Basic Stats for Post Frame Home Floor Plans
If there is a single commonality among us humans it is this – we are dimensionally challenged. This situation is even more so crucial when it comes to planning your new post frame home.
Here are a few tips to help you out:
EAVE HEIGHT
Measure from the pressure treated splash plank bottom, to intersection roofing underside at sidewall columns. This is not to be confused with ceiling height (also known as interior clear height).
HOW TO GET AN EIGHT FOOT FINISHED CEILING
For discussion’s sake (and as most post frame homes are concrete slab on grade), set a “zero point” at exterior grade (pressure treated splash plank bottom), slab top will be at +3.5 inches.
To create eight foot finished ceilings requires 8’ 1-1/8” (allows for 5/8” sheetrock on ceilings). This puts us at 8’ 4-5/8”.
Now allow for roof system thickness. With recessed (joist hung between trusses) roof purlins, 6-1/16″ for truss heel height with 2×6 top chord at 4/12 slope (provided you are using closed cell spray foam insulation between purlins). Minimum eave height would then be 8’ 10-11/16”. If using blown-in insulation truss heel height should be insulation R value divided by 3 plus 2″ to allow plenty of eave to ridge air flow above insulation.
What about two floors?
In order to be able to run utilities (e.g. plumbing and ductwork) through second floor supports, I highly recommend prefabricated wood floor trusses. Generally truss depth will be about an inch for every clear span foot with a 12 inch minimum. Adding an arbitrarily chosen 16” deep floor truss and 8’ ceiling on second floor to example in previous paragraph puts eave height at 18’ 4-9/16”.
Stairs challenge even many experienced builders. Finished width must be no less than three feet (if planning allows, four feet is so much nicer), allow for drywall on each side when determining interior framing of stair opening width. In most jurisdictions maximum tread rise is 7-3/4” and minimum run is 10”. In above example, second floor top is 9’ 5-7/8”, so stairs would need at least 14 treads, taking up at least 140” (11’ 8”) horizontally. At stair top and bottom a space, in travel direction, equal to stair width must be provided. Headroom along every point of finished stairs must be no less than 6’8”.
ALLOW FOR WALL THICKNESS
Different providers measure their building footprints differently – some use wall girt outside at ‘call out’ while others use column outside and are three inches greater in width and length, this will need to be accounted for in room dimensions.
Exterior walls with bookshelf girts will be wall column thickness plus 1-1/2” for girts protruding outside of columns. With 3 or 4 ply 2×6 glulams or 6×6 columns allow 7-1/4” plus interior sheetrock thickness. Interior 2×4 walls with ½” sheetrock on each side end up 4-1/2” thick.
APPROPRIATELY SIZE SPACES
Below are popular post frame home rooms and their average square footage, in three categories (listed as small/medium/large):
Entry Foyer (65/89/138)
Kitchen (193/275/423)
Walk-In Kitchen Pantry (17/31/51)
Great Room (487/481/680)
Dining (148/196/281)
Living (256/319/393)
Family (311/355/503)
Recreation (216/384/540)
Entertainment/Media (140/192/280)
Master Bedroom (231/271/411)
Master Bathroom (115/144/210)
Secondary Bedrooms (130/139/178)
Other Bathrooms (93/146/313)
Laundry (67/87/145)
Utility/Mud Room (30/48/80)
Always allow adequate space for hallways (same minimum width rules apply as stairs).
“Justine, pardon me for being confused but: If the tops of glulam posts were manufactured that way to allow cutting, why are they not all that way? There is no rhyme or reason to them. Some of them are laminated all the way to the end and some of them are not. Some of them have one board not laminated in the 3 ply and some have no lamination between the any of the boards on the end. 
We opted to special order our columns – having them manufactured only from high strength 2400f msr lumber. (For some extended reading on msr lumber, please see 
Most often steel truss post frame kits are being sold as ‘roof only’ structures – in order to drive prices down. I have seen some great prices advertised, however as prices get lower, so does usually quality and or service. Things tend to be not included, such as trims and condensation controls. Most of these buildings are not engineered, other than maybe trusses. However, even your best steel truss engineering is negated if quality controls are not present at wherever they are being manufactured. Use of steel of a lesser grade or thickness than specified can compromise strength. Pre-manufactured trusses are supposed to have in plant quality control and random quarterly third-party inspections, having spoken with a few of these (in hopes to find a reliable provider of steel trusses) – none of them appear to be aware of this requirement. Steel trusses should also be fabricated by certified welders. While I am sure there are some great steel truss providers, they are seemingly difficult to find.
My recommendation would be to use wood trusses. If you are trying to gain interior clear height, wood trusses can closely mimic what steel will do. Wood trusses are far easier to finish overhangs and if you want to have a ceiling finished at bottom chord height, wood trusses make it very easy to achieve. Wood trusses are subject to extremely stringent quality control standards. Every set of trusses we manufacture has to have extensive records kept to verify accuracy of members and connectors, plus – we have third party inspections.
DEAR RON: Only articles I have read in regards to possible premature steel degradation have been on websites selling other types of insulation, so I take them with a block of salt. I have closed cell spray foam in my own post frame barndominium and we used it when we added onto our warehouse, can’t say we have experienced any negative challenges. We have also had hundreds of clients successfully use closed cell spray foam applied directly to steel roofing and siding.
Basic Stats for Post-Frame
My first choice would be to design your building to be capable of supporting a ceiling, use raised heel trusses and blow in fiberglass insulation. With raised heel trusses you can get full thickness from wall-to-wall and you do not end up heating dead space between roof trusses. Roof steel should be ordered with a Integral Condensation Control (
Most crawl spaces are created with dirt floors, face it, they are low budget and meet Code with a 6mil black Visqueen Vapor Barrier installed. Now retired Hansen Pole Buildings’ Designer Rick Carr built himself a hunting cabin over a crawl space a year ago and decided to take a slightly different route. He opted to do a thin layer of concrete to cover ground in his crawl space, with an idea of being able to roll around using a mechanic’s creeper, should he need to work on sub-floor utilities. Here is an excerpt from part of Rick’s planning: 
DEAR SHANE: 
Sturdi-Wall Plus brackets are used in a wet set concrete application and provide highest strength bracket to foundation connection when concrete is fully cured. SWP brackets require less concrete coverage than Sturdi-Wall brackets, allowing them to work well in pier foundations, post repair, and renovations. #4 rebar is used in all Sturdi-Wall Plus brackets, except SWP 8 Series where #5 rebar is used. Sturdi-Wall Plus brackets are available in Standard, OT and GL models.
As pole buildings have gravitated from the farms of the 1950’s into the mainstream of popular construction, their owners have been looking for more appeal than what was offered by the average tractor shed.
