well.
> 
> ...


Building code for my area on insulation requires a minimum of R13+10 for 2x4 walls on new construction. I understand rigid foam wouldn't get me near that, but it may be the best option I have without losing space. The room is not that wide so losing a few inches will be a last resort, but may be the only way to effectively get what I want.


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## Nealtw (Jun 22, 2017)

MKCoconuts said:


> If I were [able] to remove it all, yes, I would be stripping to the outside. After taking a second look with some better light, it does appear the outside planks "may" run the entire height of the house. It is hard to tell, but they run past what I believe to be the bottom plate for the inside planks.
> 
> So from looking at it as if it were a modern framed wall, it would appear there is a bottom and top plate and the inside planks are the "studs". At least, it appears that way.


 Then I would consider removing the insides maybe 4 ft at a time and building a 2x4 wall in their place, that gives you insulation and wiring.
Jam extension for windows and doors are just details to deal with have you have drywall up.


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## MKCoconuts (Jan 27, 2019)

Here are two more photos. You can see what appears to be a bottom plate for the inner planks and can see the outer planks go past it. And and upper plate for the inner planks.

Bottom








Top








I'll have a better idea once I get that baseboard out of the way. My dad will also take a look at it because I peaked his interest when I mentioned it to him.


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## MKCoconuts (Jan 27, 2019)

Also would like to say thank you to everyone that chipped in their .02 cents. It's much appreciated for someone who will be doing changes like this room by room. Keep the info coming if you find anything. I will talk to my coworker who mentioned it tonight when I see him. I'm thinking he may have run into this when he renovated his house.


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## Windows on Wash (Aug 30, 2011)

I would definitely NOT fill anything between those two planks. You will change the way that they dry out and that could be catastrophic in the long run. I think you best bet is as was mentioned previously. A framed wall in front of the plank wall. 



I would put a thin layer of foam board that is attached to the wall and air sealed. I would thing frame the wall in front of it and fill with normal batt insulation. Wall can still dry to the exterior and the foam board will nearly totally eliminate any drying to the inside.


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## MKCoconuts (Jan 27, 2019)

Windows on Wash said:


> I would definitely NOT fill anything between those two planks. You will change the way that they dry out and that could be catastrophic in the long run. I think you best bet is as was mentioned previously. A framed wall in front of the plank wall.
> 
> 
> 
> I would put a thin layer of foam board that is attached to the wall and air sealed. I would thing frame the wall in front of it and fill with normal batt insulation. Wall can still dry to the exterior and the foam board will nearly totally eliminate any drying to the inside.


I wasn't planning on filling inbetween, exactly for the reason you mentioned. There is no rotted wood, so it is obvious that any moisture that does make it's way there doesn't stick around for long. 

I really hate putting a framed wall and losing that space, it would seem there is no other option unless someone who's an expert in this rare construction pops up and can point another direction. I am still going to explore the idea of pulling one plank at a time and installing a 2x4 in it's place. And then when time/money permits, remove the outer ones and replace them with OSB, wrap, insulation and new siding.


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## Windows on Wash (Aug 30, 2011)

Remember that the space we are talking about is about 8" of length and width respectively. To insulate the home and allow for the exterior cladding to last another lifetime, that isn't that punitive in my opinion. That said, you are definitely the boss here with regards to your own home.


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## MKCoconuts (Jan 27, 2019)

The bigger benefit to adding the frame is I have somewhere to run the electrical, as mentioned. And leaving one outlet in the room just won't do the trick. 

I may go the route you mentioned with the foam board and air sealed and then the framing with bat insulation.


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## ClarenceBauer (Mar 4, 2005)

See if you can find this magazine. OLD - HOUSE JOURNAL Vol XX1 , # 3 HOUSES WITHOUT FRAMES.
Technique of Plank Construction by Stephen B. Jordan page # 36 thru page # 41 this article should help you under plank framing.


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## MKCoconuts (Jan 27, 2019)

That was an excellent read. I can't believe that never popped up in any of my searches. It does answer a few questions and looks like I'm going to have to give up a few inches to put in insulation, which, I suppose is worth it if it helps keep the house warmer/cooler and saves some money on the energy bills. I will have to take the articles suggestion too and super insulate the attic, once all the knob and tube wiring is replaced with romex.


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## MKCoconuts (Jan 27, 2019)

So, after adding up cost of everything, I think I'd decided my plan. I'm going to put 2" rigid foam up (giving me a Rvalue of 12.9), some 1x3 furring strips to allow room for wiring and 1/2" drywall. This will require me to buy MC wire but this way will certainly warm that room up, give me the extra outlets I want, while sacrificing the least amount of space. Any one have objections or concerns with this route?


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## Nealtw (Jun 22, 2017)

MKCoconuts said:


> So, after adding up cost of everything, I think I'd decided my plan. I'm going to put 2" rigid foam up (giving me a Rvalue of 12.9), some 1x3 furring strips to allow room for wiring and 1/2" drywall. This will require me to buy MC wire but this way will certainly warm that room up, give me the extra outlets I want, while sacrificing the least amount of space. Any one have objections or concerns with this route?


 It is a strange house, pretty hard for anyone to tell you something is wrong.
:biggrin2:


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## MKCoconuts (Jan 27, 2019)

That it is. Odd enough, I am pretty sure my grandparents house is older but has normal stud walls and it's only 2 miles away! Haha. And while I do like the house, if money were no object, I'd tear it all down, dig out a full basement (right now half the house has a dirt floor basement, other half a crawlspace), and rebuild it nearly the same....just more modern and better insulated. 

I'd just like to have everything I change as close to code as possible, though with such a house, could I be considered a gray area?


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## Nealtw (Jun 22, 2017)

MKCoconuts said:


> That it is. Odd enough, I am pretty sure my grandparents house is older but has normal stud walls and it's only 2 miles away! Haha. And while I do like the house, if money were no object, I'd tear it all down, dig out a full basement (right now half the house has a dirt floor basement, other half a crawlspace), and rebuild it nearly the same....just more modern and better insulated.
> 
> I'd just like to have everything I change as close to code as possible, though with such a house, could I be considered a gray area?


Your parents house is balloon framed and there are enough around that people know the pitfalls and the few improvement that should be made but with yours, you will just have to discover them as you go. 


We did some work on a house where the whole house was built with solid 2x4s all nailed together. Electricians where making room for wires with a chain saw and we had too get a steel frame built for the HVAC register holes in the floor. 
The inspectors all just walked around, shaking there head, smiling at each little way some one figured out some way of doing something and past everything first time.


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## MKCoconuts (Jan 27, 2019)

So I got pretty far insulating with rigid foam and got the wiring figured out. I had a friend who is an architecture engineer look at it and said I would be okay taking the inner planks out and studding the wall out. 

Given that I got almost two walls done with just putting the rigid foam over the inner planks, I hate to back track. But I was wondering, does anyone see an issue if I were to remove the inner planks, put the rigid board against the outside planks (sheathing) and then stud out and use fiberglass insulation. Do so would eliminate thermal bridging and give a more proper way of running my electrical.

If I stud out, I do not want to leave the interior planks. Reason being that doing so will require me to move the current doorway over and if I can avoid that, I'd be a happy camper. It will also making window molding easier and keep the room a good size.


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## Nealtw (Jun 22, 2017)

I think the outer planks are balloon from bottom to top of the house, so they are the structure, I don't see a problem with just adding a wall instead. Much like building wall in front of a brick wall . But at best I too am just guessing at what the builders had in mind.


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## MKCoconuts (Jan 27, 2019)

I'm more concerned with using the rigid foam on the interior side of it. I don't want it cause a moisture problem and rotting the wood since, like you said, that is the supporting area of the house.

If I had the money, I'd tear this down and rebuild with modern framing almost exactly the way it is now


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## Nealtw (Jun 22, 2017)

MKCoconuts said:


> I'm more concerned with using the rigid foam on the interior side of it. I don't want it cause a moisture problem and rotting the wood since, like you said, that is the supporting area of the house.
> 
> If I had the money, I'd tear this down and rebuild with modern framing almost exactly the way it is now


 The trick is to seal the inside so no house air can get back in there. Moisture condenses at the dew point and the dew point will be somewhere in the wall so just don't let moisture get to that spot.
Air leaks that let air travel right thru the wall are the worst.


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## MKCoconuts (Jan 27, 2019)

Which the hardest parts I would suspect to be around the windows.


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## Nealtw (Jun 22, 2017)

MKCoconuts said:


> Which the hardest parts I would suspect to be around the windows.


 with old windows yes. New installation methods help a lot.


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## MKCoconuts (Jan 27, 2019)

The windows are less than five years old


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## davison0976 (Jan 5, 2019)

I wish I saw this thread earlier. Not that it would necessarily change anything of course.


I would hang on to every existing plank in this house for dear life. That wood is invaluable and I am sure came from mature trees making them priceless in terms of both originality and durability both structural and in terms of weather resistance. Plus, what an eco-friendly construction being all natural, no glues or other petroleum or polymeric materials.


Anyway, I would insulate from an outside. Would throw away vinyl siding. Wrap a weather barrier like Tyvek around. Then 4" total of Rockwool comfortboard 80 (R4 per inch) insulation. Then either acrylic stucco or furring strips and either cedar shingles or fiber cement siding. The remaining R value would come from the existing wall structure.


Could substitute mineral wool insulation with XPS, also outside. But not ISO because its performance decreases with colder temperature.


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## MKCoconuts (Jan 27, 2019)

I can live with getting rid of the inner planks if it means having a home that has greater function and keeps me warm in cold PA winters without costing me a arm and leg. 

Insulating from the outside is not in the cards as that is something that needs done all at once. Inside I can work room by room as time and funds allow.


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## JordanWamkrr (Jan 3, 2022)

Hey man!! I was Googling insulating post and beam homes when I came across this post. Im.doing the same thing right now. I did the internal stud method on my first house. Thinking of the rigid foam method on this new project. I have learned a ton about do's and don'ts on these homes. Id like to bounce some ideas and some insight with what I found with my first house project and things ill do differently on this new one but you're probably done with your project by now.


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## jitterbugjim1 (6 mo ago)

spray foam insulation seems like the perfect application here. you can get a r-19 value with only a few inches of foam. we used it in our basement due to the joists being hand sawn actual 3x10 every 8" or so apart. my home was built in 1889


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## bronc351W (4 mo ago)

MKCoconuts said:


> So I got pretty far insulating with rigid foam and got the wiring figured out. I had a friend who is an architecture engineer look at it and said I would be okay taking the inner planks out and studding the wall out.
> 
> Given that I got almost two walls done with just putting the rigid foam over the inner planks, I hate to back track. But I was wondering, does anyone see an issue if I were to remove the inner planks, put the rigid board against the outside planks (sheathing) and then stud out and use fiberglass insulation. Do so would eliminate thermal bridging and give a more proper way of running my electrical.
> 
> If I stud out, I do not want to leave the interior planks. Reason being that doing so will require me to move the current doorway over and if I can avoid that, I'd be a happy camper. It will also making window molding easier and keep the room a good size.


I'm in PA as well an inherited my father's 2bd 1br house and have the exact same issue. Took the plaster and lath walls out and revealed planks. As you were saying your buddy acknowledged the removal of the 1st set of planks to be able to stud of a 2x4 wall? I'd love to rack your brain about the process because I myself am a bit unaware of plank style builds and wanting the same exact reasoning. More outlets then just 1 a room while coverting the 2 prong ungrounded outlets to gfci and insulate for me and the family.


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## Old Thomas (Nov 28, 2019)

On two occasions I put new siding on plank houses. They were two layers of 2 inch thick planks, from about 8 to 14 inches wide, installed vertically with their gaps overlapped. The planks were the full 2 story height in length, one piece all the way. I removed the original siding and used Tyvek and 3/4” tongue and groove styrofoam behind the siding. Wood provides some insulation value depending on species, with softwood being perhaps R-3 to R-6 for 4 inches of thickness. I added another R-4 and an air barrier. There are a lot of cracks and knot holes in plank construction so your main objective is to keep the wind from blowing through. If it were mine I would use foil faced foam inside and tape the seams. One of the houses I worked on belonged to my aunt and she said it was warm and quiet. If your attic is well insulated, your windows are good and you keep air from leaking in, sidewall insulation doesn’t have to be all that great.


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## bronc351W (4 mo ago)

Old Thomas, are you specifically speaking about insulating on the outside of the house as opposed to the inside? Like MKCocunts mentioned, that may be out of my budget. But you've mentioned the inside with foil foam&tape. When you stud infront of the foam are you still installing the proper R-rated batts?


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