repair roof truss

[Tomdickorharry]

I wanted to move the loft hatch into a more convenient position so I cut a section out of the ceiling tie of one of the roof trusses - about 3 feet long from the middle of the W. I boarded the floor over & put lots of stuff in the loft & so far it's been ok but I now realise I have done a Bad Thing. Please help me fix this before I have to post in DIY Disasters.

What I would like to do is replace the missing section of wood & put another piece alongside to strengthen it & also double up some of the other ties while I have the loft boards up.

I was going to butt joint the new piece with the existing piece & join them with nail plates (which are what the trusses are put together with). Is that best?

How should I fix the new pieces alongside the old? I have an idea that nailing is better than screwing because nails push the wood aside rather than cutting it & similarly drilling holes for bolts is another Bad Thing. If double-sided nail plates exist, would they be best?

What sort of wood should I use? The existing ties are 35mm x 130 & I was going to use the same. Should I use C16, C24 or something else?

Thanks

Tom

 

[chappers]

Cutting any part of a fink truss is really a no-no and not something I would reccomend,but to be perfectly honest if it is just the one then you will probably be ok.
I once went to look at a loft conversion and several of the supporting members of several trusses had been cut, when i mentioned this to the guy he said they had been like that since he bought the house 6 years ago and there seemed to be no real harm to his roof.
But as i said not something to be reccomended.

 

[Tomdickorharry]

It worries me though. I had my doubts at the time but had read things which led me to believe it was ok, not knowing the difference between the old-style rafters & these engineered-to-a-whisker trusses, so I just said that phrase so popular with candidates for the Darwin Awards, "I'm sure it'll be ok" & went ahead.
But it's been nagging at me, more so since reading about it & coming across warnings like "never ever" & "under no circumstances" so I'd like to get it patched up & if possible strengthened. Besides, the hatch is in the middle of the biggest space in the loft so it wouldn't be so bad to move it.

 

[PaulJR]

You could simply trim around the hatch with something like 4"x2" or even 6"x2" and tie both sides of the cut tie to the trimmers.

If I understand you correctly you have cut a piece out of the centre? - this is a purely tension member so if you want to repair it get a set of BAT repair angles. Screwfix do them for less than £5. They need all holes filling with nails - should be included.

http://www.screwfix.com/prods/69624...work/Splice-Plate-Kit-18-X-57-X-400-Pack-of-4

 

[PaulJR]

What I would like to do is replace the missing section of wood & put another piece alongside to strengthen it & also double up some of the other ties while I have the loft boards up.

Existing tie is 35x130 - a Ex4"x2" (97x47) is equivalent - I wouldn't worry about grade.

How should I fix the new pieces alongside the old? I have an idea that nailing is better than screwing because nails push the wood aside rather than cutting it & similarly drilling holes for bolts is another Bad Thing.

Nailing is simply CHEAPER than screws, there is no problem with either. TRADA who are the people who know about such things recommend that screws of more than Ø5mm should be pre-drilled. Other than that they are the same from design standpoint, they are considered "dowels"

 

[Shytalkz]

You naughty, naughty man!

Just the one would probably be ok without remediation, but what's proposed above will be ok for you to start sleeping again at night

 

[Tomdickorharry]

I did trim around the hatch with 4"x2" going between the parallel uncut ties and tied both sides of the cut tie to the trimmers.
Thanks for your replies chaps. Looks like I was worrying too much but I will repair & strengthen it, then I can put even more stuff in the loft.