How do I manoeuvre joists up to existing rafters?

[diyAlex]

I have a garage that has rafters but no joists. It's been like that forever (well, since before we moved in, anyway). The roof has asbestos tiles covering all of it.

I want to add joists to stop roof spread and to provide some storage space - see the picture: it's the red and green that are the intended new bits, everything else is already there.

Sketch showing joists + flooring

• diyAlex
• 28 Mar 2011
• 1

How do I actually manoeuvre the (red) joists in to place? It looks like the obvious way is to slide them in from the outside - trouble is I don't want to disturb those asbestos tiles!

I did think I would be able to offer them up from the inside and utilise the joist spacing (510mm) to wiggle them in to place. But as I've modelled this in 3D, I now can't see a way of actually achieving that!!

 

[DAZB]

Tricky one but one way is to join them in the centre and splice more timbers on each side of it like a splint using spiked timber connectors and coach bolts but this would use three times as much wood. Another way would be to rip down a sheet of 25mm ply to a width that runs a few inch below the wall plate and butts right up to the underside of the felt and cut out accurate notches for the rafters. Do enough for the full length. This can then be fastened to the wall plate and even the wall (hence the extra depth) and this gives you a strong flat face for you to fix joist hangers to which will be able to carry ceiling joists. If you use a fairly deep joist you could sit it directly below each rafter and screw through it into the rafter to tie it all together or if you offset the joists from the rafters they could be tied to the ply panel using truss clips. I'd draw it like you have but I'd be here all year trying that.

 

[jbuk]

I've just replaced some large joists to my kitchen ceiling and to my attic, I found I had to cut away some brickwork to get them in the kitchen bit, the attic wasn't too bad though and I was able to wiggle them in by lifting them in at an angle

maybe buy or get hold of some wood of a similar size and test if you can get them in?

 

[big-all]

ok its only my workshop and the span is less than 3m but these 3x2 timbers willl happily support my sons 9 stone

picture 5 shows 12mm ply triangles at each side on both sides to make a triangle or a few inches up and make an "A" frame
http://s21.photobucket.com/albums/b...gall2005/?action=view&current=workshop005.jpg

 

[diyAlex]

Thanks for these suggestions guys - appreciate the help.

And I'm loving your workshop big-all !!

Take a look at that long window on the facing wall of my model - there's really no blockwork above it, just the wall plate! And I think that gives me a big problem because there's nothing for a joist to connect to other than sitting on the wall plate.

Nice suggestion jbuk about a test piece - I might pop down to wickes and find a naff bit of 3.6m something to have a go!

So I think that leaves me either with splicing the joists together as per Dazb's suggestion - it's a 3,600mm span so I'm not so sure about this.

Or removing some of these asbestos tiles after all! If I did this I would take out the lowest row and then roll back the felt to expose the wall plate/rafters and then just slide these babies straight in. I can get some slate from the reclamation yard and affix these back in place of the asbestos (I've done similar in replacing broken slate on the main building's roof).

Not entirely sure if these tiles will be that easy to remove though !!??

 

[WestmidsChippy]

i don't get it

can you not just measure the span, cut the joist 10mm shorter to start off with, cut the bevel cuts that need to be cut, offer it up and if it don't go take a tad more off?

Eventually they will fit, don't like the sound of splicing floor joists. never a good idea.

 

[diyAlex]

I think I see what you're getting at WestmidsChippy ... the bit I'm getting lost at is where you say cut the joist 10mm shorter than the span. This is probably caused by my ignorance and unfamiliarity, so sorry about that.

The reason why I'm confused is that the joist is going to have to sit on the wall plate, so I don't see how it can be shorter than the span.

 

[misterhelpful]

Basically, I think what WestmidsChippy is saying, is that the new joist doesn't have to reach the outer edge of the wall plate.
So, you can cut the joist 10mm shorter than the distance between outer wall plate edges and if it still won't fit you can nibble away a bit more until it does. There will still be plenty of the joist resting on the wall plate. Unless, of course, you have a very narrow wallplate.

At least I think that is what he means!

 

[ladylola]

Do the joists have to sit on the wallplate? You could always cut them between the wallplates and fix with hangers adding aditional straps and /or ply sprockets if you are still worried about spread.

 

[diyAlex]

Thanks everybody!

I've decided to nibble off as much length as required to finally be able to get on to the wall plate. Take a look then and decide if the overlap is sufficient. If it's not, then raise the joist up till it meets the rafter and affix with coach bolts.

Options for fitting the joists

• diyAlex
• 14 Apr 2011
• 1

One joist on the wall plate. The other just has been cut to a length that fits inside the wall...