Vapor Barrier

PDF versionPDF version

Man are we ever getting close to that day.

For those of you who are new here, that day is the day when we have the Momplex full insulated, and it doesn't matter if it's -50 degrees outside, if the wind is blowing 80 MPH, if it's snowing . . . even if it's freezing rain. That day is the day we can work without -100 below boots and three layers of down. That day is the day we can work without gloves, when batteries can charge, and tools still work.

It's going to be a big day for us!

That day also is the day we get to officially start on the interior. Because today, and all the days up to it, even if we have been inside, sure don't feel like we are working inside.

Sponsor Box: 
<script type="text/javascript" src=""></script>
Author Notes: 

Now we can trim off excess.

You just use a utility knife to trim it off, leaving a few inches or so to overlap the walls.

I know this seems like a fairly simple task, but everything is so much harder when you are working over your head on a ladder.  And the Momplex roof is two houses in one - about 2000 square feet.  So it definitely was quite a task getting her done!

With the vapor barrier complete, what does that leave us with?

Yep, we get to hang drywall next!

And after drywall, we will blow in insulation and the Momplex will be fully insulated!  That day is so close!

Step 1 Diagram: 
Step 1: 

We've got the electrical boxes in the ceiling, and all other utilities needed to be run through the ceiling installed. Wires have been run. The ceiling itself has been blocked as needed for hanging drywall. It is FINALLY time to finish off the roof!

Today is vapor barrier day.

Now before I get into this process, know that ever climate and type of building requires different insulating and moisture control. Case in point - our walls are ICF and no vapor barrier is required. So check with your local codes and find out what works in your climate for controlling moisture.

Where we live in Alaska, this is what happens if you don't have a vapor barrier in your ceiling or your vapor barrier is installed improperly:

Moisture builds up inside your house just by living in it (showering or boiling water can put cups of water into your house!). The moist air escapes the house through the ceiling and becomes frost in your attic when it meets -40 below air in the attic. The frost builds up through the winter. When spring comes, the frost melts, and the water saturates your insulation, and drips through your ceiling into your house, creating water damage and mold problems.

Vapor barrier is a good thing!

Step 2 Diagram: 
Step 2 Instructions: 

But here's the problem. When you put the vapor barrier up with staples, the stapled holes create opportunities for the moisture to escape through the ceiling. You can go back and tape the stapled holes, but then when you put drywall up and screw it on, you've got more holes in your vapor barrier.

I know this isn't a huge issue in other climate, but up here where half of the year it's winter, and on a winter day, there can be a 120 degree temperature difference between the inside and outside of your home (yes, it can be 70 degrees inside and -50 outside), you'll start seeing every single screw hole in your ceiling building up frost.

So what we do is put this tar stuff up on the studs in the ceiling.

Step 3 Diagram: 
Step 3 Instructions: 

This stuff never dries. It's like bubble gum that never dries. It is awful stuff. Do not get it on your shoes or in your hair, it will never come out.

Step 4 Diagram: 
Step 4 Instructions: 

The tar stuff gets applied to all the ceiling studs.

Step 5 Diagram: 
Step 5 Instructions: 
And it drips down, creating landmines of tar on the floor. I'm really careful to not let this stuff drip on my hair - having my hair washed in gasoline or the like doesn't sound like a good day at the spa.
Step 6 Diagram: 
Step 6 Instructions: 
For the vapor barrier, we roll it out on the floor.
Step 7 Diagram: 
Step 7 Instructions: 
And cut it to length with a utility knife.
Step 8 Diagram: 
Step 8 Instructions: 
Then the vapor barrier is spread out in the big room.
Step 9 Diagram: 
Step 9 Instructions: 
And brought into the room it will be installed.
Step 10 Diagram: 
Step 10 Instructions: 
Careful not to get tar on it!
Step 11 Diagram: 
Step 11: 
Then you put the vapor barrier over your head.
Step 12 Diagram: 
Step 12: 
Climb up the ladder
Step 13 Diagram: 
Step 13: 
And start stapling it up. You want to pull tight here and do a neat job. We start in one corner and work our way to the other.
Step 14 Diagram: 
Step 14: 
It gets stapled to the studs in the roof, over the tar stuff.
Step 15 Diagram: 
Step 15: 

And then all the way over to the other corner.