Hello!
We are expanding and extending an existing 1930s house with a mansard roof. The old trusses are made of 120*70 timber with a collar tie located about 70cm from the top. These have no additional reinforcement or support and have survived well for the past 80 years. However, it might be that the longitudinal inner wall, which was only attached with a few 5-inch nails to the break, but was quite substantial and stood on the joists, may have helped support the truss at the break. Therefore, it is difficult to rely on the experience that these trusses have managed without support.
The new trusses will be in 220*45 K24 timber + a 45*45 nailed on top and constructed in the same way. If possible, we would prefer not to have to insert a beam at the ridge or break as support. The old trusses will be built up with 145 mm studs on top of the old ones.
The span between the walls is only 4.70m, and the height to the ridge is about 3.10m. The height to the break is about 1.50m.
I am looking for someone who has experience with similar trusses that have no additional support.
We are expanding and extending an existing 1930s house with a mansard roof. The old trusses are made of 120*70 timber with a collar tie located about 70cm from the top. These have no additional reinforcement or support and have survived well for the past 80 years. However, it might be that the longitudinal inner wall, which was only attached with a few 5-inch nails to the break, but was quite substantial and stood on the joists, may have helped support the truss at the break. Therefore, it is difficult to rely on the experience that these trusses have managed without support.
The new trusses will be in 220*45 K24 timber + a 45*45 nailed on top and constructed in the same way. If possible, we would prefer not to have to insert a beam at the ridge or break as support. The old trusses will be built up with 145 mm studs on top of the old ones.
The span between the walls is only 4.70m, and the height to the ridge is about 3.10m. The height to the break is about 1.50m.
I am looking for someone who has experience with similar trusses that have no additional support.
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Hello,
"the longitudinal inner wall which was indeed only attached with a few 5-inch nails to the fracture" - it sounds like you are talking about the wall that separates the attic space from the living area. It is usually built against the support legs, which are an integral part of the truss itself!
The support legs can be located either directly under the "fracture" or further out, towards the steep part of the upper beam. I would think that the latter is the most common. However, support legs may be missing on one side of some trusses, for example, near stairwells.
Our house from the 1920s has support legs. The extension from 1981 has a mansard roof without support legs but instead has a laminated timber beam at the ridge and both "fractures."
A picture of a truss for a mansard roof without support legs can be found here: http://www.sepa.fi/SV/takstolar/mansardtakstol/mansardkonstruktion.html - but as you can see, it is a more complicated construction.
"the longitudinal inner wall which was indeed only attached with a few 5-inch nails to the fracture" - it sounds like you are talking about the wall that separates the attic space from the living area. It is usually built against the support legs, which are an integral part of the truss itself!
The support legs can be located either directly under the "fracture" or further out, towards the steep part of the upper beam. I would think that the latter is the most common. However, support legs may be missing on one side of some trusses, for example, near stairwells.
Our house from the 1920s has support legs. The extension from 1981 has a mansard roof without support legs but instead has a laminated timber beam at the ridge and both "fractures."
A picture of a truss for a mansard roof without support legs can be found here: http://www.sepa.fi/SV/takstolar/mansardtakstol/mansardkonstruktion.html - but as you can see, it is a more complicated construction.
Yes, that's correct, it's such a wall. However, it wasn't against any support legs as those don't exist as mentioned. Instead, it was a loose plank of 1.5*4 meters that was set up against the inside of the roof panel in the break.
This is what it looks like but without the interior wall, and we hope to build the new trusses like this.
This is what it looks like but without the interior wall, and we hope to build the new trusses like this.
Completing the thread with a response from the constructor for information to those of you in a similar situation as ours.
The trusses are entirely self-supporting, made of 220*45 K24, even without a collar tie. This applies even, to my surprise, to the larger trusses with a 7.5m base internally.
We also received a solution for how to support the four valley gutters and the trusses that rest on the valley gutters. They rest on a 3-part laminated beam that goes between the first whole trusses and rests on a load-bearing interior wall, which in turn stands on the steel beams we have to support the joists. The laminated beam and interior wall are marked in red in the picture.
Furthermore, I can strongly recommend drafting both new construction and extensions/renovations in Google Sketchup. It has taken many hours but saved even more when in contact with the constructor and testing construction solutions.
The trusses are entirely self-supporting, made of 220*45 K24, even without a collar tie. This applies even, to my surprise, to the larger trusses with a 7.5m base internally.
We also received a solution for how to support the four valley gutters and the trusses that rest on the valley gutters. They rest on a 3-part laminated beam that goes between the first whole trusses and rests on a load-bearing interior wall, which in turn stands on the steel beams we have to support the joists. The laminated beam and interior wall are marked in red in the picture.
Furthermore, I can strongly recommend drafting both new construction and extensions/renovations in Google Sketchup. It has taken many hours but saved even more when in contact with the constructor and testing construction solutions.