I estimate the roof of my log home will weigh around 50,000 lbs. In class, they taught us that you need a girder log that is crosswise to the ridge pole to increase the strength of the structure. The girder log is also known as a collar tie. Its job is to keep the walls from spreading apart due to the weight of the roof, as well as to support the second floor.
Since we used pulleys, we knew we could install the girder log at any time after we reached second floor height. We decided to wait until now.
Height of girder log
I was stuck, though, at how high to set the girder log. Our walls are almost exactly 18 feet high. Minus one foot for the first floor and another foot for the second floor gives us eight feet for each floor. But were we supposed to put the bottom or the top of the girder log at eight feet?
I ended up calling my friend and fellow LHBA member Ivan to see what he thought. He said building code specified 6 feet 8 inches for head space: as in, don’t set the girder log any lower than 6′ 8″ from the finished floor height. That was the perfect starting point. So I added a foot to that for the finished floor height (7′ 8″), and then rounded up to 8′ and placed a mark on the wall at that height. We decided the fat end of the girder log would go over the kitchen, since on that end of the house, the girder log holds up the bedroom areas as well as the bathroom and other rooms. The other end is open to the living area, so it only needs half the joists.
Installing the girder log
Installing the girder log with pulleys is fairly straightforward: get the girder log next to the house, cut a hole in the house, attach a pulley and lift until the log is in or near the hole in the wall. Attach a second pulley through the hole and pull the log into the house. Continue to adjust pulleys and lift / pull until log reaches other side of the house. Level the log, cut another hole, and pull it through. Then pin it with rebar. Make sure it is raining – you don’t want to have too much fun. 🙂
As usual, my wife was a huge help. I pulled on one pulley with the tractor, while she let me tie the other pulley to her car. My daughter watched my hand signals from inside the car and relayed them to her mom. We are at level “pulley ninjas” at this point in the game.
Installing the Girder support log (GSL)
On smaller log homes, an angle bracket can be made to support the girder log. The bracket is bolted to the middle RPSL, and the girder log rests on the bracket. On a 40×40 log home, the span is at least 20 feet between supports, so a girder support log (GSL) is required. The GSL is not hard to find- it only has to be about eight feet long. We pulled it from a scrap log we had, and picked it so it has no knots and very little bow. I dragged it with the tractor (yes, it still weighs about 500 pounds) over to the house, then used the pulleys to drag it inside.
I knew the girder log sagged a bit in the middle by about two inches (because the string level told me so!), so I measured the space between the pier and the girder and added two inches. After doing a test fit, I cut the GSL to the right length, drilled a hole in the bottom for the rebar from the pier, and then lifted it as close as I could to the girder log, which was still sagging. I chained it in place and moved the chain hoist to the girder log and lifted the sag out of it. With the sag out of the girder, I was able to just push the GSL by hand into position. Using my favorite tool (can(t) hook), I rotated the GSL into position, then lowered the girder onto it and drove a pin through the girder to keep it from slipping. Later, I’ll install 1″ all thread and bolt the GSL to the girder. This puppy ain’t going nowhere.
We install the bird blocking, which fills in the space between the rafters and the walls. I’m calling around to get the best deal I can find on 2″ x 6″ tongue and groove car decking (which is the “hardwood floor” you see when looking up at the roof from the inside), but not having much luck finding a good deal. It looks like it will cost me about $7,000 just for this part of the roof. Still need to get the underlayment, the 2×12 sleepers for the built up roof, the insulation, plywood, and shingles or metal roof (if we can afford it). The roof really will be the single most expensive part of this build. On the other hand, I can’t wait to have the whole thing dried in.