In our first article on settlement we calculated each standard log settles by 4mm from 180mm to 176mm aprox and the laminated log settles by 3mm from 180mm to 177mm. This means the standard log shrinks vertically at a rate of 22mm/ metre and laminated at 16mm/ metre. Settlement stops after about 2 years.

Let’s make some observations based on standard log shrinkage. The min standard for ceiling height is 2.4 metre so your ceiling will lower 52mm (2 inches). For example if you tile your bathroom from floor to ceiling the pressure of the logs will break all the top row of tiles. If you construct a stud (timber frame) wall from floor to ceiling the consequences will be worse. Because the stud wall can take the weight of the logs, the log wall will open up and you will have gaps to the sum of 52mm. This is very serious and will leave an exterior wall open to draughts and weather.

If we take it that counter tops, sinks and toilet cisterns are aprox 900mm from the floor we can expect 20mm (3/4 inch) log settlement. Even the pipe work to these units has to be accommodated so it is important to have proper consultation with electrical and plumbing contractors. Even a 600mm (2 foot) high mirror fixed top and bottom to a log wall will have to make way for 13mm of settlement. The mirror will crack.

Most Canadian and some Scandinavian manufacturers have timber frame gables and upper floors. So the upper floor will not be affected by settlement. But anything that spans the two floors will be affected by the settlement of the ground floor logs. So where the upper floor and the roof meet the chimney stack the floor and the rafters will drop 52mm.

Where you have log gables and log upper walls the rafters will drop 104mm. My own house is 6 metres from dpc to ridge and so the roof dropped 132mm (5 inches) around the chimney. If you fix your rafters to the chimney you have a very serious problem. Where does that 132mm go? The roof will belly up by this amount and cause other problems.

The chimney stack must be free standing inside the log house and The Log House Company have designed a special flashing unit for roof to chimney detail.

We calculated and accommodated this settlement from the beginning and because we now have a number of houses constructed over 8 years we are not just guessing. We have worked very successfully as consultants on supply only and self build projects.

So how do we accommodate all this settlement? Apart from the chimney flashing unit designed by The Log House Company some manufacturers supply grooved and sliding brackets for rafters to wallplate and for stud to log walls. Stud walls must be min. 52mm lower than the ceiling and a cover board installed to cover the gap. In some areas the grooved brackets won’t work. For example, for kitchen units we groove 50×25mm timber with a jig saw and screw through the groove onto the log wall. Then we screw the units to the grooved battens. For tiling we use the same method using 100×25 battens, then screw plasterboard to the battens and tile. This is good because it leaves a 25mm air gap. Electrical conduits must be grooved also and piping loose clipped. Calculate and use your head.

Please Note: The Log House Company takes no responsibility for use of the above information. They are general guidelines and suggestions. Each project should be individually assessed.

Regards
Eamon Murray

Filed under: Log House construction in Ireland on February 3rd, 2008