 the boards of NLT, but friction-fit together with hardwood dowels instead of nails. The dowels hold each board side-by-side, forming a stiffer and stronger connection than the nails in NLT. Each board lamination in a DLT panel is finger-jointed, creating a stiffer and stronger panel than NLT as it eliminates the board splices and butt-joints which are characteristic of NLT.
DLT panels may be processed using CNC machinery, unlike NLT panels (due to the nails). This creates a high tolerance panel which can also contain pre-integrated electrical conduit and other service runs.
Panelized Building Elements
DLT panels are prefabricated in sizes of up to 12 feet wide and 60 feet long. Each panel is put through a panel planer to ensure a dimensionally accurate and planed surface. Prefabricated panels can be factory finished with sealers or stains.
Finish and Geometric Possibilities
DLT is a versatile product, and naturally lends itself to creating unique aesthetics on the exposed face of the panel. Each of the laminations are run through a profile molder, meaning many different profiles are achievable, from notches and reveals to flowing curves.
Curved DLT panels can be created by milling custom profiles into each lamination, creating a flexible panel which, like an accordion, can accommodate curves perpendicular to the span direction of the panel. The radius for these curves is limited only by the bending stiffness of the dowels, which are located centrally in the panel. These panels are created initially flat and then curved into shape on site.
Fluted panels (e.g. 2×4-2×6-2×4) can create a unique soffit aesthetic if exposed, and allow the running of electrical conduits or sprinklers in the gaps.
Unique to DLT as a mass timber product, acoustic profiles can be integrated directly into the bottom surface of a panel. This can help a designer achieve acoustic objectives while keeping the wood exposed and allowing for a wide variety of surface finishes.
Any wood species incorporated in the International Building Code (IBC) and referenced National Design Specification (NDS) for Wood Construction can be used in DLT, as only specified strength and stiffness for each lamination is required. Full-scale panel testing is not required to determine structural performance – a significant advantage to DLT as a product.
As a floor or roof deck, DLT is a highly efficient structural panel. Similar to NLT or GLT (glulam on flat), all of the wood fiber runs in the direction of the span. This provides the most efficient use of material for floor and roof systems which are typically one-way spanning between beams or walls.
From a structural perspective, each individual lamination spans between supports, meaning calculation of the panel stiffness and capacity is simple. The structural design of each lamination in a panel is covered by CSA O86 and the NDS and applicable grading rules. Structurally finger-jointed lumber is used for spans longer than 20 feet, meaning no reduction in strength or stiffness is required for longer panels. This is a big advantage over traditional NLT where butt joints in laminations require a 20 to 30 per cent reduction in panel strength and stiffness (refer to Nail Laminated Timber Design Guide, Table 4.1 and IBC 2015 2306.1.4).
The Uniform Building Code (predecessor to the IBC) has recognized laminated decking since 1927, and the NBC since its first publication in 1941. The requirement for minimum fastening of the boards together ensures that the panel acts as an element and not individual boards. The 3/4″ diameter hardwood dowels in DLT can create the same interlayer shear capacity between boards as the original 20 penny nail requirement specified in the IBC.
Machine stress rated lumber can be used to increase strength and stiffness of the panel.
Diaphragms and Shear Walls
Plywood or OSB sheathing atop the panel gives shear capacity to DLT panels for use as structural diaphragms in floors and walls. The sheathing also allows for simple nailed connections between panels with strips of plywood. The shear capacity of the sh