Post Frame Shouse Column Options – Risk vs. Reward
Loyal readers will recall a recent post involving GREG in KENTWOOD (https://www.hansenpolebuildings.com/2020/09/dont-want-pressure-treated-columns-in-the-ground/).
Our discussion continues and I share below:
“Mike,
Thanks for the quick response.
If I was a sane man, not sure I am, if properly pressure treated lumber will last a few generations, why would I not go with that?
- The time to DIY yourself wet set brackets could add a few weeks to the projects. ( I probably have the time.)
- Using a Perms Precast Columns which are $152 each will be costly with probably needing 50 to 60 posts. (Adds about $10k to project)
- I might be able to be talked into using pressure treated poles.
- Does the plastic help or does it add more risk of trapping moisture or other?
- I will cost out each method, on a little “nerd chart” to determine what risk and reward I can accept.
Do you think your source for the pressure treated poles is better and more consistent than say a Menards or other source a non-builder would get supplies?
For a (2) story would you use laminated posts or solid?
Would you use only treated on the first 8’ to prevent shrinkage and warping at a (2) story height?
This will hopefully be all my questions prior to submitting a plan.
Thanks Mike!”
Greg is probably going to be very satisfied with his end result – he is reading, asking questions and learning. Hours spent in preparation can save tens of thousands of dollars later.
I live in a million dollar shouse (shop/house) with roughly 8000 square feet finished. It has glu-laminated columns with pressure treated bases, embedded in the ground. I could easily have chosen any alternative solution, as cost was not a deciding factor.
Wet set brackets are probably only marginally more time consuming, however to minimize concrete needed for piers, you will (or should) be using insulated forms. When all is said and done plan upon roughly $100 per column for budget.
Precast columns have not just column investment, they are also heavy to handle onsite and do require a concrete footing or bottom collar to prevent settling.
Plastic sleeves might be effective, however I felt they were redundant given modern pressure treating technologies.
In most cases, it is impossible to walk into a lumberyard or big box store and get UC-4B treated lumber, it most usually has to be special ordered in. Our providers know, in advance, of this being our expectation (not to mention minimum requirement by Building Codes).
I would go with true glu-laminated columns (I did on my own building). They will be lighter, straighter and stronger than solid sawn columns and not have challenges as do nailed up columns. Lower portions are typically treated so laminations are a minimum of six feet of treatment (usually a 6′, 8′ and 10′ member are bottom treated segments). Pressure treating does not prevent shrinkage or warping – shrinkage is limited due to this lumber being kiln dried after treating in order to get moisture content low enough for proper glue adhesion. Warping is a by-product of laminations being oriented so lumber grain is all one direction and is a rare occurrence with glulams.
Ask as many questions as you need to feel confident in your decisions.
Mike the Pole Barn Guru
Reader STEPHEN contributes a question regarding high density polyurethane foam for column backfill:
Besides not being Code conforming, there is an issue of cost. Your suggested product provided at The Home Depot will provide a volume equal to five 80 pound bags of concrete (or 1/10th of a yard) for $37.63 or $376.30 per yard. With pre-mix concrete prices being roughly $100 a yard, concrete being Code conforming and not contributing to decay any more than would high density foam, it seems to me to be a no brainer.
“Long-term post and lumber durability tests provide insight into the expected durability of wood products that have been treated to AWPA standards and properly handled during construction. This review of the durability data from a test site in southern Mississippi indicates that the expected durability of creosote-treated wood is in excess of 50 years, and that of wood treated with pentachlorophenol, ACZA, or CCA exceeds 60 years. No failures have occurred in lumber specimens treated to intermediate or high retentions of pentachlorophenol, ACZA, or CCA formulations. The expected durability of specimens treated with copper naphthenate was more difficult to interpret because of conflicting results between tests with lumber and post specimens. However, the post specimens indicated durability in excess of 60 years, even at retentions substantially below those currently used commercially. Some caution is needed in extrapolating the durability observed in these test specimens to in-service structures, as the specimens are not subjected to the same mechanical loads or potential damage during construction. Conversely, comparison of the results from this site to reports from other locations suggests that these results might underestimate potential durability in more northern climates.”
This resulted in a plethora of alternative pressure preservative treatment chemicals being introduced which, on the surface, sound like a veritable alphabet soup – ACQ, CA-B, CA-C, MCA, etc.
Over the past few decades, I’ve been involved in several pole building projects on the Hawaiian Islands, and they all had one thing in common – the use of pressure preservative treated lumber throughout, included the prefabricated wood roof trusses. The use of pressure treated wood has been standard building practice in Hawaii and the building codes require all structural wood framing to be constructed with it. In 2003, Hawaii banned use of CCA pressure treated wood, due to it containing arsenic.
Even electroplated galvanized nails, which were the predominant fasteners used with CCA (Chromated Copper Arsenate) pressure treated lumber, are not acceptable for use with ACQ (Alkaline Copper Quaternary) and CBA (Copper Boron Azole) pressure treated lumber. The zinc content in the coating of these nails is insufficient for long-term resistance to the corrosive action by the chemistry of some of the new treatments.
