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Community and Q&A

Maine built pre-1800 post & beam no insulation

b9rH4Loiws | Posted in General Questions on

you go that right. ZERO insulation. Walls are plaster/lath and plaster/ split boards. Lath work came in around 1800? so the older part (built before 1750) has no lath– just very wide boards split to accept plaster.

So what to do about insulating ? There’s no ridge so no vents there, and no soffit, no air coming through any place unless you open windows. In the attic there is a knee wall with two 10″x20″ windows. they can be removed if you want air — Exterior clapboards are over 200 years old, and dense as they are “old growth”. and in good condition, so no need to replace them. Also there are no ridge vents ( no vents at all, unless you open windows!) what? oh where to start, what to do!!)

Currently the house “breathes” because there is nothing to stop air flow.

Oh, and we are less than one mile from the Atlantic Ocean, get all the fog and have a high water table — we can’t do much about the water issues, and the house for the most part sits on granite walls and has a crawl space So humidity is generally 40% or higher…. I never have dry skin even in January!

So, Roxul? between floors is a possibility, since the house needs a fire wall and sound proofing, but what to do about the walls?

suggestions? from you who live in houses pre-1800 would be especially nice…

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  1. user-1139752 | | #1

    Hi, I have an 1840 cape. We used closed cell urethane in the walls and roof area. We stripped all the clapboards, trim and sheathing to add the urethane from the exterior. We then put back all the old material, but replaced the siding with spruce clapboards and stainless nails. The roof is a cold roof system with a 3/4" air gap from soffet to gable vent. Recently we added 2-4" of closed cell urethane to the floors. Our wood use has dropped from 7 to 2 cords. The house is fairly small at 1300 sq ft.

  2. GBA Editor
    Martin Holladay | | #2

    You didn't explain the wall and roof construction thoroughly, but I presume there are wall studs between the posts, and that these stud cavities are empty. (Not all older buildings have wall studs, so I may be wrong.)

    If you do have empty framing cavities, the usual approach is to insulate them with dense-packed cellulose. This means you'll either have to drill access holes on the interior, and later patch the holes, or you'll have to temporarily remove some of the siding to blow cellulose from the exterior.

    If you can't install cellulose, your other options are rigid foam or spray foam. Either of these options usually requires stripping either the interior finishes or the siding and roofing to gain access.

  3. dankolbert | | #3

    Yeah, there are often no great solutions in houses that old. Especially if there are still original details that you want to save on the inside or outside.

    Let me know where in Maine you are - I know good auditors/insulation contractors in various parts of the state who may be good resources for you.

  4. user-1139752 | | #4

    Here's a photo of what I did in the main part of the house. I used two layers of urethane foam with foil facing, leaving a gap to fill with canned foam. The one drawback with this is our cell phones don't work as well inside this part of the house.

  5. user-1120142 | | #5

    All of the answers provided above sound reasonable. However, I learned long ago that giving advice to questions asked at home shows was often misleading to the clients. Upon seeing their project, I often found that any advice given site unseen was inappropriate for their particular circumstances. Get a professional on site before you follow any one method for solving your problems.

  6. Expert Member
    Michael Maines | | #6

    One thing to consider is that even though the clapboards are in good condition, they are most likely not 100% watertight. The uninsulated framing bays can dry easily to the inside or out, but if you insulate you are slowing down or eliminating the potential to dry to the inside. If the exterior details are not critical to you, the best thing for the building might be exterior insulation with a WRB and new or re-installed cladding.

  7. user-1139723 | | #7

    We fall under the "California code" here in Maine. (took effect 12/2011) We are not going to be able to use cellulose or any spray foam due to fire code regulations, of the town. Still need input as to the use of Roxul or rock wool. The Answer our contractor has found to be the most helpful is from Michael Maines, which is what we are looking at. The issues of the spray foam and other insualtional factors mentioned will not meet the code issues of this building. Please keep the comments coming, everything has been interesting. thank you.

  8. wjrobinson | | #8

    Haven't done it, but Roxul seems like a solution for you.

  9. albertrooks | | #9


    Mineral Wool is a good solution for adding exterior insulation.

    Some suggest placing a WRB at the interior sheathing behind the MW. And others suggest adding an additional one at the face of the MW behind the battens. Both are reasonable options. Placing one at the interior of the MW allows easier connection to window and doors for air and weather sealing.

    Installing MW is getting as easy as installing foam boards. Installation video here: In some respects MW is a "safer layer" than foam boards since the layers can dry as they need to in the event of defects.

  10. Expert Member
    Michael Maines | | #10

    Oldhouse, where in Maine are you? I live in Portland and work at a design/build firm in Freeport, so I'm quite familiar with MUBEC but have not heard it called "the California Code." I also have not heard of towns that don't allow cellulose or spray foam--that's an ignorant stance unless you mean uncovered insulation.

    We worked on a similar project in Yarmouth where the owner did not allow us to touch the outside of the building. We ended up installing Roxul in the stud bays.

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