Levelling old joists by sistering

[nitro23456]

Hi guys

Victorian house, sloping floor to one corner of room. Room approx 3000 x 2800 Current joists 200 x 50 at 300 spacing and seem sound. 10 joists in room with a span of approx 2800. Some movement in the walls years ago has caused the slope.

Question 1 is, is it ok to sister new 150 x 50 joists for approx 75% of original length to these to level out. i.e smaller than the originals to make it easier to get them in. Then chipboard floor on to new with load transferred on to old?

Question 2 - planning on M12 coach bolts, what spacing?

Question 3, is this notifiable?

 

[bobasd]

is this ground floor?what was the movement that caused the drop. were you ther when it hapened? how do you now if the joist tails are soundand not rotted?

on the face of it your plan is well sound.
no need for BCO.

 

[cdbe]

My "method" is to cut 18mm ply or OSB into long strips and screw/nail to both sides of the joist. Like an I beam in reverse and much cheaper and easier than new joists.

 

[pilsbury]

5x2 or 6x2 have got to be less than a tenner for that length. Wouldn't fancy screwing into the end grain of ply or OSB.... With a mere 18mm width..... Of which you need to hit dead centre.

 

[nitro23456]

Thanks for the replies. I think il go with the 2x6 method.

Any thoughts on coach bolt spacing? Down the centre or in pairs?

 

[endecotp]

Another option is to cut long wedges of timber to fix on top of the existing joists.
The challenge is how to make them, with whatever tools you have available. There was a thread about doing this for something in a roof a while ago. I think the answer was to find someone who can do it with a bandsaw.

 

[phatboy]

I was recommended 300mm spacing, with dog washers, and one bolt high, then one low etc

 

[cdbe]

Looks like the op is sticking with the sistering option anyway but for what it's worth the screw/nail goes into joist not ply:

 

[oldbutnotdead]

My "method" is to cut 18mm ply or OSB into long strips and screw/nail to both sides of the joist. Like an I beam in reverse and much cheaper and easier than new joists.

View attachment 144858

Used exactly this technique on a similar sized room (where one corner had dropped due to movement a long time ago). It has worked well so far (only been down 6 months so no clue on long-term durability). I actually used 25 x 150 rough sawn treated cladding- dirt cheap and fairly decent timber- since doing it in ply was going to cost a fair bit more. Once I'd fitted the side bits I nogged them with 3 x 2 to reduce flexing

While you've got the joists exposed, well worth nogging them- also consider nogging your new strapon 6 x 2s as well, it'll reduce any flexing caused by the nature of the loading.