I am considering replacing the windows with larger ones around the ground floor in a log house that originally had 1 floor with an attic but the roof was raised 25 years ago.
So today, it's 2 floors with an attic.
Today, there is 1.5 log above the windows, then above that is the new construction with the sill lying on the top log and standing studs (modern construction).
To fit larger windows, I need to cut away half the log as well as 5cm at the bottom of the last full log.
This applies to two windows on each side of the house, and 120cm each.
The question is how serious this might be?
The house is additionally insulated and I have the possibility to place a beam type 44x210 on the plate against the log above the window and about 15cm out on each side of the opening.
Comments?
So today, it's 2 floors with an attic.
Today, there is 1.5 log above the windows, then above that is the new construction with the sill lying on the top log and standing studs (modern construction).
To fit larger windows, I need to cut away half the log as well as 5cm at the bottom of the last full log.
This applies to two windows on each side of the house, and 120cm each.
The question is how serious this might be?
The house is additionally insulated and I have the possibility to place a beam type 44x210 on the plate against the log above the window and about 15cm out on each side of the opening.
Comments?
It primarily depends on what you have resting on the logs above the opening. Is there a beam supported there or what? Maybe nothing?
It secondly depends on how the half lower log is anchored to the upper whole one. If they are just loosely resting on each other, the risk is smaller from a deflection point of view that something will collapse if you remove the half.
Whether you can gnaw five centimeters from the lower part of the whole log is another question. It is significantly more sensitive to reduce the height from the bottom edge of a load-bearing log if something rests on it because the neutral axis (the boundary between tensile and compressive stresses in the cross-section) moves up and reduces the bending resistance of the log, which relates to its strength.
Thirdly, it depends on how it looks above the whole log. Are there more whole logs? In that case, you can use flat iron to 'hang up' the gnawed whole log to the upper ones and transfer the load from the gnawed one to the untouched logs higher up.
A little guidance perhaps?
_____________________
Builder
It secondly depends on how the half lower log is anchored to the upper whole one. If they are just loosely resting on each other, the risk is smaller from a deflection point of view that something will collapse if you remove the half.
Whether you can gnaw five centimeters from the lower part of the whole log is another question. It is significantly more sensitive to reduce the height from the bottom edge of a load-bearing log if something rests on it because the neutral axis (the boundary between tensile and compressive stresses in the cross-section) moves up and reduces the bending resistance of the log, which relates to its strength.
Thirdly, it depends on how it looks above the whole log. Are there more whole logs? In that case, you can use flat iron to 'hang up' the gnawed whole log to the upper ones and transfer the load from the gnawed one to the untouched logs higher up.
A little guidance perhaps?
_____________________
Builder
Thanks for the input.
Above the entire beam, there is a sill of about 1x5", and on that, vertical studs 1200c/c. Modern construction with plasterboard and so on. There are no more beams above that need to be cut out.
How the beams are anchored I can't see without tearing down the interior walls or outer panel including insulation.
If we assume that "nothing more" than the pressure from the traditional framework in the upper floor and roof, etc., is evenly distributed over the 125cm we're talking about, then the pressure shouldn't be a problem.
Lateral tensile forces even less so, right?
There will be 150mm (in height) left of the last beam, and I will, in any case, bolt a 45x155 to the beam as extra reinforcement.
Am I on thin ice anyway?
Above the entire beam, there is a sill of about 1x5", and on that, vertical studs 1200c/c. Modern construction with plasterboard and so on. There are no more beams above that need to be cut out.
How the beams are anchored I can't see without tearing down the interior walls or outer panel including insulation.
If we assume that "nothing more" than the pressure from the traditional framework in the upper floor and roof, etc., is evenly distributed over the 125cm we're talking about, then the pressure shouldn't be a problem.
Lateral tensile forces even less so, right?
There will be 150mm (in height) left of the last beam, and I will, in any case, bolt a 45x155 to the beam as extra reinforcement.
Am I on thin ice anyway?
No worries. You seem to have a pretty good grasp of what's going on.
However, a 'syll' of 1"x5" doesn't sound great to me. It seems more like a nail board to get a flat surface to place the wall rules on. It doesn't carry anything, in other words.
If nothing else rests on that 'syll', I suggest you hollow out 45 mm deep and 120-145 in height in the wall rules and fit in a 45x120 or 45x145 on edge over the opening.
Bolting a horizontal 45 thick plank to the upper beam is a fairly pointless measure since they will not interact very well with each other in terms of shear. You would then need to plane the top of the beam flat and glue with a polyurethane adhesive in the joint and bolt twice as tightly at the supports as in the center if any improvement is to be made. (Place two strips of thick cardboard on top of each other and pinch them with your thumb and index finger on both hands at each end, then ask someone else to press down on the flat with a finger in the middle, and you will feel the ends creeping between your fingers. The explanation is that the lower strip is subjected to tensile forces and the upper to compressive forces, and since both strips are equally long, the upper should become shorter and the lower longer if the ends are to remain equal, which they obviously won't.) Therefore, hollowing out for a 45x120 (or 45x145) on edge is a better reinforcement measure.
_________________
Builder
However, a 'syll' of 1"x5" doesn't sound great to me. It seems more like a nail board to get a flat surface to place the wall rules on. It doesn't carry anything, in other words.
If nothing else rests on that 'syll', I suggest you hollow out 45 mm deep and 120-145 in height in the wall rules and fit in a 45x120 or 45x145 on edge over the opening.
Bolting a horizontal 45 thick plank to the upper beam is a fairly pointless measure since they will not interact very well with each other in terms of shear. You would then need to plane the top of the beam flat and glue with a polyurethane adhesive in the joint and bolt twice as tightly at the supports as in the center if any improvement is to be made. (Place two strips of thick cardboard on top of each other and pinch them with your thumb and index finger on both hands at each end, then ask someone else to press down on the flat with a finger in the middle, and you will feel the ends creeping between your fingers. The explanation is that the lower strip is subjected to tensile forces and the upper to compressive forces, and since both strips are equally long, the upper should become shorter and the lower longer if the ends are to remain equal, which they obviously won't.) Therefore, hollowing out for a 45x120 (or 45x145) on edge is a better reinforcement measure.
_________________
Builder