It was time to tear down the firewall/support wall for the two chimneys in the house. Instead of the support wall, a 115x180mm glulam beam will be mounted flush with the chimney. (Maybe I will instead choose an equivalent HEB beam to get a few cm larger door opening in width and height).
My question is if the load-bearing beam needs to be tensioned against the outer wall to provide sufficient support for the chimney? The frame of the outer wall consists of 75x230mm raw timber while the force against these is distributed over at least 3-4 pcs.
Thanks for the responses everyone. I can't see any direct cause for horizontal load when examining the frame of the house, but the prestressing was to stabilize the chimneys because the mortar between the bricks had started to deteriorate. It has rained into the chimneys combined with the house being without heating for a long time.
Even though I prefer to stick to wood as a building material, the decision falls on HE200B steel beams (oversized). 12m for about 10k which should be enough for three transitions. No pre-bending of these is needed as they should handle the long-term load according to the designer. I also decide to avoid the prestressing that was the reason for this post in the forum since the load is already high on the outer wall, which otherwise risks failing and transmitting the force to the upper floor in an undesirable way. What's left is choosing the appropriate type of beam for the vertical columns (two supports for each opening), and designing feet that distribute the force on the support in the best way.
There are quite nasty point loads on the joist below. Also, consider the connection at the nodes a bit - I usually weld a bracket that can properly handle moments - then you can account for this in the dimensioning. A fixed encased beam can be made slightly slimmer than a freely supported one. I think there's an old thread here showing how I did it once. The downside to the brackets on top is that they take up some construction height, but it can often be hidden with the ceiling.
The images in your thread about the demolition of the heart wall clearly showed which console you mean. The question is how much should the katet dimensions be extended in this case!? Also considering reverse consoles when installing the pillars for the floor above, against the transfer beam for the ground floor.
The reason is that the chimney itself has taken a lot of damage from previous renovations where it looks like the bricks in the chimney were used as leverage with crowbars and the like. The bricks are completely loose in several places in sections of 3, which initially made me unsure of how the chimney would behave when I demolish the fire wall.
The question is whether the chimney sweep is qualified to say anything about the structural integrity of the chimney. I probably wouldn't consult a chimney sweep until it's time to approve the chimney for use.
Sure, you can go ahead and create a completely relieving construction and cast a foundation under the basement floor to absorb all the stress, but this becomes quite costly as it would require two such constructions.
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