How To---splice A 5"x7" Glue Lam

grsr3

I have a situation where there are 7 architectural trusses spanning the main living area in a home. They are 35' long and the ends run to the outside of the house. The top chord of the truss has the end grain completely exposed to the weather. Three of them have rotted out. I have purchased a 6' length of the top chord material (5"x7" glue laminated pine). Need to find the best way to cut off the bad ends (some as deep as 18") and attach a new section. Above the trusses are 2"x6" tongue and groove beveled-edge pine boards that run across the trusses forming the interior ceiling and the roof deck. The trusses are 6' apart. The roof deck material is nailed to the top of the truss, so when I cut away the old piece of truss the roof decking running over it will not be fastened to anything. I need to join the new section of truss to the existing section and also fasten the roof decking to the new section of truss. I have some ideas but they seem pretty difficult to do. Lapping the truss material together and lag bolting is one idea. Not an easy job to get the cuts clean and straight working upside down under an over-hang 8' off the ground. Any ideas????

fettycan

sounds like the roof mite be leaking or ice damage? wood it be possible to remove roof deck to the wall and try to hide splice in the 4 or 6" where wall meets the roof?

karma_carpentry

They say a picture is worth a thousand words. I see you've posted your pictures at DIY forums so here's the link:

http://s58.photobucket.com/albums/g271/grsr3/

It will help people here to understand just what the end of the top chord is at in relation to the rest of the truss.

At first glance, I see that it's holding up the overhang, which could be a substantial load. You don't have your location in your profile, but if you're in snow area, you've got that. Anyway, the overhang should be fairly strong in principle.

I don't see how a simple butt-joint of the same 5x7" glue-lam will have the required strength. They're on 6' centers.

A bolted lap-joint seems like a decent option to me though much better if the top lap is attached to the overhanging new piece, which would be really hard to install without fully removing the roof decking.

How bad is the rot, really? If it's not too bad and doesn't extend up too far with any serious structural effect, then could you soak in a wood hardener, and then scab on a very small cross-section of the material to make the ends look okay? Or do some other cosmetic fix? Are you fixing it for structural or cosmetic reasons?

Maybe consider a clear penetrating epoxy sealer before any cosmetic fix.

I don't like to leave any substandard wood in place, but in this case the amount of work may not be worth the benefit, but only you and your customer can really answer that based on many variables but mainly the current strength of the glue-lams in present condition, and the required load carrying capacity of the overhang.

fettycan

thats not a easy fix ! But I can live with it just the way it is!

grsr3

Hi Karma,
Thanks for the reply. I believe I have the water problem solved. I got some copper sheet goods and cut up 14 pieces about 1" bigger than the rafter ends. Going to get the best (longest lasting rated) caulk and seal the ends and around the edges of the ends and tack the copper over and around them so that the sealant squeezes out. This should keep them dry for a good long time. Only one end is really bad. It is almost completely gutted up the center for about 15". The outside surface is still OK, but almost paper thin in some spots. I was thinking of packing the hell out of it with cement or something rot proof then sealing over that with the copper. The others are rotted just a few inches deep. I could cut those clean and butt join them with counter-sunk lags, then stain to match and seal. What do you think?
Geo.