Floor joists - holes and bolts

[DaveJ123]

Hi,

Sorry if this has been done before...

I want to 'bolt' a new piece of floor joist to an old joist which is rotten in the middle. Do the bolt holes need to be horizontal? I don't want to hire/buy a 90 degree drill if it doesn't really matter.

Also, what to use: M10 studding, coach bolts?

DaveJ

 

[Mr Ben]

The bolts definitely have to be at 90 deg due to the shear forces acting on them and the strength calculations involved. The size of bolt and quantity will depend on the size of joist. You need a structural engineer to advise. NB. May not cost as much as you think!

 

[Mr Ben]

.....there might even be one on this forum????

 

[DaveJ123]

Ok thanks. Most disappointing! I was looking for re-assurance since in addition to complicating this job, we've already had a builder (working for an ISO registered company btw) repair a joist in another room that way.

The new joist is 47 x 100 mm and the damaged one, in this case, is quite a bit thinner. It's a few inches inside, and parallel with, the wall.

DaveJ

 

[DAZB]

It may depend on how much of an angle you need to go in at really , yes technically the strongest situation is with the bolts going through totally level but if you are within an inch of level then I would increase the number of bolts and add timber connector plates to compensate. This is a connector plate :
this
Remember to use a washer with the bolts and you will be ok

 

[markf]

90 degree drill only costs about £20 to hire from HSS. Buying one would set you back £200.

 

[DaveJ123]

Yeah, thanks. You can get 'em cheaper than that, but I've found an angle drill attachement for £18. (toolshopdirect.com). It's *not* one of those flexible things. Tested it out briefly, and seems ok. Will let you all know how well it worked when I finally get around to doing the job.

DaveJ