Adding a Second Floor in an Existing Pole Building
More than one pole (post frame) building owner has an idea of adding a second floor inside their existing building. Or, they plan a new post frame building with an idea of a future second floor being incorporated.
This apparently simple proposition has no simplicity involved.
Reader RYAN in HAMPSTEAD writes:
“Good morning,I have a 30×40 pole building, and I’m looking to add a partial second floor. The posts are 8x8s, set at 8′ OC. I’ve attached a layout for trusses that I received from another vendor, based on specs I provided. The exact indoor measurement is about 29’11” outside to outside of the 8x8s (to the exterior sheeting). The distance between the posts is about 28’6″. So the joists should be field trimmable or around 29’8″ to carry from ledger to ledger. I do not currently have the ledger/ribbon boards purchased or installed.
The trusses will be clear span, and the total floor space will be 30’x24′ with a cutout for a staircase. Can you send a quote for this? The shipping zip is 21074.
Mike the Pole Barn Guru Writes:
Hansen Pole Buildings does not manufacture trusses, so we weren’t able to solve this portion of Ryan’s challenge. However, there are some considerations anyone should consider when looking towards a second floor being inserted in an existing post frame building.
Before moving forward, an EOR (Engineer of Record) should have originally designed your building. This person should be consulted with, as a second floor places a tremendous load upon wall columns and may overload footings (not to mention columns themselves), possibly causing columns to sink. Headers (also known as ledgers/ribbon boards) as well as attachment of floor trusses to them also need to be engineer designed. If somehow an engineer did not design your building, a competent one should be engaged to verify adequacy or design a repair.
Don’t be pennywise and pound foolish when it comes to structural changes involving a second floor, mezzanine or loft – lives you save may be your own, or those of a loved one!
What Size Posts Does My Building Need and How Deep Should They Be?
Reader ANONYMOUS in BENTON writes:
“1. If my building has 16 posts and posts are 12 feet apart do I need 4×6’s or 6×6’s?
2. If the plan shows 16 feet above grade how much do I need underground?
3. If the posts are set 12 feet apart will two 2x12s glued together support a truss system with a total length of 36 feet?”
Mike the Pole Barn Guru responds:
While I appreciate your questions, we as a company and me as an individual do not provide free engineering services. In answer to your questions:
1) Without knowing the full dimensions of your building, including roof slope and overhangs (if any), if the columns will be adequately tied into a concrete floor, as well as your site’s snow load, design wind speed and exposure, seismic zone as well as the dead loads which will be carried by your building there is no possible way for me or any RDP (Registered Design Professional – engineer or architect) to be able to answer this.
2) The depth of the columns into the ground should be shown on your engineered building plans (you do mention you have plans). At a minimum the holes should be no less than 40″ deep and must extend below the frost line. Ultimately the depth and diameter will need to be determined by the RDP in consideration of the factors listed in (1) above, as well as designing for the ability to adequately prevent uplift.
3) Since I would use double trusses which bear directly upon the columns, there would be no need to use any other type of dimensional lumber to provide headers for a truss system. Again, this is where your RDP can design to adequately provide an engineered system to support the trusses.
My best advice, since I am guessing you are somewhat floundering in this, is to invest in a fully engineered post frame building kit package which includes plans sealed by a RDP and designed specifically for your building, at your site. It just isn’t worth trying to avoid the small expense into a proper design – especially when the lives of the occupants depend upon it.
Here are some other articles which pertain directly to this subject and should be read: https://www.hansenpolebuildings.com/2014/12/free-pole-barn-plans/ and https://www.hansenpolebuildings.com/2017/11/dont-engineering-fool/