Anybody that is in the process of designing and building a new house runs into this discussion: should we build with a damp-open construction, with damp-open walls and roof, or not? Because opinions differ, and the debate is heated, amoung architects and building engineers. One is more energy-efficient, but the other is more ecological… etcetera…
We build our wooden houses mostly from laminated wood. Laminated wood is wood that has been cut into long boards, then glued again to form one massive log. It may sound a little strange to first cut wood into pieces and then glue it back again, but this cutting and glueing has distinct advantages.
massive wood by the roadside
Wood dries over time. Immediately after cutting wood has a moisture content of 50%, and within a few months by the roadside the moisture content has already dropped to 30%. But before we can use the wood in house construction, the moisture content should be lower than 20%. And when the house is finished, over time the moisture content will drop to somewhere between 5% and 15%, depending on ambient temperatures and relative humidity of the surrounding air.
cracked wooden disc
And with the drying comes the cracking. A little crack here and there may not be a problem, but big cracks are not good for the insulation properties.
And there is little you can do about it. Except laminate: laminating results in wood with minimal to no cracks. More info here. So that is reason no. 1 why we use laminated wood.
Standard massive wood can have a moisture content from 20% to 30% at assembly time, and the drying not only makes the wood crack, it also makes the wood shrink. And shrinking can give you a few headaches.
Here we go: the height of your house goes down from say 6.00 meters to 5,50 meters. Yes, massive non-dried wood can shrink that much! No problem, you say? So what about the doors and windows? They don’t shrink, so how will they still fit in the walls? And what about the raingutter downpour pipes? They get pushed into the ground, or they rip of the roof. Vertical copper pipes inside your house for hot or cold water, what do you think will happen where they connect to the sink or the crane?
glulam beams for roof
Laminated wood is much drier (below 18% moisture content) when we use it to assemble our houses. It still shrinks about 1% in size, but we can easily deal with 1%, we have standard solution for that.
Stronger, Longer Spans
Massive beams come in standard dimensions, with a maximum length of about 6 meters and diameters of up to 30 centimeters. You need something longer, or thicker? Well ehh… sure you can buy it, but it will cost a fortune. I car terms: more like an Aston Martin or a Bentley. But our houses are more like Volvo.
Laminated wood you can produce in any length or diameter. And that is what we do. Thanks to laminated wood, we can have overlay ceilings that span 12 meters instead of 6 meters, without a column in the middle. And that is: 12 meters in Norway, with a substantial snowload. Serious stuff.
bridge from laminated wood in Sneek, Netherlands
Actually we could go further. With laminated wood you can easily build bridges that carry 30 tonne trucks. But we still need to transport our logs, so 13 meters is about the maximum length that we use or they will not fit in a truck.
How To Laminate
So how do we laminate? We could try to explain, but it is far easier to take a look at this Youtube movie.
We build houses from wood. From wood you can build gardening equipment, cupboards, airplanes, kitchen utensils, children’s toys, bicycles and wheels. Wood is really a nice material to work with. But skyscrapers? Is wood suitable to build a skyscraper?
Architect Michael Green says yes, he wants to build sky scrapers from wood. You may think Michael is a dreamer, but actually in the city of Amsterdam Dutch architect Tom Frantzen built a six floor thirty meters high wooden building. Not exactly a skyscraper, but not your average two storey house either. To be honest it is not entirely wood: there is a concrete elevator shaft and some floors are partly steel and concrete, but the load bearing construction is all wood.
Michael Green wants to go higher: thirty floors, he says…
This post is about wooden houses from Russia. Traditional wooden houses from Russia are a little different from the houses that we build, both from a design point of view as well as technically.
wooden house in Russia. Photo by Maxim Shemetov.
The design and style of the traditional Russian wooden houses obviously is different from what we are used to in West Europe. Generally speaking the materials are a little rougher, while at the same time there is a lot of fine hand-crafted woodwork in the details.
Technically these houses often have little in the way of a foundation. Many are built on permafrost terrain where it is difficult to dig a hole and build a foundation, so the house is built on top of the permafrost. Then once the house is built, the heating makes the permafrost a little less perma, and the house starts moving.
Many of them are built using round logs for which you will have a problem getting a building permit here, unless you are high-up in the Alps and also they use non-dried non-laminated wood. Non-dried non-laminated wood shrinks and cracks, but otherwise it is not that bad, and it certainly has a lot of charm. It’s a matter of preference.
There is no additional insulation on the outside or the inside. Even with the excellent insulation properties of wood (compared to brick or concrete), these houses will never meet today’s West European insulation requirements. Walls have Rc-values around 1.5, no higher than 2, compared to our walls having anything between 6 and 10, and these houses are not airtight: there will be drought in every corner and around every door and window.
With the low cost of energy in the outback (plenty wood) such Rc-values are not really an issue. Mind you, until recently these Rc-values were quite the norm in Europe as well. Also a little drought works like ventilation which is always good against condensation.
The photo on top was taken by Maxim Shemetov, a Russian photographer from Moscow. Maxim’s work with more images of traditional Russian wooden houses can be found here:
Previously we wrote about types of wood (wet, dried, laminated) and the shrinking of log houses and how we deal with the shrinking. In this post we want to show a little more about the actual drying process, and cracks. Because drying and cracks are very much related.
Why Does Wood Crack?
The photo below shows a crack in a wooden disc. Why does wood crack like this? Very simple: drying.
cracked wooden disc
When wood dries, the drying process starts at the outside of the logs. While the humidity goes down from 15% to 12% near the outside of the log, more to the the center of the log the humidity initially remains at 15%. And that is a problem.
Previously we wrote about a house that we built in Belgium. This house had double outside log walls (2 x 8 centimeter massive wood) with 20 centimeters cellullose between the walls.
The advantage of this construction was the damp-open construction (no plastic foils anywhere in the walls) plus the enormous thermal capacity of the walls. In the evening the walls warm the house, during summer daytime they cool the house.
And there is yet another advantage of cellulose: the fire rating. If impregnated with fire retardant material, cellulose will not burn. Look at the video below where different insulation materials are compared. It is not a scientific test, but it gives a good impression of what happens in case of fire.
We try to avoid polyethylenes and polystyrenes, whether extruded or expanded, as much as we can. It has zero thermal mass, it burns and often with a lot of black smoke, it turns into chemical waste.
Instead we use Rockwool, cellulose, sometimes wood fibre (not tested in the video above). But the poly-stuff we avoid.
Long ago the quality of a wooden house depended on the location of the factory. A factory in the north used wood from the north, which was growing more slowly and was denser and heavier.
But times have changed. First of all there is a very active European wood market, and just like oil, wood is a raw material that is being actively traded all over the world. Also modern wood treatment techniques have improved the quality of wood as a building material in such a way that nowadays more factors come into play. It is not just northern wood that is a good building material. Continue reading →
If you are planning to build a wooden house, most likely you would like to know possible options for exterior finishing. Different types of wood, boards profile and the right choice may have a big difference on a final house look and durability. We use spruce or larch wood for the exterior finishing. What are the main difference and which is better?
A wooden house will shrink. No matter how dry the wood was initially, over time, during a period of approximately two years, all residual humidity will slowly evaporate from the wood and the wood will become more dry. Wood shrinks in one direction only: lateral, but not longitudinal, or in other words, logs will become thinner, but not shorter.