Floor Joist end repair - in situ

[Samuel17]

Hi

This is a topic that has come up before on the forum, however seeking advice specifically around options for in situ repair. The house is Victorian terrace, around the late 1800/1900 build with a cellar located under half of the house footprint (Under the kitchen). The cellar is generally pretty dry, however some of the joists ends to the rear of the property are showing some signs of softness within the wall sockets. From a probe inspection of the rest of the joist spans they appear solid, with little indentation when pressed with a screwdriver, even in close proximity to the wall. Based on this it makes me think that a full joist replacement isn't the best way to go. Given the kitchen is above, there would be significant disruption if full length joists were to be replaced, the cellar is approx 3.5m x 4m and the joists span across to a wall in the middle of the cellar. Access is down a staircase so its limited in the length of materials you can get down there.

Ive had a look around and spoken to a few structural engineers, who seems to think in situ repair could well be feasible. Current options that might work could be:

1. Use of bower beams, although I'm unclear if this is bad practice if repairing a number of joists - doing this in situ seems feasible and it does seem a fairly common method.
2. Mounting an angle to the rear wall to support the joists ends. The existing ends would be cut back near the wall and treated, angle would be fixed using appropriate resin anchors suitable for stone. Again seems doable in situ just limited on the length you can cut off.
3. Potentially widening the existing pockets and sistering the joists into these.
4. Putting a steel across perpendicular to the joists, cutting the joists back and using hangers to attach the new joists to a timber sitting in the web. Any steel beam would need splicing however as I don't think you would get the full span beam through the coal hatch into the cellar. In addition the beam would need masonry piers to support it at the side of the house which adds to the complexity!

I would welcome the thoughts of the forum as to the suitability of the options , and any other ideas not listed! Currently trying to work out the best way forward, from my assessment the main beams seem to have a fair amount of life left in them, so if I can move away from a complete replacement that would be ideal. The kitchen is in a excellent condition, so would rather not rip it out if I can!

Thanks in advance

Sam.

 

[fernicarry]

I had to look up bower beams. Seems like a good solution to the problem of slotting a new piece into the existing pocket when access is restricted. Longevity would depend on the quality of the coating which tends to be pretty rubbish on most products I encounter so that would put me off. I dare say it will last long enough to become an SEP.

What I did for my first floor joist ends at the front of the house -- support joist (I actually jacked it until it just lifted), cut back by as much as possible, place new piece in pocket and bolt a sister on to both. Ideally you want 2 or 3 feet of overlap on both new and old. You need that sort of space to maneuver the new piece in anyway. Bizarrely a couple of wall pockets were already double width so those ones were easy.

Generally I bolt all the way through with 12mm studs, dogs tooth washers in the middle and washer plates on the outside. In one case where I only had access to one side I did use coach bolts but I wouldn't be happy completely relying on them for all of the connections. Seems to me like they could pull out too easily if there was a twisting force and the wood was a bit soft. Again I dare say the people who make these things know what they are doing.

I did consider anchoring something onto the wall to carry a sistered end but with stone rubble walls getting a fixing would be pretty hit or miss.

Working from below your obstacle will be removing the rotten end without causing too much disturbance above. Floorboards and partition walls will be nailed into the joists from above and those nails will pull through before they pull out. Then you'll need to fix those into the repair section from above. Enlarging the pockets may be more attractive than dealing with that.

Just about to do another one, ground floor this time so no pockets to worry about, just bolt on a sister and pack it onto the sleeper wall.

 

[Cubist]

Hi Sam,
I was about to say that the Bower Beam solution looks the simpler and least expensive route to go but @fernicarry beat me to it. Ho hum, late to the party again.
Cheers,
Cubist