Rosboro Treated Glulam

Wet-Use vs. Dry-Use

Wet-use and dry-use are terms that are associated with in-service conditions. Usually a glulam member is exposed to water on an intermittent basis only. Any wetting is typically followed by a drying cycle, and the product never reaches a consistent wet-use condition. This situation is classified as dry-use.

The technical measure of wet-use is accepted as consistent moisture content within the beam of 16% or greater. A wet-use condition is rarely reached unless the beam is submerged in water or subjected to an artificially humid moisture condition. For example, using the chart below, a beam in an environment having a constant relative humidity of 80% and a temperature above 70° F will not reach a consistent moisture content of 16% or greater. Since a combination of high relative humidity and temperature outside of this range is seldom reached in the U.S., ambient air conditions rarely result in a wet-use classification. If there is any question regarding use condition, a licensed design professional should be retained to determine if wet-use design adjustments apply.

Wet-Use Graph

Rosboro Treated Glulam technical information.

Rosboro Treated Glulam

All-Season Beam & Columns

Rosboro Treated GlulamHere's the glulam that can brave the elements. Rosboro Treated Glulam beams and columns are made from southern pine and then treated to resist rot, decay, and insect attack, making this product the ideal choice for above-ground and severe-weather applications. Excellent for decks, porches, and balconies, Rosboro Treated Glulam offers ease of use in the forms of straight beams and columns that match standard framing widths and depths.

Treated Glulam Beams

Our 24F 1.8E Treated Glulam Beams, featuring a balanced layup, are pressure treated with Permapost Hi-Clear II, a clear industrial wood preservative that guards against mold, bacteria, and insects, including the Formosan termite. Hi-Clear II, a clean, non-swelling, non-leaching treatment, that is intended for above-ground exterior applications. For more information on Hi-Clear II, please visit our technical reference page.

Rosboro Treated GlulamBeams Are Available in Common Sizes:

  • Widths: 3-1/2" and 5-7/16"
  • Depths: 9-1/2", 11-7/8", 14", 16" and 18"

Columns Approved for Ground Contact

Rosboro Treated Glulam Columns are pressure treated with a mineral-spirit borne copper naphthenate preservative that provides an ideal fungicide and insecticide for the long term preservation of glulam columns in both ground contact and above-ground uses. This treatment is effective against the dampwood termite, drywood termite and subterranean termites including the Formosan termite. Rosboro recommends that columns be placed on a pier block, but if the column is used in a direct ground contact application, then it should sit in a gravel bed that allows proper drainage. This treatment is intended for exterior applications only and has a color range between chocolate brown and dark green. Click here for more information and design values.

Rosboro Treated GlulamColumns Are Available in Common Sizes:


  • 3-3/8"
  • 5-1/4"
  • 7"


  • 3-1/2"
  • 5-1/2" 
  • 7"

Restricted Uses and Precautions

Rosboro Treated Glulam Beams and Columns should not be used in marine applications such as docks, marinas, and standing-water conditions. Gloves should be worn when handling treated products, and dust masks and eye protection should be worn when cutting treated beams and columns. Always follow site, handling, and disposal instructions provided by Materials Safety Data Sheets (MSDS) available on our technical reference page.

Recommended Hardware, Resealing, and Finishing

Moisture and decay-resistant Rosboro Treated Glulam helps protect the areas around hardware connections; however, field fabrication, trimming, hole drilling, and minor surface damage should be sealed with copper naphthenate (available at local home centers). Though Rosboro uses treatments that are non-corrosive to metal, we recommend using hangers and fasteners specified for treated wood products such as hot-dip galvanized or stainless steel.

Rosboro Treated Glulam

Code Recognized

Rosboro glulam is manufactured in accordance with ANSI Standard A190.1-02, which is a code-recognized national consensus standard for glulam, using wet-use adhesives complying with ASTM Standard D2559. The lay-up combinations EWS 24F-V5M1/SP and Combination Number 50 are recognized under ICC-ES Report ESR-1940. Rosboro's glulam production is inspected and certified by APA-EWS.