Frequently Asked Questions

What is “whole house design”?
Although they’re separate design elements, roof trusses and floor components act as an integrated system in your house. Each element depends fully or partially on the components of the other element. In whole house design, the roof and floor components are designed to act together as one system.

When designed separately, a truss designer may not be made aware of critical information about the floor design – and vice versa. When you deal with the KOTT design team, you get the benefit of whole house design – trusses and floors are designed to work together optimally, versus simply to co-exist.

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How should I brace the web in my trusses?
Bracing reinforces the web in your truss to prevent it from buckling, and ultimately ensures that your roof truss will perform as intended. There are two ways to brace your web – continuous lateral bracing and T-bracing. Use continuous lateral bracing when there are 3 or more trusses of identical configuration being erected next to each other. Use T-bracing when there are less than 3 trusses, or when there are trusses of different configuration being erected next to each other. To learn more about bracing, ask for our Guide to Web Buckling Prevention.

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Why should I choose an engineered wood floor over a dimensional lumber floor?
By design, engineered wood products are more stable and consistent than conventional lumber. I-joists are manufactured to precise tolerances and will not shrink, warp or twist, eliminating the performance-related problems – including squeaks – that are associated with conventional lumber joists.

I-joists are also engineered to weigh less and span further than solid sawn lumber joists, enabling you to reduce or eliminate bulkheads and design longer spans. I-joists remove many of the limitations of traditional floor designs, giving you the freedom to design the large rooms and open concepts popular in today’s architecture.

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How are Nascor I-joists different from other I-joists on the market?
The Nascor product family includes the cost-effective Easy-I® NJ Series I-joist. The Easy-I features a unique 2x3 vertical nailing surface, enabling it to be handled and installed like conventional lumber with traditional framing techniques. This means the product can be used not only as joist, but be nailed together and used as rim board or beam in place of costlier alternatives. Alone or in combination with Nascor’s deeper, stronger NJH and NJU joists, the Easy-I can be designed as an entire floor system, to create a cost-effective floor that goes beyond the limitations of 2x10.

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How do I make sure that I do not exceed the allowable I-joist spans in my floor design?
Nascor has published a series of detailed floor span tables that take into account joist type, on centre spacing, glue vs. no glue and other factors. Download the Nascor Specifier Guide, where you will find the span tables on page 3.

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I got three quotes on my engineered floor system. Why are they all so different?
There can be a great deal of variance in the design of a floor system, based on the overall quality desired. Factors such as joist depth, thickness of sheathing, and the use of glue, bridging or blocking can impact the stiffness, and therefore the performance, of the floor. Before comparing the bottom line on your floor quotes, make sure you are comparing apples to apples. What is the on centre spacing of the joists? Is the floor glued as well as nailed? Are the hangers included? If you’re not sure how your floor has been designed, ask the supplier for the specifications used to make sure your quotes are truly comparable.

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Do I need my truss or floor drawings stamped by an Engineer?
Most straightforward designs can be submitted for permit or finalized for manufacture without the review of a Professional Engineer. Designs that include components outside the guidelines of the Building Code, or designs that include engineered wood products that have not been evaluated by CCMC (Canadian Construction Materials Centre) require the drawings to bear the seal and signature of a Professional Engineer.

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What is backing?
Backing is the material required for final framing prior to drywall, such as lumber installed between the wall studs to give additional support for drywall, handrail brackets, cabinets, or towel bars. Backing enables items to be screwed and mounted into solid wood rather than weak drywall. A simple rule of thumb is that backing can be budgeted at 25% extra to the lumber already in the house.

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What is LVL?
LVL, or laminated veneer lumber, is a layered composite of wood veneers and adhesive. LVL is a solid, highly predictable, uniform lumber product because natural defects such as knots, slope of grain and splits have been dispersed throughout the material or have been removed altogether. In residential construction LVL is often used for structural framing and is a good alternative where open web steel joists or light steel beams might be considered.

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How is lumber graded?
Most lumber is visually graded by qualified lumber graders. They inspect each piece and apply visual rules to establish its grade, which determines its structural design value. While visual grading works well, increased demand for high performance lumber for highly engineered truss systems has led to demand for more automated techniques. See What is MSR lumber, below.

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What is MSR lumber?
MSR, or machine stress-rated, lumber is manufactured to conform to the National Lumber Grades Authority’s product standard and is graded mechanically. Lumber is fed into mechanical evaluating equipment, which measures and records stiffness, assesses strength and applies an MSR grade mark on the lumber. MSR lumber is also visually checked for properties other than stiffness which might affect the suitability of a given piece.

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What is finger-joined lumber?
Finger-joined products are made by taking shorter pieces of lumber, machining a “finger” profile in each end of the short pieces, adding an adhesive and squeezing the short pieces together to make a longer piece of lumber. Like other engineered wood products, finger-joined lumber is becoming popular as a result of its dimensional stability, as well as the straightness that results from stable short lengths being combined during manufacturing. Finger-joined products are subject to structural tests to ensure they meet the requirements set out by the North American lumber grading system.

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