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I have an old prefab cottage made of wood.

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its walls have become leaky. When it rains sideways (happens a lot because we're so close to the sea), water seeps in from in between the beams, and through the knotholes.

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This is, of course, ruining the wood inside and I need to do something.

The weather conditions here are extreme: in summer, there is zero rain, and temperatures can reach up to 40°C (104°F). In winter, there are rare but intense rainfalls. I guess the nearby sea makes the air very salty.

I have considered - and discarded - a number of options, but of course I'm open to being corrected! I am really out of my depth here.

  • Varnish it - the most obvious solution I guess, and would take care of the leaks, but that'd have to be sanded down every couple years, right? I'd like to avoid that as it would be a lot of work. Especially since with our extreme weather, the cycle is going to be very short.

  • Use silicone to fix the leaks directly - I've been told that might not hold together well, and silicone that can withstand the sun is extremely expensive around here. It could be hundreds of Euros to do the job.

  • Plaster the walls - an interesting option as it would also add a little bit of insulation (it gets mercilessly hot in the cottage during the summer), but I've never done this before, it seems tough to do and it would of course alter the look of the building.

Obviously, I'd like the solution to be as cheap as possible, and as long-lasting as possible.

What would you do?

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Try not to go too cheap - if you do this right you may save a lot on not having to sort out dehumidification off-grid, as I assume this is the same building, and if you fix the walls getting wet you won't need that, or at least not nearly as much of it. What dehumidification options don't require a lot of electricity?

Unless you have a great desire to preserve the exterior look, I'd strongly consider wrapping another layer around this - whether it's "plastering" "stuccoing" "rendering" "Exterior Insulation and Finish System" (high-tech stucco with more insulation) or just framing up a new wooden wall level with or just past the ends of the interlocking wall logs. If going with wood framing, be sure place an air barrier ("housewrap") below the new siding layer that will block liquid water but permit vapor to pass.

Look up "Larsen truss" for one relatively low-cost and DIY friendly method of framing a new insulation cavity and non-structural (not holding the roof up) wall onto an existing structural wall.

Or you could just shingle it - traditional (and durable/effective, thus the tradition) for seaside houses around here, but you may have difficulty finding cedar shingles in your local area...is there such a thing as wall tile like the roofing tiles a that are more common there than here? Or perhaps you get shiploads of cedar shingles from Canada?

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    I think you may have struck gold with the idea of shingling the cabin. That would certainly keep the outside looking rustic and wooden, while also keeping out the driving rain. On the east coast of the US this is also common and highly effective. – BrownRedHawk Mar 9 '15 at 15:22
  • IF Pekka can get the materials in the Canary Islands (without excessive expense.) – Ecnerwal Mar 9 '15 at 15:29
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Well, you could try something like a log home chinking material.

These obviously aren't logs and it might be harder to use backing rods in the relatively tight chink joints, but I would still think that you'd want a flexible seal in the joints.

You did say the water is coming in through the joints and knot holes, right? It obviously isn't seeping all the way in through the core of the wood.

I think you might want to look into using a preservative (borate based?) and some kind of sealer on the wood as well. Particularly the ends which are naturally more absorbent, to protect it from that severe weather and from boring insects.

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Residing the outside would be you best long term fix. It will not be the cheapest, just the most durable WHEN DONE RIGHT. You will need to leave the corners as they are, they are a structural part of the building, if they are removed the corners will separate, and down comes the house. The plaster you mentioned, for me the system that comes to mind to me is "EIFS" it is a modern day plaster/stucco replacement. Why that came to mind is that a lot of installs are done with a 2" layer of Styrofoam under it.

Horizontal wood siding is another alternative, but the corners will have to be dealt with in a way so that they are covered too. Just that is a major leak area.

Caulking may do it too, but the wood will need to be cleaned to insure the caulk bonds well. Seasonal changes should not allow the wood to expand and contract the way other houses do since all your sides are stacked like a log home. The WHOLE house shrinks and expands together, so the gaps between the wood in the walls barely change, just the height of the wall, from wet season to dry season. I would suggest using a polyurethane caulk, maybe even with a primer to insure the caulk bonds to the wood well. You must be certain the caulk adheres well to the surfaces, for caulk improperly placed can hold in water, as well as good practices of caulking keep it out.

  • Who said anything about chopping off the ends? ;-) – Craig Mar 8 '15 at 20:51
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    I would hope nobody does. A siding installer may see them as "in the way" and may want to remove them to make his job easier. Stranger things have happened. – Jack Mar 8 '15 at 21:01
  • That's a good point. – Craig Mar 8 '15 at 21:02
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Some good suggestions here for you to ponder, Pekka. Looking at that stack of pallets in front of the house, I'm wondering if they're serving as a foundation for the structure (in addition to being a porch)? If that is the case, I would probably not go the plaster route. Plaster, chinking, or something along those lines would be the easiest and most cost effective, but if your house is sitting on pallets it likely moves around a fair bit over the course of 4 seasons, which would make any kind of plaster/stucco crack quite badly. Just my 2 cents. If you were going to do siding, maybe you could find some nice cedar-type lumber to do vertical lap or T&G, and as folks mention, insulate the walls some. Though, if you are going to insulate, the top of the building envelope should be addressed first. Good luck!

brett

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I have the exact same issue with a new chalet of identical construction. I'd say start by caulking the end crosses vertically. Clean the exterior and apply two coats of pine tar vitriol (pre-thinned with gum turpentine). Apply on a warm day and allow 2 or 3 days before the second coat. You could use another pine tar product if you prefer a different colour but it would likely require thinning with linseed oil for application and absorption into the wood. Clean the wood first with linseed oil soap, you could even prime with a coat of linseed prior to pine tar application.

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