Hey Tiny house folks. Zach here with, an update on the house and the hope to disseminate some useful information to those of you who are going down the tiny house road under your own steam. The past two weeks I have been prepping the house to get it ready for the siding install. This is a huge job and there are a lot of little things to do before you can start slapping up siding. In this two-part post I’m going to go over how to prep for and install shiplap siding.
Keeping water out and shedding the water that does get in is the name of the game in a rainscreen wall. Allowing air to flow behind the siding(helping moisture evaporate) is integral to keeping the house dry. To get the air to flow behind the siding, we need to space it away from the house, and give the air room to carry away moisture. This is accomplished through the use of furring strips: thin strips of treated wood installed atop the house wrap. They are placed over the studs so that when we drive the siding fasteners, they make their way to the stud, providing a solid anchor.
Here is a diagram explaining the setup:
You can see the furring strips installed with 2″ coated fasteners over the studs. You don’t need many fasteners for furring, as the screws for the siding will go through the furring and into the stud. There are also furring strips at the edges of the house next to vertical trim. This gives us something to affix the end of each piece of siding to, so that there is no part of it that is loose.
A little gap is left at the bottom and top of each furring strip to allow for a mesh screen. This screen allows airflow behind the wall, while keeping little critters from making their homes on yours.
Here is the mesh screen installed. I wish it was a little cleaner. I found a better way to do this, which I’ll mention a bit later. You can also see the drip cap on top of the bottom trim. This diverts the water over the top of the wall system when it rains. Very important.
Now that the furring is sorted out and installed, it’s time to prep the siding.
Below is the Cypress ship-lap siding that our friend Gary Norton from The Timbershop was so kind to donate to our house. It is reclaimed from an over run and he was kind enough to cut it to our specifications and deliver it to our site. Talk about a sponsor!
To extend the life of the siding, we are coating both sides of it with the Cabot Ausraillian Timber Oil I mentioned a few posts back. We coat the backs and edges of the boards before they go up. It’s quite a chore do to all of the siding like this, but it’s not a step you want to skip. We built these large racks from 2x4s and leaned them up against the side of the shop with tarp over them to keep them dry in the inevitable event of rain.
With the back of the siding sealed, it’s time to begin the installation.
To let the wall breathe from the bottom, we need to leave a gap (I left 5/16ths) between the first piece of siding and the flashing on trim at the bottom. For the first piece of siding we install, it’s very important that it’s perfectly level, as the siding above it will follow the same line it is on. If it is not level and true, all of the siding on the house will come out slightly askew.
Since wood expands when it gets wet, we also need to leave a bit of a gap at the ends of the boards, so that when they expand it will not collide with the vertical trim. Be sure to leave a vertical gap between lateral neighbor boards on the same row to allow for expansion.
It is important to seal the ends of the board where it was cut as you put them up. This is often forgotten, but board ends are the most absorbent part. I like to use extra oil here as they end to soak up more oil than the face of the board.
When it comes to fasteners, I always try to use stainless steel when I can afford it. For siding, I got some special fasteners from Southern Millwork and Supply here in Charleston. I figure I will need about 3,500 fasteners in all for the siding.
I drive the fasteners down through the joint (or rabbet) of the siding. Make sure to set it below the surface of the wood to make sure the next board sits on top of of the one below it with out being distorted by the screw. I put screws in every point that the piece of siding meets the furring strips. Also, for a tight fit, check to make sure that the board is firmly seated on the board below it, so there are no horizontal gaps between the pieces.
After all the fasteners are set, seal the rabbet with oil.
Let’s talk about that screen. It needs to be installed at the top and bottom of the wall and below the windows to allow air to escape from behind the rainscreen. I put along the bottom of the wall in a fashion I wasn’t too pleased about, but knew would work. I have since figured out a little trick to get a nice seal with the screen at the top and bottom of the wall:
Using a 3/8″ dowel, I folded the screen over the dowel and stapled it on the back side, pulling it tight around the dowel at the same time, as a sort of jig. It will form a nice tight tube of screen if you do it right. It acts as a gasket at those gaps, keeping bugs out and letting air and moisture leave the wall.
In the second part of this post I’ll go over installing the screen at the top, sanding and oiling the siding, and other options for protecting the outside of your house. Be sure to chime in with any thoughts or questions.