The Log house Project begins........

[Rock knocker]

MotorSeven,

You stated that you didn't feel that the moisture was from inside the house, because your vapor barrier shell was very good, and everything was taped up. If that was true, then it would work in reverse, and not allow moisture from outside and above to penetrate it and hit the car decking. That doesn't seem to be the case. The water is either from inside the house, or your shell has failed.

The causes of the water:
1) Internal house moisture condensing against the bottom of the insulated vapor barrier. Caused by a insufficient insulation

2) Internal house moisture leaking thru the vapor barrier and condensing on the sheet metal. It then penetrates the vapor barrier at another spot and invades the car decking

3) Exterior moisture condensing against the underside of the sheet metal, and using the same mechanism as (2).

In all cases your vapor barrier is suspect to some degree, in at least some locations. As such, if you fill the purlin void and ridges with insulation, you are taking the chance that condensate will form on the underside of the sheet metal-spray foam assembly, but above the rigid foam sheets. This condensate will have no where to go but down.

I suggest that you investigate the amount of insulation you have, and you warm-side vapor barrier

 

[ultraglide62]

Motorseven I think you should research Ron's suggestion and web site diagram on pg 178. I just put a metal roof on a small cabin in WA. It gas a tongue and groove fur car ducking roof. I constructed 2x6 inch boxes and filled them with 6 inches of solid core sealed foam and covered them with sheathing and the sticky ice/snow shield. My metal roof with vertical ribs is screwed directly to the sheathing.
This is the way Ron's diagram shows it. I am glad I looked at it because I will now add vents in my cedar facia boards.
I think you need to confirm the proper fix and do it right. Your place is too nice to have to worry about this over the next few years. You need to be able to put this behind you. Good luck.
Ultraglide62

 

[ultraglide62]

I hate auto-correct on smart phones.
Ultraglide62

 

[ultraglide62]

I hate auto-correct on smart phones. Decking not ducking!
Ultraglide62

 

[simonds]

Was the moisture content in the purlins checked before the steel was installed? With all of those purlins, could it be possible that they are still drying out and may get better after a good dry summer season? I think that I would give it a season before doing anything major.

 

[MotorSeven]

Wow, y'all are giving me a lot to study(thanks).

Rock, I'm just throwing ideas and suspicions out there. My vapor barrier could have failed and the ventless could be the culprit. I aim to test that theory as soon as the weather turns colder and I will be able to report back here with a definitive answer either way.

I knew this, but had not considered it...yes there is still a lot of water trapped in the air dried lumber used in the construction of this house. Generally speaking that will take two years to dry out as far as it can.

I do think we all agree on one thing......boost air flow. I have some ideas and will be kicking them around.

Company is here, one Turducken & three turkeys are hopefully thawed out and the frying/baking will begin.........Happy Thanksgiving!!!!!!!!

 

[zing]

A for sure cure would be to add 2x4 to the top of your rafters/trusses and re install on top of that, that way you would have a 3 1/2" air passage from eaves to the top 'vent tunnel (chamber)'.

I don't think vertical purlins alone are an option now that he has already installed the horizontal ones because the screw holes in his tin will no longer line up. Perhaps 1" vertical purlins to allow bottom to top airflow, followed by 1" horizontal purlins to line up with his current screw holes, followed by vapour barrier, followed by the tin again. That is a whole heck of a lot of mucking around though.

I agree that the condensation is not likely coming from internal of the house. Not through the tar paper and the seam taped 3" foam. There are big air spaces between those horizontal purlins that are warming up all day long. Now that the nights are getting colder, faster, the tin is cooling fast and the air trapped in those pockets is dropping it's condensation on the inside edge of the cooled tin before it can switch places with the cooler outside air.

Here's hoping that the ridge vent does the job. :thumbsup:

 

[ben2go]

I too am glad this is coming up now.I have experienced the dreaded tin roof drip.I knew what the problem was and how to solve it.I just didn't know the proper way to do it.I have a question or two about my future set up.Should I ask the question here or start my own thread?

 

[tommu56]

In my garage the builder suggested putting tyvek over the purlins to prevent the condensation.
So far it has worked fine but it is an open structure in side with concrete floor.

tom

 

[tommu56]

In my garage the builder suggested putting tyvek over the purlins to prevent the condensation.
So far it has worked fine but it is an open structure in side with concrete floor.

tom