Tag Archives: building use category

Top Chord Repair, Little Voices, and Building Use

Today the Pole Barn Guru tackles questions about repairing a rotted top chord of an existing truss, a little voice in a contractor’s head, and the use of an existing building on newly purchased parcel.

DEAR POLE BARN GURU: When we bought our property the pole barn on it already had a rotting roof with a hole in it. We are ready to re-roof it, are putting steel roof on it, and two of the truss’s top chords have rot we think they need to be replaced, is there a easy way to get the truss apart to fix this? We are fairly handy people but new to dealing with truss repair. Would appreciate any input. JILL in SOUTH LYON

DEAR JILL: You are good to address this issue now. There is no way to easily take apart a prefabricated wood roof truss when it is in place. Your best bet would be to contract with a Registered Professional Engineer in your area who can do a physical examination and provide an engineered repair.  This is just prudent as if there was to be a future building failure at a non-engineered fix, your insurance company could deny your claim.

If your building has purlins over top of trusses, it may be something as simple as adding another top chord to one or both sides of damaged trusses and bolting through.


DEAR POLE BARN GURU: My client has some old metal trusses. 1 1/4 angle iron top and bottom threads with 1” solid rod cross members 1” high and 28” long.

They are not plated and angled on one end to accommodate mating in the center for a 2/12 pitch roof. They appear maybe to be old single slope trusses or maybe floor trusses. Try angle out the last 4’ on both ends with the top chord and the bottom chord stops.

Anyway he wants to cut and weld clips in the middle to accommodate 2/12 pitch mating surface and on the wall end weld on clips to catch the post.

I’m okay up until he says he only has enough for 7 of these trusses to be made (14 total pieces). He is demanding we put these small trusses on 16’ centers. Use fresh cut true 2×6 milled lumber (ungraded).

No overlaps at the trusses just flush up the ends at each post. No end walls only sidewalks, 18’ high and no plans for lateral supports inside the Trusses running length of the building.

I haven’t built but a few barns all engineered so haven’t had any problems but worried about this red neck engineering. Also no center post clear span 40ft with 4’ overhang past the post. 7 post each side 16’ o/c truss span.


DEAR LEE: Obviously a little voice inside of your head is telling you to run, do not walk, away from this as quickly as possible. I agree with your little voice. There are plenty of clients out there who want to do things correctly, if you do take this mess on and it fails – you are going to be hung out for it.


DEAR POLE BARN GURU: I have recently purchased a five acre parcel with a 40×40 post frame building on it the guy that we bought the property from had this building put up with the idea of making it his home. The trusses are built to have living areas upstairs, it is raw, posts, roof trusses, and metal siding but no plywood under the metal and the posts are back filled construction. I want to do a wood floor just not span forty feet instead do floor joists of twenty feet so my question is can I build from the raw state that it’s in like you would for a normal stick built home or would I need to pour a regular foundation first?. Thank you. JOEL in POCATELLO

stick frame building collapseDEAR JOEL: Hopefully your ‘guy’ bought a fully engineered building, designed for R-3 Occupancy Classification and Use, Risk Category II with deflection limits of L/240 or greater for walls and truss supported drywalled ceilings. All of these will be specified on this building’s engineered plans. If you do not have a set of them, your Building Department may have them on file.

If you are unable to ascertain these conditions, you should retain a Registered Professional Engineer to do an analysis of your building for structural adequacy for your intended use. He or she can also make a determination as to if column footings are adequate to be able to support weight of your raised wood floor. You should not have to go to an extreme, such as pouring a regular foundation.

You may want to reconsider your floor joist span as 20′ will take 2×12 #2 at 12 inches on center and will have an allowable deflection at center of 2/3 of an inch. By having interior supports closer together you can greatly reduce joist dimensions and deflection, increase joist spacing and have a much less costly floor.




Use Categories, Water Leaks, and Matching a House

Today’s Pole Barn Guru answers questions regarding Use Categories, water leaks, and matching a house due to HOA rules.

DEAR POLE BARN GURU: Hi! I am trying to turn my existing barn into a wedding venue. Why am I being classified as A-2 instead of A-3? Our special use permit says we cannot exceed 300 guests and we have less than 12,000 sq. ft. Additionally, we are not serving food or alcohol- the guests must provide their own- ergo we should not be considered a “banquet hall” under A-2… Correct? ALYSSA in ARLINGTON

DEAR ALYSSA: In an ideal world you would have just asked your Planning Department why. In researching your question, I believe your Planning Department is correct – even though YOU are not serving food or alcohol, guests may bring their own. This makes it an “eating establishment”.
A-3 is a group for worship, recreation and amusement uses. It is also a catch-all for other uses not specifically called out. These uses include galleries, religious worship spaces, courtrooms, sports spaces without seating, lecture halls, libraries, museums, pool halls, bowling alleys, transportation waiting areas and funeral parlors.

DEAR POLE BARN GURU: After years our barn is leaking at the bottom during very heavy rains. We have gutters on the sides but it appears to be coming in thru the wood at the bottom below the metal siding. Maybe from hydrostatic pressure any suggestions? CAROL in CLARKSVILLE

DEAR CAROL: Get rid of the water.

pole barn classroomsI realize this sounds simplistic, but it is what needs to be done. Building Codes require sites to slope away from buildings by at least 5%. This would be six inches of drop in 10 feet. If you do not have this type of slope away from pressure preservative treated splash plank at building base, you need to start digging.

Gutter downspouts should not just put water out on top of your ground. This water should be directed into downspout drain lines – moving away from your barn.

Once you have done both of these steps, your “leaking” issues should go away.


DEAR POLE BARN GURU: I live in a neighborhood with an HOA. I can build any kind of building I want, but it must match my house, i.e. Brick or Vinyl Siding (house has both) and a shingled roof. Can a pole building be built with these features instead of metal and will it be just as good? DAVID in GREENSBORO

DEAR DAVID: A beauty of post-frame (pole) building design and construction is you can side and roof them with any materials you can imagine! Not only will it be every bit as good, it will also be more affordable.

You can read about a HOA horror story here: https://www.hansenpolebuildings.com/2016/05/not-mess-hoas/



Use and Occupancy Group Classification Part II

As I said yesterday, in life, most everything is given some type classification whether it’s objective, such as motor vehicle operators’ licenses (automobile, commercial, motorcycle, etc.), or subjective, such as social status (wealthy, middle class, poor). Then there are those who are in “a class all by themselves.” My wife seems to think I fit in this category, which I take as a compliment! Buildings, like much of everything else, are classified, as well.  If you didn’t read yesterday’s blog – or if you did, review it quickly to get your head around the rest of the occupancy group discussion.

Yesterday I discussed “mixed group” classifications of buildings, such as fire stations and office buildings.

To continue, another occupancy group which relies on objective criteria is the High-Hazard Group H. Group H occupancies are assigned based on maximum quantities of materials which pose a physical or health hazard.

These materials may be used for manufacturing or processing, stored in the building, or generated as a product or byproduct through a process. Upon first glance, determining which H occupancy group is appropriate may seem to require a chemical engineering degree. However, material safety data sheets (MSDS) and the quantities involved allow for a practical guide. Discussing the project with a fire plans examiner at the building department can prove helpful as well.

Institutional (Group I) occupancies include buildings with occupants who are under supervised care, living in a controlled environment where they’re limited physically by either age or health, or they have personal liberties restricted by detention for penal or correctional purposes. Group I-3, which includes prisons, jails and correctional facilities, is further subdivided into “conditions.” However, unlike the occupancy subgroups, the five conditions are numbered with increasing risk to the higher numbers.

Residential (Group R) occupancies apply to buildings which are used for sleeping purposes, among the many other uses associated with residential uses. R-1 and R-2 groups apply to buildings which house occupants in large numbers. R-1 includes transient type housing consisting of hotels and motels, while R-2 housing is more of a permanent nature, such as apartments and dormitories. Groups R-3 and R-4 are required to comply with the requirements of the International Residential Code (IRC). R-3 occupancies include single detached houses and duplexes, and R-4 occupancies include assisted living and residential care facilities that have more than five, but less than 16, occupants, including staff.

Returning to mixed occupancies, designers of buildings involving multiple occupancies within the same structure have the option of selecting one of two types of mixed occupancies: Separated or non-separated uses. Mixed occupancies can be considered as “separated” because fire barriers of varying fire-resistance ratings are required between certain occupancies, or mixed occupancies can be non-separated, without any fire barriers.

There is a catch however, as the height and area requirements for each occupancy group used are to be applied to the entire building, and the most restrictive construction type will be applied to the entire building.

Allowable areas and building heights may be increased through consideration of automatic fire sprinkler protection and wide yards around the building.

Additionally, construction types are also of significant importance in properly applying the building code since they establish minimums based on building materials. The establishment of occupancy types is based on years of research and experience, and it is one of the essential building blocks in developing an effective building code.

And I can’t say this enough times…when in doubt take a trip to your friendly building department to discuss your building.  Take along a concise but complete list of all of the “uses” your new building will involve.  It will make your whole project slide along much smoother. These people want to see you build.  Their job is to ensure the health and safety of those using your new building.

Use and Occupancy Group Classification Part I

In life, most everything is given some type classification whether it’s objective, such as motor vehicle operators’ licenses (automobile, commercial, motorcycle, etc.), or subjective, such as social status (wealthy, middle class, poor). Then there are those who are in “a class all by themselves.” Buildings, like much of everything else, are classified, as well.

There are two elements of classification in the building code: occupancy and construction type. This blog is about the essential elements of determining a building’s classification based on its occupancy.

The International Building Code (IBC) establishes the requirements for classifying buildings based on occupancy. Essentially, an occupancy establishes how the building will be used, whether for business, residential, or one of the many other types.

The IBC states, all “…structures shall be classified with respect to occupancy…”. There’s no assignment of responsibility included. Therefore, the Registered Design Professional (RDP – either an engineer or architect) can “legally” determine a building’s occupancy; and the building official, will either concur or not concur with the RDP’s decision during plan review as a part of enforcing the provisions of the code.

As a potential owner of a new building, early discussions with the Building Department can avoid confusion as to which occupancy group will be accepted for the intended use.

The IBC has established 10 occupancy groups, with some having multiple subgroups. These subgroups are numbered with a purpose. The lower the number, the greater the perceived risk is for the occupants. For example, A-1 has large occupant loads in fixed seating. Whereas A-5 is includes seating of large numbers of people for viewing outdoor activities. Assuming the occupancies had equal occupant loads, the A-1 is indoors with fixed seats that reduce egress speed. The A-5 occupancy, although having fixed seats, is outdoors reducing the risk of smoke and heat buildup within the seating area.

The 10 occupancy groups are Assembly (A), Business (B), Educational (E), Factory and Industrial (F), High Hazard (H), Institutional (I), Mercantile (M), Residential (R), Storage (S) and Utility and Miscellaneous (U).

Most of the occupancies are assigned strictly on the building’s intended use, or uses, as most buildings have many spaces which can be classified under more than one occupancy group.

For example, a fire station may have sleeping quarters for the firemen (Residential), office areas (Business), vehicle and other miscellaneous storage areas for the fire equipment (Storage), and a training area (Assembly).

Buildings which can be classified with multiple uses are considered “mixed occupancies.” However, before calling a building a mixed occupancy, it needs to be determined if the additional occupancies can be considered “incidental use areas.” These are spaces which provide minor support to the building’s main occupancy. The IBC provides the criteria for incidental use areas, which typically include storage, mechanical, and other specialty spaces. If a space qualifies as an incidental use area, it will be classified as a part of the main occupancy it’s incidental to.

For example, if an office building (Group B) has a 200 square foot storage area (Group S) within the office area, then it could be considered Group B if it is separated from the office area by 1-hour fire barrier, or is provided an automatic fire-extinguishing system for the storage space only.

Most spaces can be classified solely on their intended use; however, some occupancy assignments are more objective. For example, a room may be used for assembly purposes, but if the space is equal to or less than 750 square feet, then its classification is considered a part of the main occupancy. Using the fire station example above, if the training area is 750 square feet in area, then it will be considered a part of the Business Group. If it’s any larger, then it would have an Assembly Group classification.

Why the 750 square foot limitation? It goes back to the basic definition of “Assembly” occupancy. If the occupant load is 50 or greater, and is used for the gathering of people for various purposes (such as civic, social, or religious), then it’s considered an Assembly occupancy. Taking 750 square feet and dividing by 50 occupants, gives 15 square feet per occupant, which equals the most liberal occupant load factor for an assembly use.

Your head hurt yet?  Don’t worry; your local building department will help you with the use classification of your building.  It will do you no good to “guess”.  My suggestion is to clearly list each “room” and describe what it will be used for, by how many people at any given time.  Then take your list to the building department for a “use category” assignment.  Come back tomorrow. There is more on this topic for discussion.