Posted this question under Groundwork, which might not have been quite right... I'll try here instead.
I've removed the ceiling in the basement, and some floor joists are quite rotten at the ends. The house is from the 1800s, and there's been a lot of old junk to replace. The inner floor, as shown in the picture, is in great condition, so I want to preserve it...
How do I solve this? The span is 2.5m, and my initial thought is to place new studs next to the beams and then cut away the rot as best as possible. The beams stick into the foundation wall and out to the crawl space foundation where the timber stands, maybe 40-50cm into the basement wall.
However, I see two problems... The inner floor is nailed to these joists. If I manage to remove them completely, the floor won't be attached to anything anymore... it might be difficult to fix from underneath???
As mentioned, the foundation wall is 40-50cm thick, and it's cast around the logs... I guess I'll have to chisel next to the log, but I'm afraid it won't be possible to get as much of the new floor joist in as 40cm...
It can also be mentioned that I replaced three floorboards that were over the foundation wall, closest to the outer wall. The reason for this was that they were cracked and a bit worm-eaten. However, I didn't see any signs of bad joists from above... strange...
Your floorboards are probably nailed into the groove down into the floor joists, which will make it difficult to remove the joists without damaging the floor.
But how bad are the joists, how far can you insert a knife? I would probably opt to tear down the subfloor boards and reinforce the joists by cutting away to fresh wood and then adding new timber on the sides. Possibly hanging up a bearing line on the edges for the new regulations if the joists are seriously decayed at the foundation wall.
I haven't started cutting into them yet, but I guess that as usual in this house, it's not as bad as it looks, only rotten a couple of cm in. How do I set a support beam on the edge then? One thought I have is to place a steel beam of 3 meters or whatever it ends up being and build up two or three leca "pillars" as support, but it feels a bit like overkill. Additionally, it would look very "repaired." Bolting a joist to the basement wall also feels a bit questionable in terms of durability... no real sense of how well it holds to bolt something into a concrete/stone wall.
Couldn't one drill up the wall next to the beam and insert a joist there??
Not an expert on bolting into concrete. But it should probably hold really well with expansion bolts or something similar. In the pictures, it almost looks like there's a ready-made small support on the wall that you could use?
Chiseling out new holes for beams is probably possible but likely a heck of a job. What is the wall made of? If you encounter granite, that won't be much fun.
Do you have more loads from above on the beams than just the floor?
I don't quite understand how it is structured, but do you even have to remove these bad beams? Wouldn't it be enough to attach joist hangers (or something else new beams can rest on, such as a supporting beam) to the foundation wall with solid screws and then place more floor joists parallel to the existing ones? 2.5m is not a very large span.
Well, you might be right. It's structured such that there are floor joists cc70-80cm from wall to wall with a span of about 2.5 meters and the floor is perpendicular and nailed to these joists. The inner wall that divides the basement in half has a solid "shelf" where you can insert a new beam, but the outer wall is built up to 4-5cm from the inner floor....
I'm a bit unsure about how I need to attach the new joists. Joist hangers into an unknown basement wall might work fine. Moreover, it feels a bit strange to just set new ones without fastening the floor to them in some way. Or can you glue pieces against the inner floor that you screw into the new beam? The reason for gluing "pieces" is that a new straight floor beam surely will not lie flush against every floorboard.
If you press up the new beams against the ceiling in the basement with a jack during installation, that should be enough, I think, as the floor is already attached to the old beams. The important thing with the floor is that it doesn't collapse, and that is achieved with new beams.
A support beam with a 20 cm concrete screw or similar should work well. If you attach a regular floor joist to, for example, glulam, you use joist hangers and small anchor screws just over 4 cm. Here you also have the old beams plus new ones.
Knock off the brick next to the beam, chop away the thorns and insert a 145 rule which was the max that could be fit in
It went smoothly with this one as everything rotten could be removed since the log was spliced 5cm into the wall with a "new" beam, the remaining 3 won't be as easy to fix....
