Leveling Rafters

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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.

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How far off level are the rafters from each other? Each letter represents a rafter pair. The top line represents how far from vertical they are. The center measurements (marked “E”ast or “W”est) show how off-center they are horizontally. The bottom line represents how deep to cut to overcome these issues.

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.

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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.

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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.

 

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Next steps

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.

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Cap Logs Installed!

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Our cap logs are installed- this means we are almost ready to enter a new phase of construction. It has been a long hard road. Some folks at LHBA claim we are moving at “one gear below breakneck speed” using our lifting poles, but it often doesn’t feel that way…

What are cap logs?

Cap logs are the final logs on the walls. In the photo above, they are the ones that stick way out on the front of the house. Paired with ‘double-butt logs’, they hold up the roof rafters, and give the roof enough overhang to protect the wall logs from rain. In a kit log home, they usually don’t stick out much, but for a butt & pass log home – with an expected lifespan of 350 – 450 years – they are a major part of that lifespan.

Notes on installation

Our plans are for a 40’x40′ cabin. The overhangs on the roof protrude out 7 feet past the walls on the gable ends, and about 4 feet out on the eave side. This means the cap logs have to be 7’+7’+40′ = 54′ long. Also, they need to hold up the roof rafters, so my goal was to make sure they were 12 inches minimum on both ends. With our tapered logs – this meant that the butt end would have to be absolutely huge to ensure at least 12 inches at the tip. This would also throw off our level layers (all 4 corners should be the same height).

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The solution I came up with was to take two normal sized logs, splice them together and put them up as one log together, and let the butts hang out over the ends.

Easier said than done. How do you lift half of a log when the lifting poles are in the corners? In other words, how do you hold up a log in the middle of the house where there are no lifting poles? Easy (not easy)- you chain both together and lift them at the same time.

Although I could have (maybe) installed a temporary center lifting pole- this would take a lot of energy and time- I would basically need a 30′ lifting pole (the size of an RPSL) installed. It would need to be chained to the wall, along with pulleys, etc. Lots of work for something I would use once. So I decided to try everything else before this idea.

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Using a cradle (suggested by Plumb Level), we were able to “safely” hold the logs in place while we pinned them. I won’t go into the details (unless someone is dying to know), but there were a lot of scary moments- like once I got the chained logs in place, I had to remove the unused portion of each log- this involves cutting the excess of the log, and hoping the desired portion just falls into place, with no way to chain it or support it until it was in place. The cradle helped a lot, but there were no guarantees.

Some unlucky (and funny) events from Course 13

First there was the “pinned boot” incident:

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There was a gap in the log I was working on. I was perched up on top pinning it into place, and my boot happened to be placed right where the pin was coming through. Once they go in, they don’t come out. It didn’t pinch my foot- just the edge of the boot- and tight enough that I couldn’t get my foot out. I was stuck. I called for Julie’s help. Now she is not normally one to climb ladders of any size, but she courageously started to climb. She was clinging to the ladder like she was a thousand feet off the ground. I kept encouraging her and she finally climbed up high enough to hand me my crowbar, and I was able to loosen the pin just enough to free my boot. LHBA folks suggested I just leave it there and chink around it, ha ha! ……No.

We had this log that was the right dimensions, but had a nasty hook in it at the tip. No matter how we rotated it, it wouldn’t lay flat. We decided to pin it anyway, and just deal with it later. It ended up being flat most of the way, until about 6′ from the end where it had this big bow in it. Since that corner (NE) has been historically low, we decided having the extra height in the corner would help get the height back up to where it needed to be. But since you can’t accurately measure the height on an odd row, we’d have to wait until layer 14 to find out if it was helping or not. And it is: before the cap logs, our heights worked out great- starting at the NE corner and going clockwise, we have 17’8″, 17’8″, 17’7″, 17’7″. For non-builder types- this means the East and West sides match each other exactly for height, while between the two sides, we are off by 1 inch. Remember- this is all using tapered crooked logs with knots and bends- a real testament to the Butt & Pass method.

And the burned out motor on the drill incident: It is a Black & Decker 1/2″ drill that didn’t really want to drill 300 holes, but it held up for the most part, and then just gave up with the drill bit lodged 12″ down in a log.¬† So I left it stuck up there; “sword in the stone”-like, for the weekend. I figured more power to the idiot who decides to try and steal it. There were no takers.

And five minutes later, the “what the heck happened to the jack hammer” problem: it just lost power in between pounding rebar. I took it home- I guess all the vibration and the weight on the cord from being up so high pulled its guts loose from the switch. I put a new clamp on the wire, taped it in place, and then put the handle back on. Then I taped the cord to the handle on the outside to alleviate some of the stress.

What’s next

The final height of our cap logs determines the final headroom height at the top of the stairs, since they are on the eave side of the house up against the wall. It works out to be (starting at the NE corner and going clockwise): 18′ 4 1/2″, 18’6″, 18′ 5 1/2″, 18′ 4 1/2″. Pretty good.

Now we finish with double-butt logs – these are not logs with 2 butts on them- they are logs that, instead of being normal “butt and pass” logs, are just logs that butt up against their neighbor logs on both ends. In this case, the logs they butt up against are the cap logs.

After that, we begin the next phase: installing the RPSL’s (Ridge Pole Support Logs). Two of these get bolted to the walls. Along with one in the middle. They are 30′ tall, and they hold up the Ridge Pole – which holds up the rafters and the roof.

The Ridge Pole is a monster sweet gum tree from our woods. It is by far the biggest heaviest longest and straightest log I’ve ever cut down. So far, it has evaded me being able to move it. But it won’t for long.

We also need to commit to a height for our girder log. This log spans the width of the house and holds up the 2nd floor. It also ties the East and West wall together so the rafters don’t push the house apart. It provides the “rigidness” that keeps the house tight. At least a little.

I don’t want to think too far, but I’m hoping we can get the roof on this summer.

We had a lovely visit from some LHBA members- Gary (Mosseyme) from East Tennessee came and looked one day in the rain and gave me a lot of good tips, and encouragement. Also, ‘Sdart’ on the LHBA forum- Sara and Rene were very nice and came out to see our progress. They are building in extreme Northern Idaho in an off grid location. They have been to many LHBA homes over the years all over the country and Sara told me, “even after looking at pictures, these homes are always impressive in person.”