Friday, September 26, 2014

Trim and Ventilation 1

Before I can install the metal roofing on the JayBee, I have to install the trim that attaches to the rafter tails all around the outside of the roof. The metal drip edge will get installed over the trim and the edge of the roof sheathing before the roofing goes down on the roof. Once this trim gets installed, access to everything between the rafter tails, the trim, and the roof overhang will be extremely restricted. Therefore, I realized I had a number of things to do before installing this outer trim: stain the rafter bays, install trim up against the walls between the rafter tails, and install air vents that will help air pass along the under side of the roof sheathing and ventilate up at the vent above the ridge board.

The gable ends of the house don't need air vents installed, so these are the easier sides to do, First, I cut trim boards to fit between the rafter tails. I decided to use pine for this inner trim. It is a lot cheaper than cedar, and it won't really be exposed to much weather (since it will be protected by the rafter bays). After the trim boards are cut, I stain them.

Underneath each trim board, I install a piece of radiant barrier. The radiant barrier will reflect heat back into the house (or back out when it is hot outside); it will add R-value to the insulation I will install in the walls. The radiant barrier is a layer of perforated foil that is backed by paper. It is perforated so air can pass through it. I don't want it to be a vapor barrier, since that will be installed on the inside of the walls.

After staining the rafter bay, I install the radiant barrier--paper side facing out. I put a bead of transparent caulk down the sides of the rafters before setting the trim board in place.

Two inner trim boards installed on the west end...

Then four...

Then all six inner trim boards installed.

For the outer trim, I purchased cedar boards. Very expensive, but it will hold up to the weather abuse so much better. It is beautiful, fun to work with, and it smells great too!

Using the cedar, I installed a key block on the end of the ridge board...

and then installed the outer trim boards. The west end is done!

The inner trim along the south and north walls is more complicated because air vents are installed in these rafter bays. Cutting the holes for the air vents in the trim boards is not difficult, but cutting the matching holes in the blocks between the rafters is really hard. The slope of the roof and the top plate of the wall get in the way and severely restrict maneuverability. I have tried using two different hole saws, a jig saw, various drills, hand saws, and chisels.

The air vents I purchased are two inches in diameter and have insect netting in them.  They are white, so I am painting them a cedar color to help them blend with the trim better. Here are less than half of them after they've been painted.

I just purchased a new/different hole saw, so hopefully cutting the holes in the rafter blocks will go more quickly moving forward. I have something like 68 of these air vents to install!

After I cut the inner trim board to fit a bay, I cut vent holes in it and stain it. I cut matching vent holes in the rafter block. I stain the bay, install the radiant barrier and caulk, and then install the trim board.

Finally, I install the air vents, which fit tightly in the holes with friction.

Thankfully, the weather has been great. I just keep plodding along.

Also see:
Trim and Ventilation 2
Trim and Ventilation 3
Trim and Ventilation 4
Trim and Ventilation 5

And, for your entertainment, check out this huge dragonfly!

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