Last Minute Overhang

My original plan had the entire roof system (plywood-rigid insulation-OSB) overhanging the front door.  The rigid sandwiched between the two sheets would have created a strong structural element that could overhang 30" without support.

But, a while ago I changed my design, which I'm now realizing effects this overhang.  Basically, I wanted to create a continuous vapour barrier from the tar paper on the roof (the first layer of sheathing, under the rigid) to the tyvek on the walls.  I also wanted the rigid on the roof to meet the rigid on the wall with no wood in-between.  Doing this left only the top layer of the roof system (5/8" OSB) as my overhang.  Obviously this is no longer self-supporting up to 30" like the original plan was.   I need to spend tonight coming up with a solution!

It's getting dark earlier, so instead of hanging out in the cold and dark at the build site, I went into town and had a nice meal, where I could think things through in comfort.

My plan now is to build triangular supports above the front door to support the overhang.  My decision to build the supports outboard of the rigid is somewhat controversial, but I am going to give it a try.  I am trusting that the rigid insulation will not compress under the weight of the overhang.  Time will tell!

Rigid Insulation Continues

The weather has not been cooperating, and we've had a few setbacks.  It seems to be taking forever to get the roof finished!  Today we put on the third layer of rigid on the roof, and started the rigid on the walls.  The goal was to have at least the top part of the walls down, so that I can spray foam any gap between the roof and wall insulation, in preparation for the final layer of roof sheathing that will be the nailing surface for the shingles.

Action shot!

 Cutting the right angle.

Adding low expansion spray foam to the gap between the wall and roof insulation.  

What was that about low expansion?  Ugh.  As the foam expanded it pushed the wall insulation out, creating a bit of a curve at the top of the wall.  (And, I can only assume, an air gap between the insulation and the wall sheathing.  Not good.)

I had minimal strapping on the walls, just enough to hold the insulation in place.  In future I would recommend having vertical strapping that extends up the wall to the roof, and if possible, attaches to the ends of the roof strapping.  Anything to keep the rigid insulation from bending from the pressure of the spray foam.

The purpose of the flashing and insect screening is to keep critters out of my insulation and out of the air space behind the sheathing.  Here's a detail of how I added insect screening to the bottom of my wall insulation.  First I nailed flashing to the wall, then taped the insect screening to the top of the flashing, allowing the excess to hang down while the rigid is installed...

When I'm ready to put the strapping on I will fold the insect screening up... what this photo doesn't show is that it will be folded over the strapping.  (The strapping will be between the rigid insulation and the screening) This will create a barrier so no critters can get into the wall, while still allowing rain to drain and air to flow behind the siding.

New neighours

I decided to go for a walk to take some photos of the fall colours...

Half the leaves have fallen, but it's still pretty!

But then I came across some distressing ribbons in the trees...

...and this survey marker in the ground.

Every now and then I hear chainsaws, and rumours about a company building rental cottages on the neighbouring lot...so this is a bad a sign that our neighbours are going to be building soon.

I'm not sure how close to the property line they intend to build, but there are no doubts that our private little cove is going to see some big changes in the coming years.

Rigid on the Roof

Keeping with my plan to wrap the entire house in rigid foam, here I am in the process of adding rigid insulation to the roof.  In the end I will have 6" of EPS rigid foam sandwiched between the plywood sheathing/ceiling below and the OSB nailing surface for shingles above.

 

The walls will have 2" of foam, that will extend up to cover the ends of the roof insulation, creating a continuous thermal barrier.  I suspect there will be gaps due to the bumpy installation of the BlueSkin, so I will likely fill the gap between the foam panels with spray foam, and tape all seams.

The rigid insulation has grooves for strapping, which I am alternating to form a grid pattern.  This offsets the joints of the foam panels, hopefully eliminating any three dimensional airflow networks.

I switched from my workboots to running shoes because of the damage I was inflicting on the foam.  I tried to keep my weight on the strapping, but my clumsiness did some damage to the foam in places.  Once piece blew off the roof before I had a chance to fasten it down, and the corner broke off.  I simply glued it back together with some foam adhesive and taped the seam.  Good as new!  *fingers crossed*
 

 

At the peak I used foam adhesive to attach the two pieces, then taped the seam on every layer.  It's important that any warm, moist air from inside cannot find it's way through the roof system.  If it were to find a path to the exterior OSB it would quickly condense on the cold surface and the OSB would begin to rot.

I've made some choices here that some may find controversial.  For one, I have no true vapour barrier on the warm side of my roof.  I have consciously made my roof breathable.  The plywood, tar paper, EPS foam and OSB are all vapour permeable to some degree, which means that if moisture gets in, it can find it's way out again.  Together as a system they act as a very good vapour retarder, which will slow the passage of any moisture through the system, and if I've put it all together well it should ensure that any moist air has time to dry and no warm air has a chance to condense on any cold surfaces.

The main reason I chose not to put a vapour barrier on the inside of my roof system is so I have the option of adding insulation to the cavaties between the rafters at a later date.  If I decide to do this, I will add a vapour barrier at that time.  But the last thing I wanted was to have a roof system with two vapour barriers that could trap moisture in the roof and cause rot.

I call this blog an "experiment" for a reason!  :)

Dragonfly

Friendly dragonfly becomes a living barette!  For a few seconds anyway...

Fall Colours

Dad and I started adding the rigid insulation to the roof today.  The insulation I chose has grooves for embedded strapping to make installation a snap.  However, the challenge was to find the rafters!  I was fastening through the 2" of rigid, 3/4" plywood, and into the roof rafters.  It was a slow process because I didn't want to miss and end up with a screw or nail poking through the ceiling.  This wouldn't be an issue if the ceiling wasn't exposed, but since I'll be seeing the bottom of my roof sheathing I needed to be extra careful.  Luckily we had mom inside keeping an eye on things!  :)

Long story short, I was too preoccupied to take photos... so here are a couple of the gorgeous fall colours!

We only got one layer finished, so there will be more insulation to come.  I promise to take photos next time!

Ceiling Up! Rain out!

First thing I noticed when I arrived this weekend, after three days of wind and rain.... the tarp was completely OFF the tiny house!  The wind must have blown it off, so yet again my tiny house was wet, wet, wet!  Luckily, this weekend I came prepared to get the roof on and the whole place weather tight!

Here is Dad helping with the plywood.  Yup, that's plywood being placed over the rafters!  I wanted to look of boards but the air-tightness and shear resistance of plwood.  I'll add a post to show how I made it happen.

This is me up on the roof screwing in the plywood.  Dad and Mike did the heavy lifting to get the plywood up there.  :)

Then comes the tar paper.  SO happy that rain will no longer be getting into my tiny house!  Hopefully it will have a chance to fully dry out!

Tar paper finished!

Feeling quite cozy inside, with the ceiling done:

I'm so pleased with how the plywood turned out!  And the colour of the rafters contrasts nicely.

View towards the front door from the loft:

Took quite a while to finish the tyvek... one tall ladder made for a slow day of moving the ladder 4 feet, stapling the tyvek, then moving the ladder another 4 feet.  Even with me up on the roof, it still took ages.  I recommend two ladders, so one person can pass the tyvek to the next, who can work while the first person moves their ladder... leapfrog fashion!

Tyvek is on, and taped at the seams. At the top the tar paper folds over the tyvek, and is then coverd with BlueSkin to ensure a completely watertight connection between the roof and the walls.

Bring on the hurricanes!  :)