Tag Archives: posts rotting

BIB’s Insulation, In-Ground Posts, and Rodents

BIB’s Insulation, In-Ground Posts, and Rodents

DEAR POLE BARN GURU: I’m still in processing with the county to get permits for our new Hansen home building but in the meantime I’m trying to figure out insulation for our raised floor. County requirements (I’m assuming IBC code) requires R30 floor insulation. The building floor design wound up using 2×6 floor joists so I’m trying to figure out how to get R30 worth of insulation in a 2×6 joist cavity? I’m planning on either BIBS or blown/dense pack cellulose for the walls and ceiling and there’s no problem there, but the floor is an issue. I’d rather continue cellulose or BIBS in the floor but I’m not seeing a clear solution( I can do spray foam if absolutely necessary but I’d really rather not). Do you have any suggestions? LONNIE in COLORADO SPRINGS

DEAR LONNIE: I know you have read my blogs, so you know I am a huge fan of BIBs, having used the system in two of my own buildings. I previously have had some qualms about the use of closed cell spray foam insulation, however my physics teacher son had good results with it in the remodel addition to his home, so we used it when we added the elevator shaft to the rear of our own home and I am now a convert. You can get R-30 with as little as four or so inches of closed cell spray foam and it absolutely seals up everything.



DEAR POLE BARN GURU: I will be building a post and beam barn (40×48 or thereabout) on my property and would like a central loft that I can finish for additional living space. I have been advised that posts concreted into the ground are unlikely to last but I’m a bit concerned about a two story structure with posts bolted to concrete piers… What would you normally recommend? MIKE in LEXINGTON

DEAR MIKE: Whoever is giving you the information about the lifespan of properly (key word being properly) treated pressure preservative treated columns not lasting, knows not what they are talking about.

I personally own three multistory post frame buildings, including our home which has 8000 finished square feet and a roof peak 44 feet above the ground. Every one of them has treated columns in the ground.

While columns bolted to piers will work in most situations, why go to the expense and extra efforts?


DEAR POLE BARN GURU: I was wondering if you had any ingenious ideas about how to keep mice coming in from sliding barn doors? We have stuffed steel wool and sprayed foam into the corrugated hollow sections of the walls but they’re still able to come in through the gaping hole under the sliding door.  Any ideas how to resolve that? MELANIE
carport barnDEAR MELANIE: I always warn people who are planning on using sliding doors – as long as you do not mind your neighbor’s cat getting into your building, they are great. No matter what you do with a sliding door, short of affixing it so it will not open, the mice are going to get in. An adult mouse only needs a hole the size of a dime in order to enter your building. By its nature, the sliding door needs to do one thing to function – slide, and in order to slide it has to have space to be able to clear the members which are under it. If your building does not have a concrete slab on grade floor, you could pour a concrete curb across the door opening, however the bottom of the door will still need to be adjusted up high enough to clear the concrete given the fluctuations in expansion and contraction of both the door and the building due to seasonal changes in temperature and humidity.

If you truly want to eliminate the problem, replace the sliding door with an overhead door. In the meantime, it might behoove you to invest in a good barn cat or two.


Pressure Treated Posts: When Future Building Owners Think They are Engineers

When I was just a little tyke, my Mother used to watch Art Linkletter’s “House Party”. A highlight of his show was the segment, “Kids Say the Darndest Things”.

I have my own version, “Potential Building Owners Say the Darndest Things”.

Our Building Designer Lauri seems to be a magnet for these lately. Here she shares another one….

“Speaking of the poles. I don’t want to sound like a picky little prig or an officious jerk but I do have a requirement about the bottoms of the poles. I don’t know what your standards are for the poles, but I do not want the bottom of the poles sitting in a concrete cup.

When the holes are dug for the poles I would like them to be dug about a foot deeper than needed. Then the bottom of the hole can be filled with at least 6 inches of cracked limestone or 2B river wash stone.

The poles are then set on the stone and an additional 3 or 4 inches of stone are added to the holes. Then set your cardboard casing and fill it with concrete. This method allows for moisture to drain out of the bottom of the pole thus reducing wood rot. If the poles are set deep enough I think you can get away with out using concrete, that is your call, but if you do use concrete the bottoms of the poles have to be able to drain. That is carved in stone.”

Ah, where to even begin?

Let’s talk about pressure treated posts. Rotting fungi need water to work. Other conditions necessary for wood rot to develop include a supply of oxygen and temperatures between 32 and 90 degrees Fahrenheit. (Decay stops below 35 degrees and above 100 degrees.) Wood becomes susceptible to rot if its moisture content exceeds 25 to 30 percent. Keep wood dry, it will literally last for centuries. On the other extreme, if the wood is 100 percent saturated with water, the decay fungi won’t get the oxygen they need. Decay won’t occur, and the wood can last for centuries.

Nowadays building columns are pressure preservative treated for structural in ground use. They are designed to last lifetimes, under the most adverse conditions. If the soil at the site drains well, there is no reason to place rock or gravel beneath or under a column to “drain water away”. If the soil at the site does retain water, any gravel in or around the base actually becomes a collection basin for water, rather than allowing water to drain “off”.  In a quick summary, this customer came up with a poor investment in rock and the labor to dig deeper holes. Plus, this person added chance of the building settling due to inadequate compaction of the stone.

Other previous blogs have covered topics such as the lifespan of pressure treated posts, the need for concrete column backfill to resist settlement, uplift and over turning, as well as why not to use “cardboard casing” (better known as sonotubes).

While I appreciate customers who are concerned about the longevity of their buildings, it is best to leave the structural design of buildings to the experts – registered design professionals (RDP’s).  A RDP (or P.E., i.e. Professional Engineer) has not only the complete educational preparation, but also the decades of experience needed to combine proper structural design and efficiency of materials.

Pressure Treating Glulam Columns

We recently had one of our engineers specify the use of glulam pressure treated columns to support one of our custom designed pole buildings. The client was concerned about pressure treated glulams in the ground, so it was time for some heavy duty research.

According to the American Institute of Timber Construction (AITC), structural glued laminated timbers (glulams) can be treated with waterborne preservatives after laminating.

While in general, the laminated timber industry recommends against using waterborne preservative chemicals to pressure treat structural glued laminated timbers after bonding, this recommendation is only intended to prevent appearance problems caused by treatment and subsequent re-drying. Pressure treatment with waterborne chemicals after bonding does not generally make the laminated timber structurally unfit. Treating structural glued laminated timbers (glulams) with waterborne chemicals after bonding may be a viable option for applications where appearance is less critical, like for pole buildings.

Adhesives used in modern glulams are extremely durable and are considered waterproof. Glulam timbers treated after bonding will accept treatment and resist decay similar to treated sawn timbers of the same species and will perform similarly in service. If the appearance of this product is acceptable to the consumer, it can be used successfully in applications where treated wood is required. Provided the structural requirements of the application are met (meaning – was the right size and grade of pole selected for factors such as wind speed, snow load, etc.), treated glulam timbers can be used in place of treated sawn timbers.

Pressure-treatment is a process of applying preservative chemicals to wood to increase resistance to decay. Pressure-treated wood is used in applications where wood will be wet and subject to decay.

Pressure treatment of properly manufactured structural glued laminated timber members will not cause delamination. Delamination refers to adhesive failure leading to separation of bond lines. Adhesives used in modern glulam products must meet stringent standards for moisture resistance and durability. Additionally, adhesive bonds in glulams must also pass rigorous daily testing for strength and durability. Consequently, delamination is very rare in structural glued laminated timber whether it is pressure-treated after bonding or not. Checks can occur along bond lines due to stress concentrations between laminations and are often mistaken for delamination. The presence of wood fiber separations or torn wood fibers at the bond line is the key distinguishing characteristic of checks .

If glued laminated timbers are treated after bonding, dimensional changes caused by saturation of the wood with the water-borne preservatives and their carrier followed by subsequent re-drying may result in raised grain and warping, checking, or splitting.

Some species do not accept treatment well and require incising while others can be treated successfully without incising. Southern Pine is generally not incised, while Douglas fir typically requires incising for adequate penetration of the preservative.

Bottom line is, can you use glu-lams in the ground for pole buildings if they are pressure treated for in-ground use?  Absolutely!  The treatment process to get them to the PT level may cause them to look not quite as pretty as the varnished beams in your cathedral ceiling, but they will be every bit as strong. And rest assured…they will not rot. If you don’t believe me – maybe you will believe the American Institute of Timber Construction.