Joining two timbers together, what size coach screw to use

[dx90]

What I've decided to do is acro prop the bedroom ceiling/floor in loft up straight to take out the sag in the 4x2" joists and put some steel straps from each joist to the pearling to keep it there. Then I’m going to put some new plained red wood 4x3” 13 feet long from the main bearing wall to wall plate at 90 degrees to them and fix a coach screw down through the new to the old joist on every joist to tie them all together. Its only going to be used for storage.

My question.

What size coach screws to use to go through the new and into the old joist far enough to give good grip?

 

[Robert too]

If i read that correctly , you are basically going to hang the sagging ceiling joists from the existing purlin ?

Then put a binder in above them.

I suspect you will just induce sag in the roof when you unwind the accros.

 

[dx90]

Yes from the pearling.

Not a single binder though, a complete floor made of 4x3" joists @ 90 degrees to the old.

Then join each new joist with old @ every cross over with coach screws to tie it all together.

Does this sound ok to you?

What size coach screws do you suggest I use?

Thanks

 

[Bowness72]

As Robert too says, you are probably going to damage your roof if you do that, unless the purlins are significantly bigger than they need to be, which I doubt. There is also a chance that the steel straps will break.
Obviously we are saying this without seeing the full picture so there may be some reason we dont know about that will make it work.

 

[TDBOY]

Try putting a binding timber across all the sagging timbers to equalize the weight a bit better. Make sure that it spans all the joists across the room and plus some in other rooms . Also fix timber ties from the perlin to binder. This will spread the weight.

 

[Deluks]

The purlin(ing?) is for supporting the roof. If you add the weight of the ceiling below, and add a new floor to that, you are going to end up with too much weight bearing on the purlin, from above and below. It would be wise to hold off your plan until you can get some definitive advice from someone knowledgeable. You shouldn't really be messing about with roof components that you can't even spell

 

[dx90]

The purlin that I'm going to fix the straps to runs across the apex in the roof at the front on my house and this is where I want to strap the joists to. There are no roof timbers resting on this part of the purlin because the apex is above it.

Do you think this will be ok?

Thanks

 

[Deluks]

The purlin that I'm going to fix the straps to runs across the apex in the roof at the front on my house and this is where I want to strap the joists to. There are no roof timbers resting on this part of the purlin because the apex is above it.

Do you think this will be ok?

Thanks

I'm still confused, what is the purlin resting on then, what is it attached to, what's holding it up?

 

[masona]

Do you think this will be ok?

To be honest I think you're wasting your time, you will do more damaged than good. Once the timber has settled over the years, it will not go back to the correct position and it will put on extra pressure on the wallplate side pushing upward. There's maybe a ceiling binders missing so you will need to put one in and use strap hangers to tie it in.

You can either put in a false ceiling just underneath it or take out old ceiling (messy) using thin strip timber to pack it out under the joists or using using 6"x2" joists notched out over the wallplate side by side of the ex-joists so the bottom of the joists is lower.

 

[dx90]

I will put new floor in on top of the old joists to tie them all together without trying to take the sage out and put a false ceiling in below and save all the mess. There is only going to be light stuff stored up there. Also put some binders in.

Thanks all for your advice and help.