Please confirm my joist sistering plan

[renovationsnewbie]

Hi all,

I am sistering some joists (not rotten, just need more strength!)
Both joists are 120x45.

This is the plan:
One end sits in a wall pocket, which I think I'll have to cut an angle to the end of the joist to help it fit.

1) Place a laser level or string line across the two bearing points
2) Jack up the old joists (From the centre) slightly, even if not sagging.
3) Drill 12mm holes every 600mm in a W pattern, keeping at least 60mm from top edges and 100mm from ends. (potential issue?)
4) Place the 50mm toothed timber connection in between the joists
5) whack M12 130mm Coach bolts through (with 50mm square washers on both sides)
6) Tighten with a hand wrench

What do you think? I'm thinking I may struggle with the stagger pattern, I think the connectors need to be 30mm from edges. Is this the wrong approach?

Please let me know how you would do this! Much appreciated

 

[stevie888]

Overkill.

You don't need to sister the whole length as the bending stresses are biggest at midspan and shear loads which are biggest at the ends are generally low so the original joist needs no help especially if not rotten. I would personally just use plenty of woodglue and 70or80 screws.

 

[^woody^]

Stop reading about this wherever you have been reading! Presumably this is a floor, not a bridge.

Do something along the lines of ...
1. Put new joist next to existing joist
2. Whack a few nails in

 

[RrogerD]

When I did a couple of the rotted joists in the corner of the downstairs front room I just chopped out all of the bad stuff and then overlapped a couple of feet into the good. I did use coach bolts and plate washes, wrenching them up good and tight. I also supported the new pieces with bricks and a slice of dpc to avoid repeated rot.
I'm not a builder. It's just what I thought seemed good. Floor felt sound and level after so all's good.