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).
DEAR KAL: You are in Climate Zone 5A, so a ceiling vapor barrier is not required by Code. Building scientist and founding principal of Building Science Corporation Joe Lstiburek states, “Plastic vapor barriers should only be installed in vented attics in climates with more than 8,000 heating degree days.” (More on degree days here:
DEAR JONATHAN: We have had several clients provide their own pre-cast Permacolumns and they can be incorporated into our engineered designs. There is, however, a less costly option to explore:
DEAR POLE BARN GURU: Hello, my question, which I can’t seem to find a straight answer anywhere online. Is anything needed between interior PVC panels, closed cell spray foam and the exterior metal siding? The pole barn is located in southern Indiana. It’s used as a shop and being heated occasionally with a wood stove. BENJAMIN in INDIANA
Mike the Pole Barn Guru writes:
DEAR POLE BARN GURU: Once I save up the funds, I plan to have you guys design me a 28′ x 48′ pole barn with 12′ walls and 6/12 roof. Due to various reasons I will be foregoing metal siding and utilizing wood sheathing and siding for the exterior. I know you measure wall height from the bottom of skirt board, but is it possible to have 12′ walls from top of concrete floor to bottom of truss so as to efficiently utilize sheet goods on the interior walls? Also is 12′ post spacing possible? Thanks TROY in HONEOYE FALLS
DEAR JOSHUA: Our fully engineered post frame (pole barn) kits include: Mutli-page full size (24″ x 36″) engineer sealed structural plans, specific to your building, on your site, detailing location and connection of every structural member. Includes foundation design. Engineer sealed calculations to verify adequacy of each member and connection. The industry’s best fully illustrated Construction Manual. Unlimited Technical Support from a team who has actually built post frame buildings. All columns, pressure treated splash planks, wall girts, blocking, headers, jambs, roof trusses (and floor trusses where applicable), truss bracing, roof purlins, joist hangers, specialty connectors for trusses to columns, steel roofing and siding (or alternative claddings), steel trims, UV resistant closures for eaves and ridge, powder coated diaphragm screws to attach steel, doors and windows. In a nut shell – everything you need to successfully erect your own beautiful new building other than concrete, rebar and any nails normally driven from a nail gun.
DEAR TOM: While shear walls (and/or bracing) can make your building shell stiffer, they do not eliminate moment (bending) loads having to be transferred through those brackets and bolt connectors. Your best bets are to either build with columns outside perimeter of existing slab, or cut out squares at each column location for either embedded columns (best design solution) or to pour wet-set brackets into piers.
Rather than having to make your enclosed building portion significantly taller, I would recommend you approach this with an idea of it basically being a 40 foot square building, with one sidewall ‘pulled in’ 10′. If you went with say a 13 foot eave height, you could have 12 feet of interior clear height both inside, as well as under your roof only portion. This will allow for plenty of headroom both inside (where you could have a vehicle lift) and outside for your camper. With a 4:12 roof slope your overall building height would be 19’8″ under this scenario.
DEAR POLE BARN GURU:
DEAR RAYMUNDO:
DEAR RAY: If your building is still under construction (in framed up stage) you should be able to stand in middle of roof and rock building back and forth by several inches, just by shifting your weight. Here is where temporary diagonal bracing of wall columns comes into play (especially if some or all of your building columns are not backfilled with pre-mix concrete.
“I am planning a 45×56 pole barn, with ~16ft deep mezzanine on the end wall. The zoning rules limit the building height to 25 ft. It seems the best options are scissor trusses with 1) 4:12 roof pitch and 2:12 ceiling pitch which puts the eave height around 16ft or 2) a 3:12 roof pitch with ~1:12 interior pitch which puts the eave height around 17.5. With a 9′ 4” Mezz Floor height and a roughly 16inch thick floor, the height under the mezz will be just under 8ft, and the min/max heights above the mezz will be roughly 1) 6 -10′ or 2) 8- 10′. The space below will be used for vehicle storage (or possibly a pool table), and the Mezz will be used as a recreation area in the center with offices on either side wall. The whole building will be insulated and climate controlled.
DEAR POLE BARN GURU:
DEAR POLE BARN GURU:
DEAR SARA: Our oldest daughter Bailey is a highly successful Walking Horse trainer in Shelbyville, Tennessee. She is having a new home constructed currently on acreage and had asked Dad to check out arena prices for her. I priced 60′ x 120′, 70′ x 140′ and 80′ x 160′ buildings, all with identical features. Surprisingly to me, they were all within pennies per square foot of being equal! Being as you are in a more snow sensitive area, I would suspect your pricing curve to have more of a gradual increase as spans increase from 60 feet.

DEAR POLE BARN GURU: Can you do a 48×48 gambrel style pole, 18-20 ft high? PAMELA in CASPER
As an alternative to a five foot elevation drop, a pitch break could be used between main clearspan and lean to roof. I usually try to avoid going steeper-to-flatter as it adds to construction complexity, adds to costs and provides a place for accumulation of debris (tree leaves and needles) as well as snow sliding off the enclosed portion.
DEAR JIM:
DEAR POLE BARN GURU: 
DEAR STEVE: I’d be contacting local installers of closed cell spray foam insulation. You will get close to R-7 per inch of foam (again, must be closed cell) and do not have the ventilation issues posed by using batt insulation between purlins. You will need to block off the eave and ridge vents for this to be an effective solution.
DEAR BRYAN: Indeed, s
If you are planning on climate controlling the building and having a ceiling (smart choices), then the eave height will need to be further increased by the amount of roof truss heel height greater than the most common six inches.
In your neck of the woods (Oregon), the vast majority of post frame (pole) buildings are constructed with a single truss mounted on each side of a sidewall column, with purlins (usually 2×6) run over the top of the trusses. With a 2×6 top chord roof truss and a fairly common 4/12 roof slope, the combination of the trusses and purlins is going to chew up 11-7/8” of space. A nominal four inch thick concrete slab is another 3-1/2” thick. After these two deductions, your 18 inches of distance from top of door opening to eave ends up being all of 2-5/8”clear.



One of the more popular ones is clients who want a 16 foot tall eave height and a loft (either a full or partial second floor).
Case in point – the building in this photo. Looks great, doesn’t it? I am sure the building will function to well meet its designed needs.
A few years ago the ASABE (American Society of Agricultural and Biological Engineers) set out to establish a standard for uniformity in terms used in the design, construction, marketing and regulation of post frame building systems. This document, approved as an American National Standard (ANSI/ASABE S618) in January 2011, provides definitions and classifications associated with post-frame building systems.
Personally, when I get specific unusual requests, I usually try to dig to the root of the request. Asking a question such as, “Do you mind sharing with me why adding or using “X” is important to you?” If you hear this question from me, it is only my wanting you to be a satisfied client. I am not criticizing, just trying to figure out what the “gain” is.