Tag Archives: soil bearing capacity

Building Department Checklist 2019 Part II


Yesterday I covered seven of what I feel are 14 most important questions to ask your local building department.  This not only will smooth your way through permitting processes, but also  ensures a solid and safe building structure.

Let’s talk about these last seven….

#8 What is accepted Allowable Soil Bearing Capacity?

This will be a value in psf (pounds per square foot). If in doubt, err to side of caution. As a rough rule – easier soil to dig, weaker it will be in supporting a building. A new post frame building will only be as solid as it’s foundation, and it’s foundation will be only as strong as soil it rests upon.

Some jurisdictions (most noticeably in California and Colorado) will require a soils (geotechnical) engineer to provide an engineered soil report, spelling out actual tested soil strength.  Other states may have requirements as well, so be sure to ask ahead of time.

#9  Is an engineered soils test required?

If so, get it done ahead of time.  Don’t wait. It’s easy to do and there are plenty of soil (geotechnical) engineers for hire.

#10 What is your Seismic Category (such as A, B, C, D-1, D-2)?

While rarely do potential seismic forces dictate design of a post frame building, there are instances where they can.  A high seismic potential, with high flat roof snow load and low wind load will be one case. Other case will be when you are considering a multiple story structure.

#11 Are wet-stamped engineer signed and sealed structural plans required to acquire a permit?

Some Building Department Officials will say no to this, yet during plans review process they request structural engineering calculations to prove design, or (worse yet) they make wholesale changes to plans, based upon how they think a post frame should be constructed.

Engineer sealed pole barnMy recommendation – invest in engineered plans. It becomes an assurance a registered design professional has verified your building will meet Code mandated loading requirements. In some cases, insurance companies offer discounts for buildings designed by an engineer. It’s certainly worth asking your agent for one!

In some cases, Building Permits will be granted with only requiring engineer sealed truss drawings. We do not condone this practice, as it creates a false sense of security.

Are exterior finished (showing roofing and siding) elevations required with building plans? Will more than two sets of drawings be needed for permit submittal?

#12 Verify Building Risk Category.

Most buildings not frequently occupied by public (not a home, business or municipal building) represent a low hazard to human life in event of a failure and are ASCE (American Society of Civil Engineers) Category I. This information can be found by Building Officials in IBC Table 1604.5 (not to be confused with Use and Occupancy classifications from IBC Chapter 3).

#13 In areas with cold winters, is frost depth greater than 40”?

All building columns or foundations must extend below frost line to prevent heave. We don’t design for any depth less than 40”, and have designed for up to seven feet deep in some areas!

#14 Does the Building Department have any unusual Building Code interpretations, amendments or prescriptive requirements for non-engineered buildings which could affect this building?

If so, get a copy from your building department for us, or anyone else whom might be considered to be a provider for your building project.

Even though “the Code is The Code”, there are a plethora of local folks who think they have better ways or better ideas than world’s smartest structural minds, who have actually written the Code. And once again, I can’t stress enough: build only from plans sealed by a Registered Design Professional (architect or engineer). It will make life easier all around when it comes to getting your permit, even if you have been told seals are “not required”.

No one inside or outside of a permit office wants a construction process to be any more difficult or challenging than necessary.  Being armed with correct information (after doing homework of course) will be a solid step in the right direction.


How Should I Backfill My Pole Barn Holes?

How Should I Backfill My Pole Building Holes

This is a subject which is repeatedly brought up. Usually it is ones who are constructing a post frame building which was not designed by a registered design professional (RDP – architect or engineer). The wrong answer could easily lead to a catastrophic failure of the building!

Reader JOE in ROCHESTER writes:

“I am in the process of building a relatively small pole building. 16x24x8. I’m having trouble finding the right answer to the back filling the pole question. The local Inspector will be coming to measure the depth of the holes (42” to the top of the footer) but other than that they didn’t give me any spec on back filling or diameter and thickness of the concrete footer. My question is what do you recommend for footer size and how should i back fill the holes around the poles? 42” of concrete around the poles seems like excessive to me and just back filling with earth doesn’t seem right either. Any advice would be much appreciated. Thanks.”

Mike the Pole Barn Guru advises:
My educated guess is the local building authorities issued you a permit to construct without requiring you to submit engineer sealed plans. All this ends up doing is leaving things to chance – which you are quickly finding out. Column embedment (depth and diameter of the holes), thickness of concrete footing, concrete collars, etc., are a function of many different variables.

Among these variables include – the soil bearing capacity of the earth at your site, weight of building with a code minimum snow load, design wind speed and exposure, building eave height and roof slope, is it fully enclosed, roof only or some or all of a wall open? Any one of these could affect the outcome.

Ultimately you should have a registered professional engineer or architect design the column embedment for you. From judicious experience, assuming a fully enclosed building with wind rated doors and properly tied into a four inch nominal concrete slab on grade, your engineer would probably require these as minimum: eight inch thick 18 inch diameter concrete footings. Two sticks of 1/2″ diameter rebar driven through the lower portion of the column, one each direction and sticking past the column four to six inches each side. A Concrete bottom collar probably 10 inches tall and the same 18 inch diameter, with the balance of the hole backfilled with compactable materials well compacted.