RULE #1 – Respect the shrinkage!
When building with green timber movement is inevitable. With the correct log building methods in place this will never cause any issues, however if the initial shrinkage and seasonal movement of the building is not taken into account many problems can arise…in the case of doors and windows it may mean that one morning you wake up and can’t get out of your house!
Around doors and windows our tried and tested method is to cut a vertical slot with a chainsaw and set in a piece of 4×2 down the log ends either side of the opening, as shown in the picture above. We then fix the door frame into the door lining, place the unit in the opening and fix through the frame ONLY into the 4×2. Expanding foam is used behind the 4×2 to create a seal.
Because the 4×2 is fixed to the frame and clamped by the logs the logs are free to slide around the frame without causing disruption to the swinging of the door or window.A ‘shrinkage gap’ is also left (75-100mm over the height of a doorway) to allow the logs above the opening to move down towards the frame. This gap is filled either with expanding foam or tightly cut soft foam to create a seal.
Other areas to watch for shrinkage are staircases and vertical posts. We get around this by using Screw Jacks. These are heavy duty threaded bar, welded to a footplate with a moveable steel plate held up by a nut. When the cabin walls shrink, simply adjust the nut to allow the fixed element of the building (stairs or upright post) to follow the shrinkage.
Another cheeky trick – When a stud wall meets a log wall, cut a slot for your wall finish (plasterboard in the example pic) to slide into. This is better than scribing a cover strip to the form of the logs because if you do that you have to re-scribe the cover strip successively as the wall shrinks.
It is important to remember that when owning a log home you should keep an eye on the shrinkage and occasionally adjust fitments as required. Adjustments are mainly needed in the first 18 months of the cabin being constructed as the moisture levels in the timber reach an equilibrium with the atmospheric moisture level. We always offer to go back to a project to make these adjustments in the initial drying out period and explain what to watch out for before we leave.
Log building is a tricky business, good job you came to the experts.