Replace pressure-treated sill from 1951?

[Oldfart]

An old auxiliary building from 1951 will get a new facade and insulation. Presumably, it was originally built with a foundation wall and a framed floor, but was later filled in with concrete. It's likely that both a vapor barrier and insulation under the slab are missing, but I hope there is at least a capillary-breaking layer. The sill appears to be pressure-treated and partially painted. Moisture content measurement indicates no problems.

The walls previously consisted of a frame of logs with one-inch facade planks, an air gap, trätex, and interior paneling. The logs are spaced 3-5 meters apart, so I suspect that the panel boards are partially load-bearing and stabilizing. The idea is to instead create a modern frame with 195x45 mm and then horizontally frame with 45 mm on the inside to get overlapping joints in the insulation. Wind barrier, air gap, and batten panel on the outside. Vapor barrier, plywood, and gypsum on the inside. Alternatively, cellulose insulation, plywood, and no gypsum boards, i.e., a completely hygroscopic construction instead.

Should I replace the sill while I'm at it, as I don't want to build in an odor problem, or am I worrying too much? Has the sill stabilized over 70 years, or does it still emit enough to become an issue?

 

[tompax]

An old auxiliary building from 1951 is set to get a new facade and insulation. Presumably, it was originally built with a foundation wall and framed floor, but later concreted again. Presumably, both a vapor barrier and insulation are missing under the slab, but I hope there is at least a capillary-breaking layer. The sill appears to be pressure-treated and partially painted. Moisture content measurement indicates no problems.

The walls previously consisted of a frame of logs with one-inch facade boards, air gap, trätex, interior panel. The logs are spaced 3-5 meters apart so I suspect that the panel boards are partially load-bearing and stabilizing. The idea is to instead make a modern frame in 195x45 mm and then horizontally frame with 45mm on the inside to get overlapping joints in the insulation. Wind paper, air gap, and board-and-batten siding on the outside. Vapor barrier, plywood, and gypsum on the inside. Alternatively, cellulose insulation, plywood, and no gypsum boards, i.e., a completely hygroscopic construction instead.

Should I replace the sill while I'm at it, I don't want to build in a smell problem, or am I worrying too much? Has the sill stabilized over 70 years or is it still emitting enough to be a problem?

It can be a hell of a job to replace the sill. I probably wouldn’t have attempted it if there were no problems with the old one, even though it is pressure-treated.

What is the building used for?

 

[Oldfart]

What is the building used for?

It is four by ten meters, unheated and used as a carpentry workshop and storage. With heating and insulation, the idea is that it will be a bit nicer to work there in the winter.

 

[Jonatan79]

Sounds like a lot of work for little... How big is the building? Pictures?

 

[tompax]

It is four by ten meters, unheated, and used as a workshop and storage. With heating and insulation, the idea is that it will be a bit nicer to work there in the winter.

Then I recommend you keep the sill. The sill is not directly connected to the interior either, and if you mean that it is dry and nice and no elevated moisture levels, it means it is doing well in there.

There is absolutely no reason to expend a lot of energy on replacing it. It is an enormous job. Completely unnecessary in this case, I think. I personally have installed double sills on a garage building, the lower one pressure-treated, the upper one as part of the non-treated frame. It works excellently to this day. As long as it isn't wet, there are no problems at all.

Hope this can save you some headache, time, and money!

I don't think you'll get better advice than this Good luck with the build!