Hello all, this is my first ever post on Permies!!
Although I've read other articles about natural wood treatments, I would like to ask about a few extra details.
Here are the photos of my barn, here in the Gauja National Park, Latvia. I intend to insulate these walls from the inside with blow-in cellulose fiber, or possibly saw dust mixed with lime and sand (a traditional method here in Latvia).
Therefore I need to make sure my walls are really good and waterproof.
I've already installed a gutter along the back edge of the roof, overhanging this wall, and since it faces north, it shouldn't receive too much weather. But I need to be sure it will stay really dry to preserve my precious insulation!
I imagine most people would be thinking linseed oil - I am a little confused about boiled or non-boiled.
Also - I've been reading about how lime (whitewash) used to be used as a good exterior wood preservative, and I imagine it has some degree of water resistance too?
Some of the wooden boards are also slightly cracked (see photo) and some don't seal on the overlap perfectly. My friend recommended sealing any cracks or gaps with a cob, or lime mortar kind of mix as a natural solution.
What do you guys think? I'd really appreciate any input, thank you!!
I don't know about the finishes at all but I'm sure those experts will be along shortly.
I have a couple thoughts about the cracks. I think I've heard that the ideal way to install board and batten siding is to fasten the boards (wider ones that are underneath) and the battens (little ones that cover the gaps) with screws or nails in or near the center of the board. Then all the wood pieces can shrink and expand and the fasteners won't cause the boards to split. It's hard to see the fasteners in your pictures but I think that could be the cause of the splits. So, you might be able to pull the nails/screws, replace any split boards and refasten them all the center and then your insulation should be better protected for years to come.
A second thing I noticed is that rainwater is splashing off the ground and hitting the bottom 1/2 meter of your siding. This may cause it to rot faster (or penetrate little cracks easier). Adding the gutters should help that a lot. I'm not sure of other fixes that could work. My log home building friend says to keep all logs and wood siding at least 18" off the ground to avoid splashing issues.
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Boiled linseed oil includes additives to get it to dry faster (12-24 hours. Natural linseed oil takes a few days to dry. I'm using linseed oil to protect the timbers on my timber frame.
As for lime washing, during the Appropriate Technology Course (ATC) at Wheaton labs we applied lime wash to a building with wood siding. It takes several coats but is easy to apply. I'd be interested to hear how that's holding up.
I'm with Mike, I would replace the cracked battens before applying your finish.