Tag Archives: wet set bracket

Perma-Columns, Posts, Trusses and Purlins, and Mono Truss Roof Venting

This week the Pole Barn Guru answers reader questions about the value of Perma-Columns, setting of posts, trusses and purlins, and the proper way to vent a mono-truss lean-to roof.

DEAR POLE BARN GURU: Are perma columns worth it? JOHN in TRUMANSBURG

DEAR JOHN: When I built my own 8000 square foot finished post-frame barndominium, I could have used any option for columns – mine are directly embedded UC-4B treated glulams. Although this article is over seven years old, it is still relevant to your question: https://www.hansenpolebuildings.com/2018/04/perma-column-price-advantage/

 

DEAR POLE BARN GURU: I’m planning a pole barn pavilion, and would like to have posts set at 10′ on center, and trusses at 5′ on center. Are 2×4 purlins laid flat sufficient (24″ spacing)? Or should they be on edge or upped to 2×6? Standard gable truss, 4/12 slope and 29 gauge metal. Thank you in advance for insight. BRETT in JOHNSON CITY

DEAR BRETT: In my humble opinion, you are looking at doing it in a much more difficult fashion than needed. Set glulaminated columns every 10′ (you could easily do wider spacing to reduce number of holes to dig, columns to set, etc). Align prefabricated wood trusses to match columns – single on each end, two-ply on interiors, with trusses notched into columns. This will eliminate need for truss carriers and greatly minimizes amount of truss bracing required (and usually reduces truss costs). Truss carriers are often under designed and rarely adequately connected to properly resist gravitational and wind uplift loads. Use 2×6 2400f MSR (Machine Stress Rated) purlins, joist hung on edge between trusses.

 

DEAR POLE BARN GURU: Hello, thank you for educating us on best practices. What is the proper way to vent a mono truss lean-on roof? Overhangs will have vented soffit and the rake is currently planned for unvented soffit. I am thinking of installing vented soffit in upper part of rake where the mono truss meets the side wall of the higher structure wall. I have enclosed a picture for reference. TIA NIKO

DEAR NIKO: Thank you for your kind words. Here is a sketch for you (rafter/truss being interchangeable):

Roof steel needs to be long enough to make it to high side of vented closures. You do not want to place vented soffit in rakes.

Strange Claims of Entry Doors Moving

Strange Claims of Entry Doors Moving

When it comes to post frame (pole) buildings and barndominiums, stories being shared often sound like they originated in Twilight Zone episodes.

Reader STEVE in MERCER writes:

“Everyone I talk to recommends one side of the man door be a structural post but there is a 50/50 disagreement on the other side. Some say you need another full length post from the trusses down while others say it’s best to use 4×6’s only up to the top of the door. Some of them state they have seen doors shift and no longer open or close correctly on buildings with the 2 full length posts and haven’t had this happen with the shorter 4×6’s. It sounds like a strange claim so I am wondering if there is any truth to it and is one way better than the other or are they both equally acceptable? Any help you can provide will be greatly appreciated.”

Mike the Pole Barn Guru responds:

In an ideal world, I suppose one side of an entry door should be secured to a roof supporting column. Until just a few years ago, we did not give clients a choice but to do so.

In reality, entry door locations seem to have a mind of their own(ers), as far as where they get placed. There is actually no structural reason to run columns on each side of entry doors up to your building’s roof line provided:

Columns are adequately embedded or wet set bracket mounted to avoid ground line movement;

Column tops are effectively secured to a header able to transfer loads from door posts to roof supporting columns. In most cases, this header will need to be a bookshelf style girt, rather than externally mounted.

Doors should only shift if the site has not been properly prepared to avoid heaving due to frost or expansive soils. Any clays should be excavated from site and replaced with properly well compacted materials. Finish grade should slope away from building for eight to 10 feet at a 5% or greater slope. Downspouts from gutters should discharge 10 feet from the building perimeter or into appropriate drain lines diverting runoff well past the low side of the building. Any underground water flow should be channeled into French drains. 

Basically keep the fill underneath the building area dry (or in expansive soils – at a constant moisture level).

With new 2021 Building Codes being adopted, egress doorways will be required to be frost protected – this being best done with use of rigid polyiso board below grade.