By Mike Momb – I’ve now surprisingly (especially to me) spent my entire adult life in the post-frame building industry. I’ve been blessed to be a manufacturer (prefabricated light gauge steel plated wood trusses), a supplier of post frame building kit packages as well as a post-frame building contractor.
The general assumption in our industry has always been—‘built on your clear, level site’ (or for those of us who provide kit packages ‘on your clear, level site’). And of course, every job site is clear and most importantly level! What happens when those job sites are not only out of grade, but way, way out of grade?
I happen to own a couple of examples of those ‘way out of grade sites’.
Back in 1937 my great-grandparents bought a lake cabin northeast of Spokane, Washington. The lot the cabin is on is 225 feet deep, measured horizontally. However, with the slope, the lot probably covers well over 300 feet.
My great grandfather actually built a pole building garage, back in the 1930’s! The two-car garage (two Model A’s) was 16 feet wide and 20 feet deep –sounds like a modern tract home garage. With a dozen feet of grade change in the 20 foot depth, Great-Gramps poured a concrete retaining wall to keep the parking lot in place, then set eight cedar logs on top of concrete piers to support the floor…and the cars!
When I inherited the place from my grandparents in 1990, it was time to replace the garage. The cedar posts were showing signs of decay, and there was no way I would ever be able to get two cars in the now-tiny space. The old garage was torn down to the floor to provide a safe deck to work from. The new 22 by 24 post-frame garage was built around the outside of the old one. The remains of the old one was dropped out of the middle, then the floor was framed utilizing 2×14 joists with 2×6 commercial decking over the top to support a nominal four inch thick concrete floor.
Below the car parking area had been nothing but dead air space. A nifty 16×22 studio apartment fit nicely below and afforded practical space for friends and family to visit. By using bonus room attic trusses, the area above the garage became a sweet little office!
Once we moved in, we did get some surprises along the way. Our property happens to be on a point which juts out into the lake. In the early 1950’s the opposite side of the point was re-platted. It turns out the surveyor swung an arc wrong and by the time it got to our lot, it created a 50 foot overlap!!
Long story short, a protracted court case with my neighbor ended up with us winning. Having spent a small fortune in the battle, I just had to utilize the formerly overlapped area to the best possible advantage—not to mention I felt compelled to irritate my neighbor by constructing the largest building I possibly could!
I found that if I followed the property lines, with the obligatory five-foot setbacks, I could construct a 40 foot by 36 foot post-frame building which was only 14 degrees out of square in the formerly disputed area (my lot is a parallelogram).
Just one little challenge…no, not just having to be 14 degrees out of square. It was the once-again 12 feet of grade change. By excavating over 500 cubic yards of rock and soil, I was able to create a clear, level site. Now, how to solve the challenge of the cut out of the hillside?
To begin with, never turn a post-frame builder (as I was at the time) loose with more money than brains. Seriously though, the design challenge was actually a lot of fun.
I decided to handle the high side of the cut as well as steeping down with the grade on the ends, by the use of 8-inch Insulated Concrete Blocks (ICFs). Into the top of the wall were poured steel brackets which allowed for columns to be anchored to the top of the walls. The total structure ended up being three stories high, with the peak of the roof over 40 feet above the ground. The ICFs worked perfectly and afforded a design solution which made the entire project quit doable.
The low sidewall and most of the front endwall ended up with columns being able to be embedded in the ground, with the reduced foundation costs of the embedded columns helping to offset the added expense of the ICFs. Basically I had created a daylight basement.
About 10 years ago, we (Hansen Pole Buildings) provided the new nature center for the Cheyenne Mountain Zoo in Colorado Springs, Colorado. This was also a site with some grade change – 10 feet! By excavating into the hillside, a three-sided concrete basement was poured. A full floor with kitchen and serving areas was constructed above the basement, with the open side of the basement entering onto a single sloping area which could be divided up into three classrooms separated by moveable partitions suspended from the roof trusses.
When it comes to post-frame buildings on top of foundations, the only real limitations become imagination, budget and available space!
In my mind, the creation of a full or partial concrete foundation negates some of the cost savings of post-frame construction, but this is certainly not a reason to walk away from it.
Poured-in-place brackets, such as Perma-Column’s wet-set Sturdi-Wall brackets allow for columns to be mounted to the tops of full or partial concrete foundation walls with relative ease.
We’ve seen a huge upswing in not only the use, but the design from the beginning, in post-frame construction used for residential homes. The great majority of clients are not interested in living upon a concrete slab on grade floor, which leads to a fair amount of crawl spaces. While the least expensive design solution is to utilize an elevated wood floor attached to timber or glu-laminated post-frame building columns, there are those who prefer to have a perimeter concrete, block or ICF foundations.
Whether a crawl space, or a full or partial basement, floor systems are easily incorporated using the same post-frame techniques utilized for second floors and lofts. Systems involving beams and floor joists, I joists, floor trusses, or a combination of some or all become practical design solutions.
Some neat things can be done with the floors too. My post-frame building, towering over my neighbors’, is entirely clear span on the inside. The second floor happens to have a four foot step-down, providing a 10 by 36 foot exercise area with a panoramic view of the lake to help take away the pains of overworked muscles and treadmill boredom.
As a post-frame building contractor or building kit supplier, if you are unfamiliar with combining your building system with foundation walls or multiple raised wood stories, now is a good time to have a sit-down discussion with your RDP (Registered Design Professional—engineer or architect). In combination with them, do some serious brainstorming as to what options can be offered to best meet the dreams and aspirations of your clients.
And never again fear digging a big hole! RB
The above article was written by Mike Momb for Rural Builder magazine for the column, “Behind the Hammer”. Momb is technical director for Hansen Pole Buildings, LLC of Browns Valley, Minn. His daily post-frame blog, as well as his weekly “Ask the Pole Barn Guru” column can be followed at www.hansenpolebuildings.com/blog/.