how to repair a pair of rotten joists?

[ajrobb]

I originally posted this in Building but got no replies.

I have a pair of 165x45 joists which are rotten up to 800mm from the supporting wall. The paired joists are bolted together with 3 coach bolts along their 3.6m span. The rest of the joists are single 165x45 at 400mm centres with wooden herringbone trusses mid-span.

How can I repair this pair of joists?

 

[ladylola]

A picture may help.
If I'm reading this correctly then the two joists are full lenght at 3.6m span bolted together to form a 90mm joist (like a thickened trimmer?) and are rotten at one end?
The simplist method would be to cut back one joist say1500mm and the other at least 2m and replace with new timber bolted into place. This in effect is giving you a lap joint of a metre.Steel timber connectors may also be a good idea.
Alternatively is it not possible to simply replace the whole lenght of the joists? It's offten much quicker, cheaper and easier not to mention stronger.
Also don't forget to assertain how the rot has set in and remove any sourch of water which is a likey problem.

 

[ajrobb]

A picture may help.
If I'm reading this correctly then the two joists are full length at 3.6m span bolted together to form a 90mm joist (like a thickened trimmer?) and are rotten at one end?
The simplest method would be to cut back one joist say1500mm and the other at least 2m and replace with new timber bolted into place. This in effect is giving you a lap joint of a metre.Steel timber connectors may also be a good idea.
Alternatively is it not possible to simply replace the whole length of the joists? It's often much quicker, cheaper and easier not to mention stronger.
Also don't forget to ascertain how the rot has set in and remove any source of water which is a likey problem.

I've been trying to upload pictures for days - now it works

Untitled

• ajrobb
• 15 Apr 2010
• 2

The rot was caused by the first bath's seal failing. No bath (no bathroom) now. Will be enlarging bathroom after joist repairs.

All the power cables run through holes on the centreline of the joists. I don't want to rewire the house.

Decided to go with the lap joint (glued and bolted) plus steel splice plates.

I want to replace the rotten floorboards and a few more with a single sheet of 18x1200x2400 cement bonded particle board under the bath and partition.

 

[foxhole]

Just bolt another pair either side.

 

[ajrobb]

Just bolt another pair either side.

The first wire hole is about mid-span (1.8m from wall). I'd have to cut slots down to the wire holes in additional timbers to get them in place without rewiring. Also, I'm not happy about keeping rotten timber.

 

[foxhole]

Move the wires up so you only have a shallow notch in new timber.

 

[ladylola]

Or cut and reconnect with a junction box.

 

[ajrobb]

Or cut and reconnect with a junction box.

Are hidden junction boxes best practice?

 

[squern]

I don't hide mine I let 'em dangle.

 

[ajrobb]

I don't hide mine I let 'em dangle.

I wasn't talking about boxers.