Re-levelling first floor joists - Lift vs drop joists? Do nothing at all?

[JamesSmith79]

Hi folks,

I have an admittedly crackpot idea to level the first floor in a doer upper I have. There was a significant leak some years ago in the property which caused the center to settle a couple inches but it has since been underpinned there with mass concrete etc well before me.

The issue I am having is sloping floors upstairs. The drop is up to ~70mm at worst (Probably over 4m). Under foot it actually doesn't feel the worst but as I am doing a full renovation here I thought now would be the time to sort or never at all.

 

I have looked up all options related to sistering, shims etc. One idea that was proposed to be was to make the high sides (external walls) lower as opposed to the other way around. The joists are all pocketed into the block cavity and mortered in. Then the other ends are pocketed into an internal 100mm block wall that goes up to second floor ceiling (5m or so) The idea is essentailly to cut pockets below every joists and drop the joist down. This will lower the floor and even out the slope.

 

Bar that one block wall in the middle, all the others are partition stud, so either should fall with the floor or stay on the ceiling. Both would be repairable.

 

Is this absolutely an off the wall idea or possible?

 

This is idea A, idea B is even more drastic. This 10m wide, 5m tall wall is holding the first floor joists so lifting the joists is impossible. What if a consaw was used to cut near the ground floor ceiling. Obviously using acrow/strong boys to support as we go. This would unlock the wall and joists above. Now we have an 8ft wall below and an 8ft above. Then from below we could jack up the first floor joists and wall....somehow.

 

My crude drawing. Two external cavity walls with one standard internal 5m (Both floor) block wall.

https://freeimage.host/i/FAZOkEx

 

 

[Gus Potter]

@JamesSmith79

1 hour ago, JamesSmith79 said:

I have an admittedly crackpot idea to level the first floor in a doer upper I have.

This is the great thing about BH when folk like you come up with ideas. It's not "crackpot".. it's just you asking a perfectly reasonable question. 

 

1 hour ago, JamesSmith79 said:

all the others are partition stud, so either should fall with the floor or stay on the ceiling. Both would be repairable.

Ah.. but the building has probably settled a bit and the roof timbers are used to the loads.. you need to look at all the load paths and how they might change when you drop the timbers

 

As a heads up..  it's an old roof, maybe the nails and fixings are corroded. You are going to change the load paths and change the stress pattern. 

 

While in principle your idea is good you need to look at the knock on effects. 

 

Your idea is elegant.. provide you can justify it is not overloading other parts.. call that unintended consequences. 

 

You mention "strong boys" For all on BH these tend to have a maximum working load rating of 350 kg or less.. which is not a lot! I can tell you as an SE that a lot of builders have no idea how llittle load these can carry! Always ask a builder if they know what they are doing when they mention strongboys!

Edited Friday at 22:24 by Gus Potter

[ETC]

Why don’t you just lift the boards and put firing pieces on? Simpler and cheaper.

[JamesSmith79]

Thanks for the comment Gus!

 

You are absolutely correct, the building has almost certainly settled a bit. I don't believe ONLY the center went down in the last 50 years, the external walls must have settled even a fraction over the last 50 years.

 

If I went with idea A (Cut pockets under joists into external wall(s) cavity leaf so joists drop down.) I can't see how any load paths would change too much. This is on the presumption of all the partition stud walls upstairs not actually bearing anything and only this centre block ground-to-roof bearing wall.

 

Now idea B is where load paths definitely shift. This central bearing masonry wall will literally be lifted roughly 60-70mm at worst. There is a beam directly on the end of this wall in the roof so an element of the roof would raise.

 

A further element complicating all of this is two presumptions; A) That the house was ever 100% level. Were all walls always totally level? Were joists level? and B) determining where everything is right now. If the back external cavity wall is down 20mm itself as an example, then this has to somehow be factored into idea B if any lifting was to be attempted.

 

Say I could somehow calculate this, even attempting idea B would be tough.

 

Disconnecting the top half of the wall from the bottom would be the easy bit, how would one even lift? One dea would be to just put a beam adjacent to the wall under the joists and lift. This though is relying on the 2" of 7x2" on 12" centres literally lifting an 8ft wall above, not to mention the portion of the roof, the joists etc. 10m width/304mm centres is 32/33 joists for the length of the house. That is roughly 1700mm of joist end coverage width "touching" the wall. So jacking the joists would mean lifting directly 17% and hoping it will take it all. Thats not taking into account the strength of the wood, how deep its actually pocketed into the wall etc.

 

Another option would be to support the cut wall above (With a lot of stongboys!) and every x m pocket in a bottle jack into the lower wall to directly lift above. 

 

 

[JamesSmith79]

4 minutes ago, ETC said:

Why don’t you just lift the boards and put firing pieces on? Simpler and cheaper.

 

Thats absolutely an option but for a 70mm lift, surely that will make things tough with doors etc. Everything will have lost 70mm at floor at the lowest point. This just so happens to be where the doors are. There are a few doors in this masonry center wall. How would one rise those 70mm?

 

I actually thought the idea of dropping joists on one end could be cheaper and quicker but probably not. If this was easy other people with similar issues would do it. I haven't seen any example online of dropping down joist ends!

[Gus Potter]

2 minutes ago, ETC said:

Why don’t you just lift the boards and put firing pieces on? Simpler and cheaper.

Agree. 

 

From an SE view the roof will be restraining the old walls. Once you start to muck about you could break these established bonds and risk things starting to move. 

 

When working on old buildings we need to be careful that when we stengthen things we don't inadvertently cause harm. 

[ETC]

Once stayed in a hotel/b&b in Canterbury - not a level floor in the whole building - was grand.

[Nickfromwales]

3 minutes ago, ETC said:

Once stayed in a hotel/b&b in Canterbury - not a level floor in the whole building - was grand.

I stayed a good few times in the Chapter House in Salisbury, a proper steak house to say the very least.

~13th century building, and the staircase going up to the rooms was like that perpetual staircase where you seem to go down or sideways and not up! Great if you don't want a drink as just walking up the staircase to the room makes you feel like you've had 9 pints  

 

If anyone likes steak, and you're passing by there, go get some of the best beef you'll ever eat  

[ProDave]

We once tried to buy a wooden bungalow with a subsidence issue years ago.  It looked like the subsidence had stopped and it had been re roofed with a custom cut roof that corrected the previous wonky roof but the building had been left with one outside wall that had clearly sunk leaving one room with a sloping floor.

 

Our plan would have been level that floor and do nothing else, and in the longer term it would have been knock down and rebuild.  But we were outbid and it sold for more than we though it worth.

[Temp]

Would dropping the joists at the outer ends put stress on any wiring or pipe work?

[Nickfromwales]

3 hours ago, Temp said:

Would dropping the joists at the outer ends put stress on any wiring or pipe work?

I tried jacking a floor up like this before, and it was like fighting against dark matter. After decades and decades of progressive deflection, you just cannot fight natural timbers et-al back into shape over a long weekend. Give it up IMHO.

 

Furr the tops of the joists and pack & level the ceiling and re-board. Sistering the joists is my favoured method of levelling up a 1st floor bathroom floor before installing a new wet-room / level floor for tiling etc, and that is usually the best option. 

 

If the floor is say 50mm out end to end, I will sister the high end with the new timber 25mm down, and glue and screw the joists together to act as one, and then electric plane the original timber down to meet the new. Moving one end to take up the 50mm.......not whilst I have a hole in my box of holes.

[Dave Jones]

could just accidentally burn the place down and get a new one!

 

https://www.bbc.co.uk/news/uk-england-stoke-staffordshire-68414524