Replacing siding and insulation on a wood frame house

Hi!

I have two traditional wood frame houses on stack stone and cement foundations that need to be restored.  The siding and insulation needs to be replaced.  I would love to put cob in the frame and finish the exterior plaster.  Do I need a moisture barrier so the cob does not affect the drywall on the interior (which is still in good condition)?  What to do about wiring?  Would I need to rewire everything in conduits?

I live in very dry southern Arizona with the exception of monsoons.

Is this practical?  I have a lot of earth that is heavy in clay and I can harvest invasive Tamarisk/Salt Cedar from the area.

Gratitude in Advance!!!

Jen

I would just do the cob walls and get rid of all boards outside and inside - drywall. You would have natural walls and with right finish - beautiful look.
You could put wiring in flexible conduit or directly within the cob. Conduit will allow you to work on it later, so you would not mess with clay and wires and the same time. You could also form grooves in a wet cob, during the build. Or you could buy a chaser and chase the cob walls for the wires. If you go the chaser route, make sure you connect it to an efficient vacuum cleaner and wear good respirator mask.
I used the chaser on my CEB walls.

Thank you!

I was going to keep the drywall because the house is already finished on the inside and hauling the drywall in multiple 6 hour trips to a landfill was not an exciting prospect.  

If I did keep the drywall in place, is there a moisture barrier you would recommend?   Do I need to add any wire mesh to keep the cob intact within the framing?  I am trying to find a good video where someone does this type of remodel...but I have not found anything so far.

Jen

Jen,

I don't know much about any plastic barriers. My philosophy is - humans did not use them for 10000 years so it can be built without them. However drywall is a recent invention so you have to ask someone who knows more about it.

To prevent mold and to protect the drywall from being damaged, a moisture barrier would be good.  If you are against using plastic, the moisture barrier could be metal or glass.

I watch a house being build with adobe. This was a tradition home with drywall.

Chicken wire was used to put the adobe exterior walls.

That might be a way to easily add cob.

Anne,

They built the adobe walls around the house or they just plastered on the outside on the chicken wire?

Hi Jen,

Since cob is a poor insulator you need pretty thick walls (like 1-2 feet) to get enough thermal mass for a cob wall to really be effective. So you would probably need to furr out your 2x4 or 2x6 and extend the perimeter of your foundation.

Protecting the existing drywall is kind of a Catch-22. On one hand it would need to protected from the moisture of the cob during construction to prevent it getting moldy. But then you want the wall to be vapor permeable when its complete so moisture doesn't become trapped in the wall. House wrap is supposed to be water resistant yet vapor permeable so that would probably be your best bet.

If you like the aesthetic of cob I think I would insulate the stud bays with something like wool or rock wool batts and then do a lath and lime plaster finish on the exterior. It would look like cob but without having to make any changes to the wall system or mess with the the electrical.      

Cristobal Cristo wrote:Anne,

They built the adobe walls around the house or they just plastered on the outside on the chicken wire?

They put the adobe on to the chicken wire like you would do cob or plaster.  These were not bricks.

When finished the houses looked much like the plaster homes from the 1920s.  

Then the homes were painted.

have had a lot of experience with these types of building, but I would need to see photos of the current situation to start with.
Some exterior shots, of bare timber frame, frame to foundation connection at least.

Sounds like a cool idea but certainly think posting some pictures would be helpful to show the permies forum folks exactly what it looks like. Cob is breathable so it could certainly have moisture pass through it to the drywall so that's for sure a concern.  I'm in a place called Crestone, CO which is pretty high and dry but still think about moisture while building. I have a YouTube channel called Owner Builders Unite and we have a few videos with working with Adobe, cob, and earthen plasters incase you're interested... again would love to see some pics!

https://www.youtube.com/@OwnerBuildersUnite/featured

Re: Cristobal Cristo ,
Dec 06, 2024 12:12:32
Putting drywall inside a cob house acts like insulation, helps molds to flourish. Don't do it.

Marek Mraz wrote:Putting drywall inside a cob house acts like insulation, helps molds to flourish.

I reccomded to remove drywall from the inside, not install it.