Lithouse build houses with three types of walls:
- panel walls
- log walls
- cross laminated timber walls
They all have pro’s and con’s, let’s dive into the details.
Panel walls are essentially hollow boxes filled with insulation material. You build a frame from 195 x 60 mm beams, and front and back you close with an 18 mm OSB-plate. Now you have a hollow box, say 2 x 3 meters and 231 mm thick. Fill the box with mineral wool insulation and presto: you have a wall, or at least the most important part of the wall.
This type of wall has some advantages. These walls are light, and can be produced quickly. Also you can produce them in a factory under optimal conditions and all you have to do is put them on a truck and hoist them onto the foundation.
In France this kind of construction is called ossature bois, ossature meaning frame. In The Netherlands it is called houtskelet with skelet translating to skeleton.
A log wall is more traditional. A log wall starts with logs: massive wooden beams 120 mm thick x 180 mm high. The beams are stacked into walls, and then insulation is added on the outside. It is a very traditional way of constructing houses and we like it a lot. There are some disadvantage though. For one, the logs shrink slightly after assembly so your house will settle and all heights will come down by 1% approximately. 1% May sound like not much, but you have to take special precautions to make sure your doors and windows still fit after a year. Also your interior will be all wood so keep that in mind.
Cross laminated timber walls
Cross laminated timber or CLT for short is a relatively new technique. You take small wooden planks, say 40 x 40 x 3000 mm and glue them together to a wooden plate, 40 x 3000 x 3000 mm. Then you take a second plate and glue it on top of the first, now you have a 80 x 3000 x 3000 mm plate. And then another, now we are at 120 x 3000 x 3000 mm. These are sure massive plates weighing 500 kilos a piece and forget about man-handling them on the building site, you will need a crane.
Cross laminated timber is a bit like a log wall. We add insulation on the outside. Cross laminated timber does not shrink and the dimensioning is very accurate. Again your interior will be all wood, but this time it is not logs that you will see but instead it is more modern and industrial, a massive wooden plate without any grooves. Combines very well with stainless steel and fine polished concrete floors.
Architects love panel houses because of the extreme flexibility. If you can draw it on a CAD-station, you can build it. Which is not the case with a log house. With a log house there are all kinds of special design limits and conditions that you need to take into account. One example: you can finish inside walls any way you like. Gypsum, OSB with or without wall paper or painted, cherish veneer, possibilities are endless. We have one client who will finish his partition walls with metal sheets. Not so with a log house: you will see logs and that’s it. Another example: you will always need two or three logs above a window, so windows all the way to the ceiling (architects love windows to the ceiling) is a nono. There are solutions to overcome this special problem, but still: a panel house is easier to design. Final example: a panel house you can very easily add stucco on the outside. With a log house it is possible, but you need to take some precautions or your stucco will fall on the floor after two years.
Cross laminated timber houses share flexibility with panel houses, but at a price: they are much more expensive, see next section.
Another flexibility issue concerns the interior or partition walls. In a panel house, after thirty year, you can remove some inside walls and place them somewhere else, move them around. Of course you must take care of the load bearing walls and make sure the house does not collapse, but in general there is some flexibility. Not so with a log house: you can cut an extra opening in some walls, but completely removing walls and build new ones somewhere else is almost impossible. Your floorplan is more or less fixed in a log house.
As far as cost is concerned, there is not much difference between panel walls and log walls. Panel walls are slightly less expensive, but when we are done building the structure, you still have to finish the inside walls with stucco. Not cheap, and bottom-line you will not save a lot of money.
Cross laminated timber is quite a bit more expensive at the moment. It is new technology and cost may come down, but at the moment you should expect 10-20% extra cost for a CLT-house compared to a log house.