THE BARN ROOF REPAIR PART ONE-THIRD
Halloween had come and gone and the weather changed quickly. The warm days turned cold (Yay!), the daylight turned to dusk, and the long summer drought finally ended with an average of one nor'easter per week. As I write this on the ninth of December, we've had seven in four weeks. One's on top of us now, and rivers are climbing their banks.
The cheap cover for my outdoor kitchen proved to be nothing at all for the first one.
Knowing the winter was fast approaching, I knew I'd need some more workspace. So I deconstructed the wood cookstove in the machine shop, moved it to the greenhouse, and built my first permanent built-in workbench. One that could handle long pieces of trim and other wood to be cut by my chopsaw, on top of the table saw in this pic.
Now was the time to tackle the barn and get it ready for winter. The lesson with the blue canopy was not lost on me; one good snow load on the barn roof, and say goodbye. I knew I couldn't replace the roof all at one go, so I did the most I could in a short time.
Swayback barn before I pulled in the wall of the right section. If you don't recall, the right third is circa 1860 and the left two-thirds is a completely independent structure built in the 1700s, likely around 1710, if the stories and archaeological evidence are to believed. In this picture, taken in early summer, the wall of the right barn was being pulled in. Go back and read about it in an earlier post.
It's okay; I'll wait.
Dum de-dum, de-dum...
Right. All caught up? Good, you forgetful cretin. Let's continue.
I wanted to work on the right barn roof, but was compelled to stop any outward movement of the left barn wall first. The brace to the right is temporary at best, as the rafters that support the roof are pushing it out. The barn should have been built with joists or a second-story loft structure tying the walls together, but this was either never done or the loft is now gone. There is actually no evidence of a loft having been there. The wall below the brace has moved out almost sixteen inches. It is very stable; no amount of pushing or pulling can budge it. But in time, it will come down, taking the rest of the barn with it.
I decided to tie together the plates upon which the rafter ends sit; made of 8x8 chestnut, the one to the north was completely intact, while the one on the south side (in the pic) was nearly completely deteriorated at the mortise that holds the central vertical support's tenon. Whew! I hope that was as hard to read as it was to write. This side of the barn has a corner post to the left, a corner to the right (just to the right of the door), and a center pole that is actually a tree, rounded with a tenon, sitting on a rock. That is the weakest point in the barn.
I braced the central vertical support by tying it to the central beam (bottom right of the pic) and sandwiched the plate between two pieces of 2x. I connected the pieces with two sections of 3/4" threaded rod and an eye bolt. Large washers spread the load. The diagonal brace will have to be loosened and repositioned when the wall is moved in.
Doubled 2x6 plate on deteriorated south plate. This 2x doesn't have to run the entire length of the plate; it's the longer one on the outside that carries the load. The pulley on the come-along hook doubles the pulling capacity of the machine. Increases it, anyhoo. You physics majors put your faces back in your books. The 2x4 scab is there to support the rafter end, above the most rotted part of the plate. Note how it has dropped in relation to the others. The roof sags badly at this point, which is directly above the central vertical support. The cable should keep the barn's south plate from moving over the winter, although I'm keeping the exterior brace in place (as well as adding a few more this week).
Looking down at the Old Barn floor from the loft. The plan is to build a scaffold in the center of the barn and set up a support system for the north roof, which will have to be jacked into place, removing the sag in the ridge and allowing the rafters to come back into place. The south wall will be pulled into position at the same time, then the north rafters will be attached to the south rafters at the ridge by plywood gussets and the south plate will be repaired and rebuilt. The central support will be repaired (likely sistered onto) and the rafter ends tied to the repaired plate. The jacks will be removed and the whole building will collapse as all will be kilt in the demolishments.
No, NO! That's not what I meant at all.
What, you don't think it will work? Let me show you how.
Before jacking the east barn (New Barn) roof, I needed to remove the rafters and support them, then pull in the south wall. I did that a post or two ago. I also rebuilt the corner post/plate joint at the southwest corner. The pic above was the condition of the same joint at the northwest corner. The southwest corner had dropped so far as to split the beam where the tenon goes into the post's mortise. Nothing could be done to correct this, as the loft from which I was working was built after the barn itself, and the structure of the loft dictated what could and could not be pulled together. So I added some 2x L-brackets as corner braces and installed a triangular 3/4" plywood gusset to keep it from moving further.
All the time I had been working on the front wall during the late summer, I had the rear roof structure supported by a 4x4 post, here moved and ready to be replaced by jacks. Note the diagonal 2x6 on the rafters. The upper jacking plate has been offset from the support structure below; I didn't want to LIFT the roof, just to move the back section to the north, dragging the now-loose south rafters with it as it went up naturally. This meant I had to jack on the diagonal, a tricky thing to do.
In addition, I had to jack the northwest rafters ends at the north plate, as their ends had softened and they had dropped. I installed some sisters and ran a new 2x6 drop plate onto the existing plate (the sisters are in the pic but the drop plate is not) after some light jacking (stifflegs are in place). Next I had to remove the small sections of wood that joined the end rafters of two barns. If I didn't, the lifting of the right roof would carry the left roof with it. The evidence that they are two separate barns is obvious in this picture. Different sized rafters and centers, different roof sheathing, and an offset in the plate ends (hidden somewhat by a piece of wood nailed to their faces). Note the plaster stripes on the scabs that join the rafters of the New and Old Barns. Typical that they would have been recycled from another building. Yankees never waste anything. That goes for me, too.
This was the barn roof as I began jacking. Note the VERY slight height difference along the joint, at the left side of the roof hole. I had barely tightened the jacks into place at this point.
The initial jacking system. One hydraulic 8-ton on the loft plate for the lowest end, and one large 20-ton screw jack placed above the central loft plate below the floor. Stifflegs are always in place and constantly being moved tighter or supported with extra 2x blocks below. This keeps any jack failure from becoming disastrous. Jack failure can still maim or kill, however. It must be done slowly, with an eye on the jack's alignment at all times. A well-trained person can feel when jack has enough pressure on it, will shim his stifflegs, then removes the jack and repositions it. Note the jacks are positioned at an angle to move the roof back, not to lift it UP. Do not try this at home. Or anywhere else, unless you've done it a number of times.
At the end of the first jacking, I have the roof up by almost five inches. The gable end has not sunk, so it is only the west side that needs jacking. This roof has no ridge plate (known as a ridge pole) between the rafters at the peak. The older barn in the background DOES have one. I tied the rafter ends together with blocks of 2x4 loosely screwed to each rafter with one screw. This would allow independent lateral movement of the rafters as they were moved back to the north.
At dark, I left the jacking for another day (three weeks, actually). The ridge still has considerable sag, but it is coming up. Note the 2x4 scabs on the ends of the original rafters; they keep them supported while the roof is lifted backwards and also gauge the progress though comparative measurement along the plate.
Plywood gussets were made and installed, but initially only screwed to one side. This last set of three rafters were recalcitrant, needing another jack to get them back into place. Note the gap in the sheathing/roofing above.
The roof pushed up and back as much as I deemed possible/necessary. I had some slight adjustments to make to the middle at this point. The rafters, sisters at eight feet long, are in place. I decided to add a small overhang to the roof to allow for the use of gutters.
Almost nine inches higher, though it doesn't look it.
Tying the rafter ends to the plate.
Screw in the gussets and rafter sisters, then remove the jacks. A slight creak was heard, then....silence.
Only the stifflegs supporting the Old Barn Rafter are still in place, and will remain so until that roof is jacked. THAT will take all winter and a bit of spring. It is a HUGE project. The New Barn roof was just practice.
