Log Cabin Contraction

At certain times of the year I will get the odd complaint about our Log Cabins from buildings that have been installed in the Autumn and Winter, Early Spring. The height of the complaints will come in around July and August.

Some customers will be nice and ask for advise, others will launch into a big complaint and are not very pleasant to deal with on occasions.

I then have to gently walk through the problem with them until it can be resolved and 100% of the time it is the customer’s own making.

The pleasant guy asking for advice will locate the problem and it’s solved.

The unpleasant guy will demand we go on site and then find the problem for them and all of the time it’s when they paid a ‘Qualified Carpenter’ or a ‘Qualified Joiner’ to install the building as it cannot be their fault.  Unpleasant guy then gets very upset when we charge for our attendance.

To solve this I thought I would write a quick post about this seasonal complaint and here’s a few examples:

Logs have shrunk in the heat.

Logs are coming apart.

Gaps appearing

Gaps appearing in the log cabin walls

Gaps and twists starting in the wall logs

Gaps and twists starting in the wall logs, this one is showing at the top of the wall

Gaps starting to show in a wall of a log cabin

Gaps starting to show in a wall of a log cabin, these gaps are spaced all the way up the wall.

Log Cabin shrinking

Log Cabin shrinking with gaps to the side of the door.

Gaps starting to appear

Gaps starting to appear

Contraction of Log Cabins

This quick piece is talking about the problems we have with contraction. No doubt, about six months from now, I will write one with the opposite problems, that of expansion, both are a powerful force in timber.

Throughout the articles in this blog I talk about expansion and contraction a lot and it cannot be overstressed the importance and the power of this. If you are going to own a log cabin you’ve got to believe me.

Here are some previous articles where I talk about this feature of timber in depth:

My online Log Cabin Advice Manual also talks about this.

Log Cabin Logs

A log cabin log is obviously made from the length of a tree and we try to pick the best bit close to the heart. It not going to grow or shrink much in its length but it can change quite a bit in its height when part of an install.

I’ve had a customer tell me ‘I realise wood moves but this is excessive’ It is not excessive, it is what wood does and it cannot be controlled or helped.

In the moisture content article above I reference some figures that will show a cabin has a potential to move a LOT!

Here’s a good example of a log cabin in contraction, followed by an expansion example. In either case you will see the untreated wood start to show. This is why I advise in other posts to remove the fascia and paint behind them so you do not see this happen either in contraction or expansion:

Contraction example:

Contraction exampe

Contraction example

Another contraction example

Another contraction example with untreated wood showing

Here’s the opposite, an expansion example, notice the original paint lines

Expansion example, notice the original paint line

Expansion example, notice the original paint line

Another example of contraction, please make sure you paint behind door and window fascia to avoid this.

Another example of contraction, please make sure you paint behind door and window fascia to avoid this.

Installation Problem

Of course none of this is helped if the installer is not aware of this or understands this and please believe me, anyone with ‘Qualified’ followed by ‘carpenter’, ‘joiner’ or ‘builder’ will make the same mistake as someone who has never built one before. The difference being of course your average customer will read the information before installing.

So why are we seeing these gaps and why am I having a complaint against our lovely log cabins?

Quite simply, the installer is trying to interfere with the movement of the logs and is restricting them moving. This will be things like:

  • Adding extra timber into gaps meant for expansion
  • Fixing door and window fascia to the logs
  • Fixing door and window frames to the logs
  • Installing shelves, electrics, brackets, 
  • Lifting door and windows up to fill expansion gaps
  • Fixing the logs in many other ways
  • Fascia in corner buildings above the door allowing the cabin to sit on the door frame

Here are some examples of the cause of all the above with pictures:

Fixed Fascias

This door fascia has been screwed to the logs. There was quite a few of these in the install

This door fascia has been screwed to the logs. There was quite a few of these in the install

Gaps appearing

Gaps appearing in a corner building. This is where the fascia above the door has been fixed and no allowance made for contraction allowing the door frame to slide behind it.

Fascia being fixed to the logs restricting their movement

Fascia being fixed to the logs restricting their movement

Door fixed to the wall logs

Door fixed to the wall logs – luckily I caught this one as the picture was for a door query but you can see nails through to the logs and this is a potential complaint in either expansion or contraction. Thankfully the customer removed these before any problems was caused in about 6 months time.

Timber infills

During the winter the wood is likely to be at its biggest and sometimes customers will worry about a large gap they find above a door frame or a window frame. Without realising what it is for ‘Qualified’ …. carpenters, joiners, builders … will be tempted to fill the gaps;

Timber used to fill the expansion gaps.

Timber used to fill the expansion gaps. In this example you can see there is a timber block above and to the side of the window frame. So with this Winter lead solution we come to summer and gaps are appearing all over the cabin and I get the complaint!

Extra timber placed above the door frame

Extra timber placed above the door frame. This wood block has removed all expansion and the whole log cabin will now be sitting directly on to the door frame.

Timber insert placed in the expansion gap

Timber insert placed in the expansion gap and also as an extra problem the fascia is also nailed into the logs.

DIY storm Kits, Brackets, Shelves, Curtains etc

I Haven’t really got pictures of these sort of things that I can show you as it may identify the customer’s cabin but this was an unusual one:

Strapping to act as a storm kit and bracing

Strapping and bracing. The customer had some sort of shelving system attached the sides of the cabin and I remember he was also concerned about bracing for storms as he was very exposed in the highlands. The ingenuity was very good but this was holding the cabin very rigid and when the summer got here gaps started appearing.

If you want to install shelves, black boards, bars, brackets etc you can do so really easily but please consider the expansion and contraction. The articles referenced earlier explains how to do this so you do not have any problems in the long run.

Electricity in Log Cabins

I wrote an article about Electrical installation in Log cabins ages ago and although I have let my personal accreditation lapse it still hold true and we reference this quite liberally, electricians must be made aware of the expansion in log cabins.

Here’s how to do it:

Flexible expansion to allow for the cabin to move.

Flexible expansion to allow for the cabin to move.

This is what can happen if you do not tell your electrician that a log cabin is made of wood and expands and contracts:

Log cabin has contracted and no allowance has been made for the trunking. This is a potentially dangerous situation as all the wire and terminations will be under strain.

Log cabin has contracted and no allowance has been made for the trunking. This is a potentially dangerous situation as all the wire and terminations will be under strain.

Consumer unit is fixed across two logs, this will cause problems in both contraction and expansion and may cause numerous problems least of all it compromising the installation itself.

Consumer unit is fixed across two logs, this will cause problems in both contraction and expansion and may cause numerous problems least of all compromising the electrical installation itself.

Summary of contraction in a Log Cabin

Log cabins move, whether it’s one of ours, someone else’s, regardless of thickness, all wood moves, it can’t be helped. It’s full of straws and these straws will suck in and expel moisture:

Layer upon layer of straws all drawing water for the tree. Many now support the Cohesion method theory where a tree draws its water using the tension of water.

Layer upon layer of straws all drawing water for the tree. These straws stay open and need to be treated to block them up.

You can see from the structure of the wood that these straws need to be blocked up, amongst other things this is the purpose of a good quality treatment and sufficient coats, these articles explain more:

I’ve said it several times, please don’t use anything cheap on any log cabin, we’re trying to inhibit the movement. A cheap treatment will not do this and you will have quite a bit of movement over the first year.

We do find though that after a year and the full season cycle we will never hear from a log cabin customer again. If you are going to have a problem with expansion or contraction it will be within the first six months of ownership as you will have either treated it well or the straws will start to collapse and die more.

If you have a log cabin that is showing these signs, before you complain to us or the person you bought it from whether it is our product or not please check the following:

Check for:

  • Fascia screwed / nailed to the logs
  • Any restriction to the logs at all
  • Shelves, curtains, brackets, fixings on the wall
  • Expansion Gaps above and to the side.
  • Finishes above Corner building doors.

This is all applicable to any log cabin, I hope it helps if you are seeing these problems whether you bought from us or another manufacturers building.