Sistering joists

[robert a]

Hi im after some advise re floor joists
.
My cottage was built around 1890 and the floor joists in upstairs bedroom have sagged.

I'm not surprised they are approx 7 x 3.5 at 18" centre's and have a free span of just under 6 mtrs!

i want to level up the floor in the bedroom, my intention was to sister them with a new 7 x 3.

i know technically they are tiny for this span but i need to match the floor level of neighbouring room.

i would also be concerned with adding too much extra weight with taller thicker joists.

i have thought about engineered timber joists but i they will be too tall also.

any suggestions would be greatly appreciated.

 

[tony1851]

First of all, you won't be able to straighten them, if that was your aim?; they will have a permanent bend.
If you remove the floor boarding, you can screw the new joists to the sides if the existing joists with 100mm x 6 coach screws @ 200 centres, staggered near the top and bottom. You can stop the new joists a few inches short of the supporting walls - they don't have to go into the walls.

The additional weight won't make any practical difference because in effect you will be doubling the section size of the joists, thus making them approx 110% stronger.

 

[Nozzle]

Also, use these

Double Sided Timber Connector

• For bolted timber connections• 1mm thick galvanised steel

www.toolstation.com