Technical
The purpose of this American Institute of Timber Construction (AITC) Manufacturer Product Report is to detail provisions under the International Building Code (IBC) and International Residential Code (IRC) for approval of Unalam structural glued laminated timber (Glulam) for use in buildings and other structures. The IBC and IRC are the model building codes generally adopted nationwide, regionally, and locally, regulating building design and construction. This Report also contains information for architects, engineers, and builders, for the design and specification of Unalam Glulam, as well as installation and construction information.
Product Details
We have created these technical notes specifically for design professionals. Use the menu to get tips for designing straight and curved glulam members as well as general information on species, grades, and finishing options.
STRAIGHT GLUED LAMINATED TIMBER MEMBERS
Our standard glulam beams simply and attractively provide support to roofs and floors. Factory made to give clear span lengths, the dimensions of these members are designed to give maximum economy in size and cost. Finger jointed laminations maintain high strength and eliminate weak defects. A variety of finishes are available, from industrial to architectural to premium grade. Load bearing beams can be pre-cambered to compensate for deflections. These standard beams can be accurately cut to length and arrive on site sealed or stained (if required) and ready for erection. Laminated posts are also available. Manufactured for interior or exterior use, these members provide a stability that is not possible in standard timber.
SIZES
Glulam beams are specified by actual finished dimensions. Any dimensions are possible, but it is most efficient to use the following standard sizes.
All profiles are available with or without camber.
CURVED GLUED LAMINATED MEMBERS
The flexibility of glulam and the expertise of Unalam can turn into reality almost any shape a designer can imagine. The best economics can, of course, be realized by following the minimum radius guidelines listed below.
We recommend using Southern Yellow Pine (SYP) for curved members due to its material properties, particularly radial tension strength.
TYPES
Pitched & Tapered Beams
These glulam beams follow the straight roof pitch on their top edge while the bottom forms a radius curve. Pitched and tapered beams taper from the tangent point to a minimum end depth to provide maximum economy. Optimal roof pitch is 2/12 to 3/12, though other roof pitches are possible. Inside radius of 20′-0″ or more allows use of 2″ nominal laminations. Use “beam” stress combinations, e.g. 24F-V3.
Curved Beams
Glulam beams with constant cross section and radius for barrel or dome roof profiles. Use “beam” stress combinations, e.g. 24F-V3.
Tudor Arches
A traditional 3-hinge arch design commonly used in glulam structures. Outside edge of glulam follows the straight wall (arch leg) up to the eave (arch knee), then follows the straight roof slope (arch arm.) Arch leg and arm taper down to the base and peak depths. The interior side of the arch uses a continuous ply, curved at the knee. Standard inside radius at the knee is typically 7′-0″. Optimal roof pitches are 3/12 or higher. Use “beam” stress combinations, e.g. 24F-V3.
Complex Curves
Reverse curves, combination curves, S-curve arches, spirals – we have done them all, and would love the challenge of something new!
Horizontally Curved Beams
Glulam beams that curve in plan use plies that are oriented vertically, therefore the finished height of the beam is based on standard glulam widths. Larger cross sections can be made via special wood manufacturing processes. We can even fabricate complete circles. Use “other member” stress combinations, e.g. #47/1:8.
Sizes
Specify glulam by true finished dimensions.
Widths:
3″, 5″, 6.5″, 8.5″, 10.5″ standard, 12″, 14″, 16″, 18″, 20″ extra wide
Depth:
Multiples of lam thickness based on:
-Minimum radius 20′-0″ or greater: 1.375″ laminations (standard 2″ plies)
-Minimum radius 7′-0″ or greater: 0.667″ laminations (standard 1″ plies)
GLULAM WOOD SPECIES AND APPEARANCE GRADES
We offer a variety of options that affect the finished appearance, strength, and longevity of our glulam products – from raw materials to coatings. Here is an overview of the variables that should be specified for your next glulam job.
RAW MATERIALS
Wood Species
Southern Yellow Pine (SYP) makes up the majority of our work. It is our material of choice for economy and strength – and is highly recommended for curved members. Douglas Fir, Alaska Yellow Cedar, Red Maple, and other species are also available.
Treated Lumber
For glulam members exposed to weather or harsh outdoor environments, we offer CCA and Penta treated material. Partially exposed members can even be fabricated with treated and non-treated zones.
Forest Stewardship Council™ Certification
We are Forest Stewardship Council™ (FSC®) chain-of-custody certified, making us the right choice for LEED certified projects. FSC® material must be specified.
APPEARANCE GRADES
Appearance grade refers to visible knots and defects on the wood surface. One of the following grades should be specified:
AITC Premium
For jobs where appearance is of critical importance. Allows only very small knots and voids on exposed surfaces. Any other voids and defects are plugged with clear wood inserts, not just wood filler.
AITC Architectural
The most common appearance grade for Unalam jobs. Ideal for exposed projects, where the appearance of natural knots and small voids in the wood is acceptable. Any other voids and defects are plugged with clear wood inserts, not just wood filler.
AITC Industrial
For projects where glulam will be hidden from view or appearance is not critical. Sides of members are planed, but voids or other defects on the edges of laminations are not repaired.
STRENGTH PROPERTIES
Design values are available in ANSI 117-2010, which can be downloaded free here.
Typical SYP Combinations
24F-V3 for simple span beams
24F-V5 for continuous span beams
#47/1:8 or #49/1:10 for columns or other members not loaded primarily in strong axis bending
SURFACE FINISHES
Stains and Sealers
We recommend all glulam members receive a factory coat of penetrating stain or clear sealer. Please ask for samples of our standard stains.
Surface Texture
Typically a smooth, factory-planed finish with eased corners is provided for all members. Other textures are available, which simulate rough sawn lumber, hewn timber, etc.
End Grain Sealer
Penetrating end sealer is factory applied to all cross-grain cuts in the factory.
Flame Retardant Coatings
Coatings which affect flame spread values of glulam are available. However, we recommend they be field applied because surface marring during handling can occur with these coatings.
STEEL CONNECTIONS AND HARDWARE
We design and fabricate custom steel connections and hardware for almost all of our glulam construction projects. Contract documents can show fully detailed connections or specify whether factory designed connections should be fully concealed, partially concealed (bolts visible but plates concealed,) or fully visible.
STEEL FINISH
Our default steel finish is galvanized hardware (bolts, nuts, shear plates, etc.) and gray primer on steel plates and shapes. Other options include: All galvanized, all powder coated, and stainless steel.
STEEL GRADES
Typically steel shapes and plates are A36, and bolts are A307.
Engineering and Design Services
Unalam produces full shop drawings for review and field use on all of our custom projects. In house engineering services are available ( including PE sealed shop drawings and calculations in many states) for the glulam, decking and glulam connections that we supply
