Seems like there’s always more to do…
A few weeks ago, we took a major step forward- we are done with the walls, and we got the Ridge Pole and rafters installed. I’ve spent that past 2 weeks- in between weather events and life- getting the rafters level.
Again, if we were building with 2×4’s, it’d be easy. Building with crooked logs involves a lot of finesse and finagling to get things to look right. There is nowhere to ‘zero’ my measurements, so I have to do relative measurements. For example, the cap logs are actual logs, so they vary and wave as they go along the house, which means the rafters will do the same. The rafters, as I’ve mentioned, vary as well- but they at least have one flat side.
If I don’t ‘square things up’, I’ll end up with a crooked roof. That’s what is eating up my time. And leveling and squaring the rafters is done in 3 parts: setting them at 4′ on center, then leveling at the Ridge Pole, then leveling at the cap logs.
Setting at 48″ on center
When the crane guy was on site, we were paying him a bunch of money per hour, so we decided to just get the rafters close to where we wanted. Later, I went back with a tape and measured 48 inches from front to back, and placed the rafters on this mark. Then I did the same at the cap logs. When matching up the cap log placement of the rafters with the Ridge Pole placement, I found that eyeballing it was better than trying to drop a plumb line and squaring it up that way.
leveling at Ridge Pole
This was more complicated than I thought it would be. There are quite a few variables- roof pitch, Ridge Pole taper, ridge pole bow, rafter size, bolt hole placement, and not to mention working 30’+ up in the air. Dropping tools from that height is a pain. I ended up rigging up a pulley system and buckets and strings tied to the tools and then secured to the rafters. Yes, I wore my fall harness, which was a pain, but would have been more painful to fall.
The goal here was to get them level vertically as well as horizontally. Since the RP is so wide and has a slight bow towards the East, some grooves had to be made in the RP to drop the rafter pairs down to the correct height, and at the same time move it left or right to line up with the other rafter pairs. Cutting a groove to move the rafter left or right also drops it at the same time. I measured several of them carefully, taking note of the exact placement and diameter of the RP at that point. I used graph paper to virtually drop a few of them a few inches to see what the effect would be before I cut. Once I was comfortable with my graph, I started in on the actual rafters. I used an electric chainsaw (much lighter and easier to maneuver at 30 feet up), and then smoothed the cut with an angle grinder and a rotoclip disc.
They are now all within 1/2″ of level and center.
Leveling at Cap logs
I first took a string and a string level and nailed it to the rafters on each end. Then I measured the difference between the height of the string and where it touched the rafters and recorded it in a notebook. The rafter that is furthest away from the string is the lowest, so the next step is to make all the other ones match. Unless they vary by a lot. In my case, the East side of the house varied by 8 inches across the rafters- because it kind of sags in the middle. We knew the m when we put the cap log up, but we didn’t know it was 8 freaking inches. All four corners of the house are within an inch, but it’s the ends and the middle that matters, and that’s where the difference was. There was no way I could cut 8 inches out of a 13 inch cap log- that would weaken it beyond use.
To overcome this gap, I jacked up the most offending rafters and installed two 4″x5″x14′ beams that I made on the sawmill and pinned them with rebar. This won’t be seen when the roof is on unless you know where to look because there are other boards called bird blocks that go exactly on top of the beams.
On the west side, I overcame the issue much easier with a 2×4. The rafters rest on these “jacks”, but they are still pinned with rebar through the jacks and into the cap logs.
They are now all level to within 1/2″ of each other.
Before we can install the decking on the roof, we need to install our girder log. This log acts as a ‘collar-tie’ for those in the industry. For non-industry types, the girder log keeps the walls from spreading when the 80,000 lb roof is installed. The girder also holds up the second floor. It can be installed at anytime, once the wall logs reach over the second floor. Those using telehandlers usually install it right when the wall logs reach second floor height. When using ropes and pulleys, it’s easier to wait until the wall logs are done so you have somewhere to hang the pulleys.