Adding a Lean-to on a Pole Barn

In six years and nearly 1500 articles written it is hard for me to believe I have actually overlooked the topic of a lean-to being added to a pole barn!

For the biblical readers amongst you, “Ask, and it shall be given you; seek, and ye shall find” (Matthew 7:7). Well, good reader DANNY in DANA is asking:

“I want to build on a Lean-to on my pole barn and have really having time getting information online, nothing address this project that I’m trying to get started on?”

Mike the Pole Barn writes:

What exactly is a lean-to anyway?

According to the sum of all human knowledge (www.Wikipedia.com) a lean-to is a type of simple structure originally added to an existing building with the rafters “leaning” against another wall.

Wikipedia may consider a lean-to a simple structure, however there is far more involved than may meet the eye. Before diving deep into adding a lean-to to an existing pole barn (post frame building) a competent Registered Design Professional (RDP – engineer or architect) should be engaged to determine the adequacy of the existing structure to support the lean-to. Failure to do so can result in catastrophic failures – causing injury or death.

Before I ramble on further, this article is not an engineering recommendation and should not be considered as such. Please utilize only services which can provide RDP sealed drawings for your project.

Why bother? It is just a simple roof!

Here are just a few considerations:

The footings beneath the existing wall columns need to be verified for adequate diameter to support the weight of the existing building, the lean-to and the weight of imposed climactic loads such as snow.

Even if the newly proposed lean-to is just a roof, the existing wall columns need to be adequately sized to support a greater surface of roof for horizontally acting wind forces. If the lean-to is enclosed on the low eave side, the new lean-to roof outside columns must now carry the wind load against the top half of the new wall plus the entire roof!

A change in roof pitch between the existing building and the lean-to, or the lean-to high side being lower than the existing structure can result in snow drifting and snow slide off loads which need to be carefully considered.

If the existing building has trusses or rafters supported by a truss carrier (header between the trusses) it is unlikely this carrier will be adequate to support rafters being attached to it.

Come back next Tuesday for …the rest of the story on adding a lean-to onto an existing pole building.