HUGE joist notch

[electrogear]

Hi,

I bought a house to renovate and noticed that the toilet has been moved from the outside wall to an internal wall. I pulled up the bathroom floor to find that the toilet waste had been re-routed through 2 joists! 125mm has been removed from the 150mm joists, leaving just an inch!!! The notch is very close to the wall it sits on (about 30cm away) and there is a blockwork wall sat on top of this joist, perhaps 70cm from the supporting wall (the upstairs walls are blockwork built on timber, which was common practice in the 1960s).

There's noticeable deflection in the joists as you would expect, and you can in fact see a 5mm gap between the joist and the blockwork wall sitting on top of it. It's only the fact that the blockwork is tied into the outside cavity wall that the whole wall hasn't dropped.

What would be the best course of action to fix this monstrosity? Obviously I've already removed the waste pipe and rerouted it back along the external wall, but how can I repair the joist? My (amateur) thought is to acro the joist until it's level again and then use some sort of steel plate/strapping (or maybe a 1m section of joist) to give the butchered joist some strength back. I'm hoping I can do this without having to replace the whole joist, which would be a b&t^h of a job.

Any advice would be very welcome.

 

[Mr Chibs]

Without seeing pics a bit difficult, but perhaps you could just bolt on a new section of matching size joist to the side of it, then some noggins at 90° of the joist to neighbouring joists, to take some bounce out.

Use something meaty like M10 coach bolts/screws, not sure I'd worry about props etc, if it's been like this for years, it's surviving, and you will only be making it better.

 

[bernardgreen]

You will need to fill the notch with solid hard material as well as a plate or similar along the sides of the joists,

As mentioned sistering the joist ( timber bolted to the sides ) is an option. The bolts must be fitted midway between the top and bottom of the joists.

The bottom half of a joist is under tension and the top half is under compression as the joist tries to bend under load. A notch in the top side will close as the joist bends. The mid point ( from top to bottom ) is neither under compression or tension hnec holes for bolts there will not weaken the joist.