Tag Archives: Rafters

Stretching Stick Frame Construction

Post frame (pole building) construction is popular due to efficiencies of materials (ability to do more with less) and speed of construction.

Reader RAYMOND in BARLING is trying to find a way to make stick framing cheaper, he writes:

“24×64 pole barn in question. 4 pitch.  I am just comparing the cost of alternate designs.

Using 2×6 rafters with purlins across top for metal. Can I part from the standard 24 OC of rafters and expand to 30 OC (since more support from purlins)?

Furthermore, is it possible to use 30 OC studs all around, instead of poles (since more support from purlins on walls)

I would really appreciate your wisdom.

Thanks!!”

Mike the Pole Barn Guru says:

Let’s begin with, “since more support from purlins on walls”. Studs in stick framed walls will not resist wind loads perpendicular to a wall any better due to lateral support from purlins (actually girts) installed horizontally.

Your rafters are also going to be unable to support greater roof loads due to purlins being attached.

Building Codes have prescriptive requirements limiting what can and cannot be done with conventional (stud wall) framing, without having to have a fully engineered building. This would include studs and rafters being no greater than 24 inches on center. They also preclude wall heights of over 12 feet (you did not mention any heights however it should be kept in mind).

International Residential Code (IRC) Table R8702.4.1(1) provides rafter spans for common lumber species with a roof live load of 20 psf (this happens to be Code minimum whether snow is present or not). Being as you are in Arkansas, we will assume the minimum load as well as no ceiling being attached to rafters. With rafters 24 inches on center your rafters would need to be 2×8 #2 Southern Pine at a minimum. You would also need to provide ceiling joists or rafter ties to resist outward push of rafters on bearing walls. In order to get full value from rafters, ratio of rafter ties measured vertically above the top of stud walls to the height of roof ridge would need to be 1/7.5 or less. At a 4/12 slope ridge height would be 55.64″ meaning rafter ties could be located no more than 7-3/8″ above top of stud wall, so plan on then being at least 20 feet in length. A ridge board must also be provided as well as a collar tie, gusset plate or ridge strap (please refer to IRC R802.4.2).

Stud walls also mean you would need to make provisions for structural headers above any opening in any load bearing exterior wall. With post frame construction openings can be placed between columns in exterior walls, eliminating structural headers (this assumes trusses are placed aligned with wall columns with roof purlins on edge).

For stud wall construction, your concrete slab on grade will need to have an appropriately thickened edge in order to support weight of walls, or a continuous footing and foundation will need to be poured.

Ultimately post frame construction, not stick wall construction, is most probably going to be Raymond’s best route to go when considering investment and ease of construction.

Crawlspace Skirting, Adding Spray Foam, and Rafters

Today the Pole barn Guru discusses crawlspace skirting, adding spray foam, and building with rafters instead of trusses.

DEAR POLE BARN GURU: I am planning on building a post frame home with a standard wood framed floor structure. It will have a crawlspace below but will not have concrete stem walls. The building site slopes down, some of the crawlspace may be excavated below grade, some areas will be above grade. Looking for ideas for skirting the crawlspace to provide the most appealing look at exterior side and keep out water and pests. TRENT in WALLA WALLA

DEAR TRENT: In areas where your building’s crawl space would involve excavation below grade, it might behoove you to place a permanent wood foundation between columns (https://www.awc.org/codes-standards/publications/pwf-2015).  In other areas most of our clients have run steel siding down to four inches above grade, just like typical post frame construction.

DEAR POLE BARN GURU: Looking to spray foam the Hansen pole barn we built.

I have some questions.  We ordered the kit with roof insulation and it was installed when built. I’m thinking of leaving the ceiling open so the trusses are exposed. Can the foam be sprayed over the insulation? If the insulation is removed can the foam be sprayed directly to the roof? If so do I just close off the ridge vent? On the side walls do I just close off the top that opens to the eaves? MARK in MT. AIRY

DEAR MARK: Make sure to use only closed cell spray foam. I have heard arguments both for and against using spray foam against either a weather resistant barrier (such as Tyvek) in walls or a reflective radiant barrier. For this one I would defer to an answer from whomever will be doing your foam application, since they will have to warranty their installation. Certainly you can spray foam directly to inside of steel panels – I did this in a recent addition to my own post frame building home. You will need to close off both vented ridge as well as soffit.

DEAR POLE BARN GURU: Is it possible to build a pole building roof structure with rafters rather than trusses? FRED in GREENBANK

DEAR FRED: As long as building can have either interior columns, or single sloped (within reasonable span limits) it can certainly be raftered, rather than trussed. Please see this prior article in regards to pole and raftered buildings: https://www.hansenpolebuildings.com/2012/08/stall-barn/

 

“Rafter”Spacing, Old Posts, and Electrical Wiring Solutions

Today the Pole Barn Guru answers questions about “rafter” spacing, how to best dispose of old posts, and where to run electrical wiring.

DEAR POLE BARN GURU: Can I place rafters 48” apart on 24 x 40 pole barn with steel roof? DAVE in BAY CITY

DEAR DAVE: I will interpret your “rafters” to be Midwestern casual term for roof trusses. If so and properly designed to support required loads, trusses could be placed every four feet. In order to support roof steel, purlins would need to be laid either across top of, or joist hung in between roof truss top chords.

You should consult with an RDP (Registered Design Professional – architect or engineer) who will be providing plans for your building for determination of required loads, purlin spacing and size.

 

Ask The Pole Barn GuruDEAR POLE BARN GURU: I have a telephone post fence that I no longer want. How to I dispose of it? It is big and heavy. MINETTE in LUCAS

DEAR MINETTE: Whether large or small challenges, or a question doesn’t even pertain to post frame buildings, I do my best to answer them all and give best possible advice.

I’d start with trying to give it away using Craigslist and/or Facebook – you just might find a taker!

 

DEAR JUSTINE: (Ha ha! Fooled you as reader JAMES questioned Hansen Pole Buildings’ wizardress of all things materials – Justine, who forwarded it to me):

I have a construction question… I need to run wiring in the walls of the pole barn, and I wanted to be sure that drilling through the poles wouldn’t be a problem. I can either run all the wires up into the ‘attic’, then down where they are needed, which wouldn’t require boring holes through the poles, but would use a lot more wire, or I can run horizontally, and bore holes through the poles.

What is the recommended way? Are there limits to how many/large the holes can be?

Thanks. JAMES in LEBANON

DEAR JAMES: An article has been written specifically to address your question: http://www.hansenpolebuildings.com/2013/08/electrical-holes/

 

 

 

Attaching Horse Stall Posts to Trusses

Attaching Horse Stall Posts to Trusses – Just Say No!

Horse housing can be a significant piece of pie for post frame (pole barn) builders and building kit suppliers when economies are good. From 2007 to 2012, as U.S. economy tanked, horse populations decreased by 10%! Well, economies are cyclical and with a strong recovery a need  for stall barns has increased.

What surprises me – only a very small number of what I would term “best designed” stall barns – designed with sufficient airflow for healthiest horses, are being built. These buildings do not have prefabricated roof trusses, instead they are built using poles (columns) and dimensional lumber rafters. For more reading about pole and raftered stall barns: https://www.hansenpolebuildings.com/2012/08/stall-barn/.

I scratch my head when I see clients investing in clearspan buildings to be used for equine housing. I am most familiar with pole and rafter buildings with poles every twelve feet, to accommodate building horse stalls. Reader SCOTT in DAYTON writes in as one of these who now facing some challenges of trying to correctly construct stalls in his clearspan building. He writes:

“I am installing dividers and horse stalls in a clear span structure. Interior posts need to be added two of which will attach to one of the rafters and serve as supports for the dividers and a stall front. Each post will consist of three 2×6 cribbed boards with treated lumber for the below grade pieces. The tops of the posts will be saddles so that I can through-bolt into the rafter. My question is: how do I set these so that they are neither supporting or hanging from the rafter? Do I dig the holes just shallow enough so that the top of the posts will be snug to the rafter or just hang them and fill the holes with concrete? Thanks!”

Mike the Pole Barn Guru responds:

Even after nearly 20 years as a Midwest import I am still not used to prefabricated wood roof trusses being referred to as “rafters”. Unless you have prior truss manufacturer engineer sealed approval you should not be connecting columns to truss bottom chords. While it may seem added support of a tightly fitting column might be an assist, under a snow load it may actually place loads upon truss in spots not designed for support and can lead to a catastrophic failure.

You may want to consider using either a solid sawn pressure preservative treated column, or a glu-laminated column with bottoms treated for structural in ground use, as opposed to nailing up a three ply 2×6 column where members can separate over time.

I’d be prone to place columns deep into the ground and completely backfill the holes with premix concrete, stopping columns well below trusses.

 

 

A Stone Base Floor? Trusses vs Rafters, and Entry Door Install

DEAR POLE BARN GURU: I have a 40 x 24 pole barn with a 4 inch stone base floor. Can I place 2×4 grid framing 24 in on center with 3/4 inch T&G 4 x 8 sheets for light weight shop usage? No vehicles. JEFF in SYCAMORE

DEAR JEFF: Some ifs – if your site is drained so as to not have excess moisture beneath the building, if the subgrade is thoroughly compacted and if you have a well-sealed vapor barrier underneath, then it might work. Be prepared for the possibility of frost heaving. Both the framing and the sheathing should be pressure preservative treated to a minimum UC-4B level to prevent possible deterioration.

 

craigslist pole barnDEAR POLE BARN GURU: You compare scissor trusses to conventional trusses, but I see nothing about using beams instead. I’m aware of only one post frame supplier that provides beam systems in lieu of trusses. Are there any down sides to using beams and avoiding trusses all together? RACHEL in ST. LOUIS

DEAR RACHEL: My only guess would be you mean rafters, not beams. Or it could be your intent is a ridge beam supporting rafters. In any case, the answer is going to come down to time, money and reliability. If an alternate system to prefabricated wood roof trusses is to be used, it should most certainly be a design which has been thoroughly reviewed and sealed by a Registered Professional Engineer. Obviously prefabricated wood roof trusses are most highly prevalent because they offer the advantages without the expense of time and labor.

DEAR POLE BARN GURU: Can I install a 36″ steel entrance door before the exterior girts are applied? DONAVON in EAGLE GROVE

DEAR DONAVON: In most cases, the columns on one or both sides of the entry door are trimmed off above the door and supported by a wall girt which runs between two roof supporting columns. If your particular application has framing on both sides of the door which is attached to the roof system, then it would probably be possible to install the entry door prior to the wall girts. I am not seeing any apparent advantage to doing so and it would add to the possibility of inadvertent damage to the door.

 

Deep Fascia Overhangs

The definition of Fascia from the sum of all human knowledge (Wikipedia):
“Fascia (/ˈfeɪʃə/) is an architectural term for a vertical frieze or band under a roof edge, or which forms the outer surface of a cornice, visible to an observer.

Typically consisting of a wooden board, uPVC or non-corrosive sheet metal, many of the non-domestic fascias made of stone form an ornately carved or pieced together cornice in which case the term fascia is rarely used.

The word fascia derives from Latin “fascia” meaning “band, bandage, ribbon, swathe”. The term is also used, although less commonly, for other such band-like surfaces like a wide, flat trim strip around a doorway, different and separate from the wall surface.
The horizontal “fascia board” which caps the end of rafters outside a building may be used to hold the rain gutter.”

In layperson’s terms, the fascia is the outside member of an overhang which is extended past the eave side (where the rain water drips or snow slides off) off a building.

For most residential structures, the fascia board is a 2×6 or 2×8, which provides an overall fascia height approximating five to seven inches depending upon slope of roof, etc.

Open OverhangsThere are some cases where it is advantageous to increase the height of the fascia, these would include (but are not limited to):
Aesthetics (aka looks) – some people like the look created by a deep fascia overhang.
Supporting signage – on commercial buildings having a deep fascia on the eave side of the building several feet in height can allow for signs for a business or businesses to be placed.

We recently ran across an instance where a client needed to have a tall door in the endwall of his new post frame (pole) building, however his Planning Department had a strict limitation upon the allowable height of building sidewalls.

Enter the thinking caps.
By the creation of a deep fascia overhang, the eave height (read more on how eave height is measured here: https://www.hansenpolebuildings.com/2012/03/eave_height/) was able to be increased by several feet, without the need for longer siding – meeting the strict requirements of the Planning Department!