Tag Archives: glu-laminated columns; glu-laminated posts; glu-lam strength

Friends Don’t let Friends Stick Frame

Oh the misconceptions arm chair engineers have when it comes to what can be done with post frame construction. For the most part – if you can imagine it, we can design it! Here is a case in point shared by our friend Neil:

DEAR POLE BARN GURU: I have limited floor plan on my lot, looking at a 24w x 64L size post frame building, 14 or 16 foot open height workshop area for lift and heavy truck work and a full second floor for an office, light storage, etc, (40psf live load). This would put the sidewalls between 20 and 22 feet. I believe I can clear span the 24 feet with modern engineered joists, but at this point does it still make sense to use post frame construction? Friends of mine have concerns about column loads, footing capacity, and suggested to just pour a full foundation, stick frame with it to 16′ and build a second floor and go up from there and put trusses on. NEIL in CLEVELAND

DEAR NEIL: Not only is post frame construction going to be the most practical solution, it will also be the most economical. Having to pour a continuous foundation is painfully expensive (read more here: https://www.hansenpolebuildings.com/2011/10/buildings-why-not-stick-frame-construction/). Another issue with trying to stick frame a 16 foot high wall – the Building Codes will not allow it unless you have an engineer sealed design, further adding to the expense.

While “I” joists might be able to span the 24 feet successfully, it will probably be much more practical to do with prefabricated wood floor trusses (https://www.hansenpolebuildings.com/2014/09/floor-trusses/), as they can be designed to limit deflection (read about deflection here: https://www.hansenpolebuildings.com/2015/12/wood-floors-deflection-and-vibration/)  and afford the ability to run duct work and plumbing through the webbing. In order to get everything you want to fit in your new building, you are probably looking at an eave height of around 27 feet. You will want to be talking with your Planning Department to see if there will be height restrictions.

Post frame building columns are very strong in the compression (weight bearing) direction and getting columns 32 feet long is not a problem, as glue-laminated columns are easily available in this length. Footings can be easily designed to support all of the live and dead loads which will be imposed upon them by your new post frame building.

On your second floor, if you intend to go with a 40 psf (pounds per square foot) live load, you will be restricted to residential use. Office space requires 50 psf and light storage is 125 psf. Design the floor for what you will actually be using the space for and have no regrets later!

Glulam Column Sizes

Glu-laminated columns are a laminated composite product manufactured from high-strength lumber. By using multiple plies of materials, natural defects are randomized creating greater column strength and a higher degree of reliability.

glulam columnsHansen Pole Buildings provides glulam columns manufactured by several different companies, so there are some slight variations. This article will speak more to the commonalities between manufacturers and give a broad overview.

A fairly climate controlled environment is required for glulam fabrication, as the phenol resorcinol glues being used to join the end finger joints and individual plies together require a fairly stable temperature for proper curing.

Most post frame building glulam columns are manufactured from a #1 grade Southern Yellow Pine (SYP) lower portion, which is pressure preservative treated to UC-4B (structural in ground use) specifications and then kiln dried after treatment (KDAT) to moisture content of 15% or less.

The upper portions are most typically either #1 SYP or 1650 msr (machine stress rated) SPF (Spruce-Pine-Fir), either of which is kiln dried. Having the proper moisture content is critical to good adhesive bonding in the glue line.

Individual lower and upper members are finger jointed and the joint is glued together. Good finger joints are actually the most challenging part of the entire manufacturing process. Finger jointing allows for columns to be fabricated up to (depending upon the manufacturer) 64 feet in length, with no butt (square-end to square-end) joints.

Once the joints have cured, each member must be planed. This opens up the wood cells to accept the phenol resorcinol glue uniformly. Each member is then run through a planer which reduces the thickness of the board to from 1-1/2 inches as it was originally milled, to 1-3/8 inches.

The plies are then face glued and secured into presses where they are squeezed under pressure. Once the glue has cured, the columns are removed from the presses and planed to remove excess glue and any abnormalities.

After this final planing, a glulam made from three 2x members will typical measure about 4-1/8 inches in width. For a 2×6 the final depth will be 5-3/8 inches.  A 2×8 will be 7-1/8 inches in depth. Four plies will be about 5-1/2 inches in width. While custom dimensions can be created by planing down larger members, the utilization of these dimensions creates the least possible waste and allows for the most value for the investment.

What I like about glulams is they have a high strength to weight ratio (comparing lumber grade to same lumber grade).  I can move a good sized glulam beam by myself, or with a buddy, without having to get out the heavy equipment.