Rotten joist Close to a wall

[cdtsilva]

Hi Everyone.

 

While going for a very routine selaant replacement job on my newly bought house - I noted movement - and after investigation I realized the bath was sealed with expanding foam just under the damaged sealant resulting in water ingress and extensive damage to the floors underneith. None of this was visible prior. The surveyour quote  high humidity and possible investigation to rising mould on the walls underneith, but further structural analisys would not be possible without taking things apart.

 

Presently I removed the ceilings to the lower floors covering this joist and will later remove the toilet to raise them (as it was fixed to the wall in a lower position and shows signs of leackage in the past too).

 

I will have to break the new joist into two pieces to secure it into the wall cavities at each end, but given it is so close to the wall - I cant get any nails or screws on that side to fix the joining metal plate. I considered drilling into the wall, but its 15cm or rubble till I find solid stone and often the drill moves as I start. I also have the challenge that the SDS drill hits the joist behind - even with a variety of drill bit sizes (150, 210 and 260mm), so a straight hole is not possible.

 

The challenge now:

 

What is the best way to join this joist, given I dont have enough clearance on the back to a hammer or imapct driver?

I need to raise the area a few centimeters and not sure how, as there are kitchen cabinets sit underneith. I though about securing some wood to the wall and jacking it up with a hydraulic jack, but given the inside wall, under the plaster is rubble I would need to secure a deep stud, possibly with chemical resin and this would be troublesome to later remove.

 

There is no easy way to this one, but any guidance or tips would be most welcome.

 

This is the kit I got to but join the joists.

 

[MikeGrahamT21]

You've got yourself a double height entrance hall there! ?

[Carrerahill]

1 hour ago, cdtsilva said:

Hi Everyone.

 

While going for a very routine sealant replacement job on my newly bought house - I noted movement - and after investigation I realized the bath was sealed with expanding foam just under the damaged sealant resulting in water ingress and extensive damage to the floors underneath. None of this was visible prior. The surveyor quote  high humidity and possible investigation to rising mould on the walls underneath, but further structural analysis would not be possible without taking things apart.

 

Presently I removed the ceilings to the lower floors covering this joist and will later remove the toilet to raise them (as it was fixed to the wall in a lower position and shows signs of leakage in the past too).

 

I will have to break the new joist into two pieces to secure it into the wall cavities at each end, but given it is so close to the wall - I cant get any nails or screws on that side to fix the joining metal plate. I considered drilling into the wall, but its 15cm or rubble till I find solid stone and often the drill moves as I start. I also have the challenge that the SDS drill hits the joist behind - even with a variety of drill bit sizes (150, 210 and 260mm), so a straight hole is not possible.

 

The challenge now:

 

What is the best way to join this joist, given I don't have enough clearance on the back to a hammer or impact driver?

I need to raise the area a few centimetres and not sure how, as there are kitchen cabinets sit underneath. I though about securing some wood to the wall and jacking it up with a hydraulic jack, but given the inside wall, under the plaster is rubble I would need to secure a deep stud, possibly with chemical resin and this would be troublesome to later remove.

 

There is no easy way to this one, but any guidance or tips would be most welcome.

 

This is the kit I got to but join the joists.

First off, are you sure you cannot slip a timber in full size? If you have a cavity wall then you may be able to insert a full length timber albeit with a slightly reduced bearing surface which could be made up for with relevant additional timber or steel bracket/anchor. I'd investigate that first. I know I could do this in my bathroom because I have a 100mm cavity. Cost of joist replacement using this method £25.

 

If that was a no go situation I'd then consider a steel route, but that is just me and I can sort out steels as easy as I can get a piece of timber! Just for thinking aloud purposes, I think hollow box section or a flitch beam which I would assemble in place.

 

The box section idea would require off-site fabrication, I have a leaning towards this sort of thing because I can easily get hold of steel and have a friend who owns a large fab shop who would weld it up for me, or to be honest, for this, I would weld it myself. Cost - £50 I reckon and I have a good solid repair.

 

Next option and really only needs a piece of plate cut to length and depth of joist and drilled. A flitch beam is basically a piece of thin steel sandwiched in-between 2 pieces of wood. This would allow you to use steel and timber and do it all DIY - you could then have a single piece of steel in the middle and then sandwich it with 2 say 1x6's you could use shorter timber and butt joint it, and then offset the other side, so you end up with one steel (which being bendy on it's side can be slid into wall, and wriggled in at the far end) then add the timbers to give you a solid twin timber flitch beam with offset timber joints. This, coach bolted together tight would be solid and cheap. That piece of steel from brundles would be about £30.00.

[Onoff]

I see a sunken bath opportunity...

[Onoff]

I favour M10 studs, square plate washers and dog washers between new and old joists. Even if it means taping nuts onto spanners to slip between wall and joist.

[cdtsilva]

38 minutes ago, Carrerahill said:

First off, are you sure you cannot slip a timber in full size? If you have a cavity wall then you may be able to insert a full length timber albeit with a slightly reduced bearing surface which could be made up for with relevant additional timber or steel bracket/anchor. I'd investigate that first. I know I could do this in my bathroom because I have a 100mm cavity. Cost of joist replacement using this method £25.

 

If that was a no go situation I'd then consider a steel route, but that is just me and I can sort out steels as easy as I can get a piece of timber! Just for thinking aloud purposes, I think hollow box section or a flitch beam which I would assemble in place.

 

The box section idea would require off-site fabrication, I have a leaning towards this sort of thing because I can easily get hold of steel and have a friend who owns a large fab shop who would weld it up for me, or to be honest, for this, I would weld it myself. Cost - £50 I reckon and I have a good solid repair.

 

Next option and really only needs a piece of plate cut to length and depth of joist and drilled. A flitch beam is basically a piece of thin steel sandwiched in-between 2 pieces of wood. This would allow you to use steel and timber and do it all DIY - you could then have a single piece of steel in the middle and then sandwich it with 2 say 1x6's you could use shorter timber and butt joint it, and then offset the other side, so you end up with one steel (which being bendy on it's side can be slid into wall, and wriggled in at the far end) then add the timbers to give you a solid twin timber flitch beam with offset timber joints. This, coach bolted together tight would be solid and cheap. That piece of steel from brundles would be about £30.00.

 

Thanks for your feedback.

 

Its a stone house with no cavity. On one side I have a single row of bricks shared with the adjoining house. On the other side I have a layer of wood, supporting the door frame and plastered wall, followed by some loose rubble. The joist sits in a piece of stone about 10cm long -  about 15cm inside the wall.  So I would not be able to fit a full size timber. as there is no support on the outside of the wall. I considered steel as an option, but that too would have to be broken down in two pieces.

 

Im considering the steel  bracket options, with bolts going straight through, rather than dilling into the wood - as tightning nuts on the end would be a bit easier. Sadly the supports I ordered (see last of 3 pictures) are just 1.5mm thick with (many) m4 holes (for twist nails). Im thinking to open those I would damage the galvanizing. Not sure if that would be a problem or not, given they are not very thick to start with.

 

I am also considering a simpler plate with M10 screw going straight through and a nut at the end. These are 2.5mm thick, but only provide support through the sides. I'm guessing this would be OK?

 

A steel fabriction is what I needed here... I can get the steel bar locally, but dont know of any steel fabricators nearby, sadly.

 

 

 

Edited October 14, 2020 by cdtsilva

[Russell griffiths]

I would just use the correct size timber but bolt it to the wall

fix the joist to the wall with 12mm studs, secured into the wall with epoxy resin

drill the timber at 600 centres, mark the wall and remove the timber

clean out holes and squirt in epoxy, fit studs and allow to go off

fit timber and tighten nuts. 

 

I did one exactly like this years ago and the customer put it through his house insurance. 

[cdtsilva]

4 hours ago, Russell griffiths said:

I would just use the correct size timber but bolt it to the wall

fix the joist to the wall with 12mm studs, secured into the wall with epoxy resin

drill the timber at 600 centres, mark the wall and remove the timber

clean out holes and squirt in epoxy, fit studs and allow to go off

fit timber and tighten nuts. 

 

I did one exactly like this years ago and the customer put it through his house insurance. 

Thanks.

I wont be able to drill straight as the drill would hit the joist just before. It's  quite a thick wal untill it reaches stone.What sort of angle would it be acceptable?