Tag Archives: condensation under roof steel

Issues with Condensation, Ground Water, and Overhead Door Size

Today the Pole Barn Guru answers questions about, condensation, ground Water, and an overhead door size.

DEAR POLE BARN GURU: Good morning,

My name is Brett and about to complete my Hansen Pole building.

I have having issues with condensation from my metal roof given the recent freezing weather. I do have a vapor barrier, but is not stopping the condensation that is now dripping into insulation and drywall.

Can you help me with this? Need a resolution quick

Thank you



DEAR BRETT: Your building’s dead attic space lacks adequate ventilation. You need to replace closed cell foam closures currently under ridge cap with Vented ones. Cut out any radiant reflective barrier between ridge purlins. Make sure to have an inch or more of free flowing air above insulation closest to sidewalls, so as not to impede air intake from building’s vented soffits..


DEAR POLE BARN GURU: Does it make sense to build a pole barn on standard frost walls where ground water and subsequent frost heaves are a problem? JOHN in LANESBORO

DEAR JOHN: Ground water is going to be an issue no matter what you do. Frost walls are going to be very costly (https://www.hansenpolebuildings.com/2018/11/foundations-2/), and you’d have to find a way to keep water out of your excavations long enough to set up forms and pour.

I’d be wanting to build up grade at building site for any type of construction.

For further reading – https://www.hansenpolebuildings.com/2013/11/sonotube/ and https://www.hansenpolebuildings.com/2011/11/site-preparation/.


DEAR POLE BARN GURU: Can I install an 18 ft wide garage door in a 20 ft wide pole barn? WILLIAM in TOWNSEND

DEAR WILLIAM: With proper structural design, probably. There are some downsides of this application, however. You will be extremely limited in your ability to place anything along building sidewalls. Care will need to be given in opening vehicle doors so as not to smash them against each other, or sidewalls.

For an 18 foot wide sectional overhead door, I normally recommend a building width of no less than 24 feet.


Condensation Under Roof Steel

Condensation Even With Radiant Barrier Installed Under Roof Steel

It seems every winter I get a few messages similar to this, So far, this winter, I have gotten two, both from newly constructed post frame buildings and from the same area of the United States (which is known for high humidity).

Reader SAM in GREENBANK writes:

“Hi there.  I’ve almost completed the building, and It’s been getting cold lately.  I noticed that every time we have a frost I have condensation drips all over inside the barn.  I was under the impression that the foil backed bubble wrap was supposed to prevent this.  Is there something I can do to stop it?   Is this normal?   I’m having to keep all my tools under cover even though they are inside.  Not ideal.”

Mike the Pole Barn Guru Responds:

The radiant reflective barrier does keep warmer moist air from contacting the underside of the colder roof steel and condensing. If it has been below freezing inside your building, and fairly humid, water vapor will freeze to the underside of the barrier as well as the roof framing members. Most often the excess humidity is a product of a relatively freshly poured concrete floor (tremendous amounts of water vapor are expelled from a concrete slab as it cures), a concrete floor which does not have a well sealed vapor barrier beneath it, or (in buildings without a concrete floor) the ground under your building will not freeze and when the ground outside starts to freeze the excess ground moisture rises inside of the building (think of a cork being removed from a bottle).

Possible solutions (may have to be used in combination): heat the building to just above freezing, open the doors to allow excess moisture to escape (especially in cases with a fairly fresh pour or no slab), if no vapor barrier under a slab – seal the surface of the slab to prevent moisture from coming through. Basically it takes a reduction of humidity inside of your building.

In cases where eave and ridge ventilation was not provided for initially, adding gable vents might help to alleviate some of the interior humidity. When I was a builder, we erected a boat storage building over (we found out later) what had been a pit where asphalt waste from old roads had been deposited. Water sat in between the chunks of asphalt – we had basically built over an underground lake!

The only solution was for the owner to install power vents to pull the humidity out of the structure!