Norwegian Style Siding

My friend Carlos Martinez suggested that I use 3/8" plywood strapping to attach the siding the house. First install the tyvek with minmal staples Rip 4x8 sheets of 3/8" plywood on the table saw to about 2" wide. Align the strips vertically and use a roofing nailer with 1-1/2" nails to nail them to the stud (through the tyvek). This method has the additional benefit of preserving the tyvek in high winds if siding is not immediately installed. I've seen so many cabins and houses on the Kenai Peninsula with tyvek that has blown off. Once you are ready to install the siding, simply align the nail holes over the plywood straps. This also helps to locate the studs.

Why do this? The Norwegians used to do this on their houses, especially in wet, cold climates. No, of course they didn't use 3/8ths plywood, they used small dimensional lumber. Proper ventilation is even more important in these climates. The air gap formed by the strapping behind the siding forms an air channel for moisture to escape. Otherwise, it has the tendency to condense within or behind the siding.An article in Fine Homebuilding described how the author had repainted his wooden lap siding and it kept blistering. The blisters had water in them. He couldn't figure out where the water was coming from. Many people do not realize that water can attack a structure from not only the outside, but from inside as well. This is the reason for a vapor barrier, and the reason tyvek was invented. A non-permeable membrane such as polyethelyene sheeting absolutely must not be used for an outer barrier. This would trap moisture in the framing. Tyvek allows the moisture to escape due to very small holes which allow water vapor to escape, yet does not allow liquid water to penetrate. If you've ever gone skiing and taken off your jacket in still air in the sunlight, you have seen water vapor. Anway, condensation occurs when this vapor transits from a warm side to cold side of an insulating medium. Usually it forms on the colder side of the insulation. Eventually, during temperature swings, this vapor is carried to the outermost layer of the insulation, where it would normally try to escape to the atmosphere. By applying a non-permable layer of paint, the moisture is prevented from escaping. The pressure pushing the vapor out (vapor pressure), which is sometimes quite substantial, has enough force to deform the paint into blisters.

The norwegian method prevents the moisture from ever reaching the siding, as it is carried away by the very slow moving air column and exhausted along with the roof air.

Make sure you nail the bottom of the lap siding. This way, when the siding shrinks and swells, the top of the siding piece will move. Otherwise, if you do the opposite, the bottom will move and it will become uneven. Also, the top is very thin and will crack. It also lets the bottom flap in the breeze, which is not good. The issue of the nail being exposed is minor.

I came up with a new design for soffit vent which I will post drawings and photos here soon. I don't ever plan to make any money from this design, so I will give it away for free. Keep checking back.

The following link has now been fixed

University of Alaska Fairbanksan article describing this technique.

If you found this article useful, please email me. Thanks!

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