Tag Archives: moisture control

Attic Ventilation, Shearwall Stitch Screws, and Adding Sheathing

This week the Pole Barn Guru addresses reader questions about ventilation needed for a new attic with metal ceiling and blown-in insulation, a confirmation for endwall needing stitch screws for shear, and if adding sheathing to an existing pole building would add value.

DEAR POLE BARN GURU: I bought a house with a pole barn that is unfinished inside. The metal walls were not wrapped and the only insulation in the barn whatsoever is double bubble on the underside of the barn roof. I am going to have a metal ceiling put in and then blown fiberglass insulation for an R30 value in what will then be the attic. There is currently no ridge vent nor gable vents either so I am concerned about air flow in the attic once the metal ceiling and blown insulation are complete. The eaves have perforated soffit so I’m hoping even after the blown insulation is done that will provide an air flow into the attic. So am I correct to think that I need to have gable vents put at each end or a ridge vent so that there is positive air flow through the attic? Thanks! BILL in STEVENSVILLE

DEAR BILL: Your thinking is absolutely correct – you need an adequate ventilation exhaust point. Ideally, this would be at your ridge. Gable vents, while meeting code requirements, actually only provide good ventilation immediately closest to vent locations.

This article covers requirements for attic ventilation: https://www.hansenpolebuildings.com/2023/06/274512/

In Queen Anne’s County – you are in Climate Zone 4A. 2021’s IECC (International Energy Conservation Code) specifies R-60 for ceilings in your climate zone. As so much of your cost of blown insulation is having installers show up, you may want to consider going with a greater R value than originally planned. Energy costs are not ever going to go down (nor cost of insulating).


DEAR POLE BARN GURU: I have a rear end wall that is labeled shear wall that says I need an inch and a quarter number 12. Stitch screw 9 and 3/8 on center. Is that every 9 and 3/8 on center vertically on each overlap? DAMINA in TONOPAH

DEAR DAMIAN: You are correct. Panels stitched together have roughly twice as much shear capacity as do unstitched panels.


DEAR POLE BARN GURU: Question for you Guru! I bought a property with a small pole building/shed. Is there any value in adding sheathing? If so, how do you retroactively figure out if the roof will handle the additional load? JESSE

DEAR JESSE: If the roof steel is properly fastened (1-1/2″ screws in flats along one side of each high rib in field, #12 or #14 x 1-1/2″ screws both sides of each high rib at eave and ridge) chances are it will perform admirably without any sheathing. Think of steel roofing and siding as acting like very strong, very thin OSB or plywood.


Pole Barn Pricing, Idaho, and a Pole Barn Addition Moisture

This week the Pole Barn Guru pricing of a pole barn with a link to a full blog regarding costs of various sizes, whether or not Hansen Buildings ships kits to Idaho- YES! and moisture control on a new post frame addition.

DEAR POLE BARN GURU: Quick question 30′ x 40/50′ x 14′ high Garage. Pole. Idea what the price is, average?? Just to know if I am in the ball park. Is that installed?? Thank you. GUILLERMO in WATREN

DEAR GUILLERMO: This pricing guide should at least give you a baseline as to where to begin: https://www.hansenpolebuildings.com/pole-barn-prices/

DEAR POLE BARN GURU: Do you ship kits to Idaho? JORDAN in COUNCIL

DEAR JORDAN: We have provided multiple fully engineered post-frame buildings to every state, including Alaska and Hawaii. This would include well over a hundred to our clients in Idaho.


DEAR POLE BARN GURU: Hello! Pertaining to pole barn construction. I am adding onto my existing pole barn, which will be insulated with 7/16″ OSB finished on the inside with wood heat. My question is on a pole barn roof does the moisture vapor wrap go between the metal and the truss perlons? Or between the insulation and inside OSB? Whatever the recommendation is, would your answer be the same for the walls? Thanks. GREG in WEST HARRISON

DEAR GREG: Sounds like you are creating a dead attic space. You should order roof steel with a Integral Condensation Control (https://www.hansenpolebuildings.com/2020/09/integral-condensation-control-2/) factory applied. Order trusses with raised heels so you can have full depth of insulation from wall-to-wall. Vent eaves and ridge in correct proportions. For your walls, use a well-sealed weather resistant barrier (Tyvek or similar) between girts and siding. Rockwool batts between bookshelf wall girts, interior vapor barrier (6mil clear Visqueen works), then your interior finish.

Condensation Challenge, Adding a Garage Door, and Barn Movers

This week the Pole Barn Guru answers reader questions about likely condensation challenges with a closed envelope in coastal South Carolina, an addition of a 16′ wide garage door to an existing building, and if the Guru knows any pole barn movers in central Illinois.

DEAR POLE BARN GURU: I want to keep my building a closed envelope, for conditioned attic space. 40x60x12. My plan is to use closed cell foam 2″ on walls and 3″ on roof deck applying directly to the metal. Do you foresee any moisture issues? Environment is coastal South Carolina, Georgetown county. Hot and humid, very rare to see sub-freezing temps. Also what kind of HVAC do you recommend? RON in GEORGETOWN

DEAR RON: Unless you are going to mechanically dehumidify, expect to see condensation challenges.

Your site is in Climate Zone 3A, where the 2021 IECC (International Energy Conservation Code) specifies minimums as R-15 continuous for walls and R-49 for ceilings. You could achieve this by just over 2″ of closed cell on your walls, however you would need to add another R-28 to your roof. This could be done by adding unfaced Rockwool (Rockwool is not affected by moisture) batts between roof purlins. Specify 2×10 roof purlins 24 inches on center, then use just over 2-1/2″ of closed cell plus 23″ wide x 7-1/4″ Rockwool batts.

Your HVAC provider can recommend a system most practical for keeping humidity at manageable levels.


DEAR POLE BARN GURU: Can you add a 16 ft wide garage door to an existing pole barn? It would be on a gable end of a 30×50 building. ALEC in TOLEDO

DEAR ALEC: Probably, however it should only be done with a structural review from a Registered Professional Engineer as you would be dramatically reducing shear capacity of your endwall.


DEAR POLE BARN GURU: Do you know any pole barn movers in central Illinois? Have a 52×100 we would like to move about 15 miles, ambitious I am sure. MELANNE in DAWSON

DEAR MELANNE: If I had to take an educated guess, I would say it will cost more to move that it would to build new from scratch. At 52′ feet wide, it would take every road being at least four wide lanes between start and end of trip. You can Google “house movers near me” to see if there is anyone in your area.

Moisture Control, Insulating Existing Structure, and a Post Rot Fix

Today the Pole Barn Guru answers reader questions about moisture control, insulating a building with a ridge vent, and a solution for replacing posts that have rotted out.

DEAR POLE BARN GURU: Thanks for the abundance of technical information you provide your readers. Like many of them, I inherited a pole barn with the same ceiling sweating, heat, cold issues and need a post construction solution. The slab sweats only in some places. I have a typical wood post with 2×4 horizontal purlins, wood truss and purlin roof, and metal skin walls and roof. My goals are, #1 stop the moisture inside, #2 insulate for moderate comfort (no codes to comply with and I can heat with a wood stove and abundance of wood) , and #3 if I can afford it, skin the walls with T-111 or other wood for an attractive look inside. I did not see any suggestions about double-faced radiant barriers in your other articles. Do you think expanded polystyrene cut to fit in the 1.5 inch cavities to flush with purlins, and then add the radiant barrier (bubble type) stapled over that directly to purlins would be appropriate and not trap moisture? If so, should I allow and air space between the polystyrene and radiant barrier? Many thanks, Mr. Retired…finally! JOHN in CHEROKEE VILLAGE

DEAR JOHN: Thank you for your kind words. If your slab sweats at all, it is likely there is no vapor barrier under it and it would behoove you to apply a sealant. 1.5″ expanded polystyrene (EPS) boards cut to fit tightly and with all seams tightly sealed would give you some degree of insulation (roughly R-7.5 other than at girt and purlin locations). You could add unfaced rock wool batts to increase insulation. Radiant barriers provide next to no insulation value and only function if seams can be perfectly sealed, we’ve actually opted to no longer offer them to our clients.

Unless you want to heat area in triangle of trusses, you may want to consider insulating at ceiling level, then vent dead attic space above.


DEAR POLE BARN GURU: Hello Mike. I came across your website while trying to learn more about what to do with the ridge vents in a pole barn when you plan on insulating it with closed cell foam. My wife and I purchased a property that has a 36w x 48L unconditioned pole barn with 8 skylights, a couple of ridge vents and (2) sets of huge doors on each end. While we know this will never be a tight building, we need to insulate it for our pets (10) dogs and (11) cats, and for a hangout area for us to spend time with them rather than inside our home.

We have a high-end American Standard heat pump split system that will condition the entire space.

Would you be able to give me any advice on what you recommend I do regarding the existing ridge vents? I’m not sure if I should insulate around them and leave them as they are…open. Or, should I temporarily trim out around them and seal them for the time being?

Any information you could provide me on this topic would be greatly appreciated. ROGER in HOUSTON

DEAR ROGER: With those large sliding doors, your investing in closed cell spray foam may be for naught. If your expectation is to be able to control any sort of heat loss/gain you should consider replacing them with insulated steel sectional overhead doors.

On to your question – seal off ridge vents and spray foam across skylights (or, even better) replace them with steel roofing before insulating.


DEAR POLE BARN GURU: What are my options on repairing 32×40 all 6×6 posts are rotted off ground level. Floating slab, perma colum, helical peir, or strongway sleeve. CHAD in GREAT BEND

DEAR CHAD: I would repair one column at a time. Temporarily support roof system being supported by a column. Cut column off above point of decay. Excavate embedded portion of column and remove – hole being dug to be at least below frost line. Insure bottom of hole is firmly compacted. Place a sonotube in hole, attach an ICC approved wet set bracket to bottom of column and backfill with premix concrete. Compact granulated fill around sonotube in six inch lifts. Repeat at each column.