Tag Archives: structural engineers

Does an IRC Design Work for Most Residences?

In my humble opinion (and in one word) – no.

I have opined in past articles as to what Code is applicable to post frame (pole) building construction: https://www.hansenpolebuildings.com/2018/10/what-building-code-applies-to-post-frame-construction/.

Recently Louisiana engineer Steve M. Sylvest (www.sylvestengineering.com ) sent an email to Structural Building Components Association addressing challenges with non-engineered structures, particularly residences. Again, I stand on my soap box – if an engineer was not responsible for structural design of your building…..who was?

Here is a major excerpt from Mr. Sylvest’s email:

I read your article The Structural Design Process of a Building with interest since it relates to some observations I have made for some time. There is a wide disparity in design and execution of the structural portion of structures, particularly residential, in this region. Some are reasonable, but many are not. Yet they get built and permitted and pass inspection.

In the immediate area, many residential projects largely do not qualify to be designed per the IRC prescriptive standards (are at least some key portions do not since exceeding the limits). Many must be mimicking construction details they have seen and deem to be adequate. Some are obviously far from good mechanics (e.g. hinged tall walls, lack of adequate shear or braced wall lines, connections not consistent with load path, etc.). The permitting and inspection process does not seem to be at a level to distinguish when structural elements are outside of typical IRC provisions.

A majority of the residential projects are designed by Building Designers, though a smaller number by Architects. Few have structural engineers involved. The range of structural information on the design documents (of the ones I have seen) range from zero to more often just a collection of standard details based on IRC conventional framing, with little or no specifics. A small minority actually provided a viable level of specific information to tell the contractor what to do. Most leave it to the framer to do what he deems is reasonable. The inspectors must have a few hot-button feature to look for, but otherwise must not be too aware.

steel pole buildingVery few residential (1 and 2-family) structures in this region use CM components (e.g. roof or floor trusses or wall panels). Many use Engineered Wood Products (EWP). These are typically designed (for gravity loading) and supplied through a distributor. The process is similar to a performance specification leading to deferred submittal, but most often without any design engineer input at the design stage nor any review of the submittals. For gravity loading, this process usually works well. A couple of things are usually missing. One is any consideration to lateral loading paths in the building and the other is a design professional in responsible charge to confirm the members, load paths, and connections all are consistent with the rest of the structure. So, the final result is a structure with a few well-engineered EWP products (for gravity loading), and some portions of the structure (almost) in line with IRC, but the remaining is just whatever the particular framer deemed adequate (similar to what he is used to seeing).

Several things work against making meaningful changes. Most builders, even high-end ones and builders desiring quality results, do not realize there is a gap (or wide range of results getting delivered). Likewise, the buyer is unaware. Permitting and inspection is not attuned enough to discriminate. Nobody is interested in adding more cost. The already –completed projects are still standing (and working for the most part, as far as they know).”

Mike the Pole Barn Guru adds:

If you are considering investing in a new building, especially for use as a home, barndominium or shouse(shop + house) – insist upon a Registered Professional Engineer having sealed plans and calculations specific to your building project on your site. This is not an expense, it is an investment!

The Cheaper Roof Style, Plan Sales, and Engineering!

DEAR POLE BARN GURU: For a span of 84 feet, which is cheaper, a single slope roof or a gabled roof? ANTHONY in NEW ORLEANS

DEAR ANTHONY: At almost any span a gabled roof is going to be less expensive. At an 84 foot span, without question it will be significantly so.

DEAR POLE BARN GURU: I am curious if you sell custom plans without the kit. I am interested in a plan for a 26 x 26 pole garage with a room above and dormer on each side. I would like to use local supplies.

Thanks for the info. AIMEE in KALISPELL

Engineer sealed pole barnDEAR AIMEE: Thank you very much for your interest. Hansen Pole Buildings is unique in that we have formed relationships with suppliers all over the United States – including local to you! These relationships allow for the bulk of your materials to be delivered to your site, from suppliers who are generally within just a few miles of you. Due to our tremendous buying power, we are able to negotiate prices on materials far below what either the general public, or even builders would be able to get. We get you the benefits of both worlds – close to home and at a great price.

Many companies, such as ours, do not sell “just pole barn plans”.

Why? Many reasons.

1. We have streamlined our process for efficiency. This means by the time you get your plans, we are far into a ton of series of steps happening concurrently – and have done much of the “work”….which has a cost. People are willing to pay an architect several thousand dollars for house plans, but they are unwilling to pay an appropriate amount for the work involved to produce truly custom pole building plans.

2. You get the plans from us, but decide to purchase your materials “elsewhere” and then are disappointed because you paid a lot more than you thought it was going to cost.

3. Worst of all, you purchase materials that don’t match the pole barn plans from someone else and your building contractor does not build to our plans and blame us when the Building Department won’t sign off on your building.

DEAR POLE BARN GURU: I am building a home on a steep slope, what size foundations should I use for a 8 inch x 8 inch steel column embedded in the foundations, how square and how deep should each column foundation be? Regards ALAN in SAN RAMON COSTA RICA

DEAR ALAN: My step-sister and her husband lived in Playa Potrero for many years, so I have an affinity for Costa Rica.

There are so many variables which would go into the calculation for an adequate footing for your columns. The best solution is to get in contact with the structural engineer in Costa Rica who designed your home. He or she might need to have some soils tests done by a geotechnical engineer to determine the allowable bearing pressure of the soils at your site (I know I would certainly want to have this information). Your engineer will be able to calculate the live and dead loads which will be applied to the column (and hence the footing) to be able to provide you with the information on your foundation which will keep your home standing for generations to come.

 

Building Engineer: One Who Should Know Better

Over the years we have provided, to clients, several post frame buildings in a county in California which will remain unnamed in this blog.

This particular county has an actual registered building engineer who does the structural plan reviews.  Sometimes this can be a good thing, sometimes a challenge.

One of our clients recently submitted a plan (produced by one of our engineers and including all of the calculations) for a new barn. This particular building had a wood floor, supported by floor joists. The floor joists were attached to gambrel (old barn profile) roof trusses at each end, by joist hangers. The sidewall columns (and trusses) were spaced at 12 foot on center. The greatest distance spanned by the 2×10 #2 floor joists is 11’8”.

The building engineer who did the review came up with:

“Please take another look at the 2×10 floor joists. Using a live load of 40 psf, which may not be

applicable if the area is used for storage, #2 DF fail in bending. #2 Hem-fir is even worse.”

Now the lovely thing about the International Building Codes is the span tables listed in Chapter 23 for things like – floor joists!

It really does not take rocket science for the average lay person to look at Table 2308.8(2), “Floor joist spans for common lumber species”. The table lists Douglas Fir-Larch, Hem-Fir, Southern Pine and Spruce-Pine-Fir. Going down the 2×10 column, to the 24 inch joist spacing area, lets the reader know the least span for any of these species, in #2 grade, is 12-5.

NDS BookIn the event the building engineer did not choose to open the code book, there are free online resources which can be accessed. The American Wood Council has a very handy one at www.awc.org, which I use frequently.

My real peeve here – this plan check has now created unnecessary work for our engineer, and creates skepticism in the client’s mind.

Oh, by the way, our engineer had provided the calculations which prove the floor joists specified do work, the reviewing engineer neglected to look through them!