I’ve been building small barns and loafing sheds with four inch C purlins oriented horizontally instead of vertically for about ten years now.
My reasons for framing like this instead of the conventional way of welding the purlins vertically to the posts involve simplicity of construction and adding strength to the structure.
With the purlins welded to the face of the pipe the strength of the purlin duplicates the strength provided by the metal sheeting. The purlin and the sheeting are weaker inside-outside than they are up and down in this configuration. So when we orient the purlin horizontally we make the wall much stronger inside outside.
We also provide a place to attach material to finish out the interior of the shed or barn. I can’t emphasize the importance of interior finish out in a horse stall enough. The worst possible thing that can happen in a horse stall is for the horse to kick or paw through metal siding. When they pull their leg back in invariably they cut it so severely they have to be put down.
Since I’m a weldor fabricating a building this way was easy. I would set my posts and then measure center to center spacing for drilling my purlins. I would then drill the purlins with a two and a half inch hole saw. I would slide purlins down the posts and weld them into place.
The four inch wall means that if a room is be insulated the rolls of pink stuff works great and is available anywhere. It also means doors can be purchased at the local lumber yard and then put in the same way a door is put in a stick framed building. There’s no need to pay three times as much for a door frame that can be welded in when a standard pre-hung door can be installed.
Here are some pictures of finishing out a tack room with the pipe and horizontal purlin framing. This building was built with the connector system we’re trying to patent. But it can be built the same way without the connectors if you can cut in and weld.
