Engineered Lumber in a BC Custom Home: I-Joists, LVL, Glulam and Trusses

Walk onto one of our framing sites in Buckingham Heights or Government Road once the second floor is on and count the sawn lumber in the floor. There is not much. The joists are I-joists. The beam carrying the great room ceiling is laminated veneer lumber or glulam. The roof is a stack of trusses that arrived on a truck with drawings. The studs, plates and blocking are still plain 2x6, and that split is the right one.

Owners ask about this a lot, usually after seeing an I-joist for the first time and wondering whether that thin web can carry a floor. It can. Here is what each product does, why the structural engineer calls for it, and how we handle it through a Burnaby winter.

What "engineered" means, piece by piece

I-joists. A floor or roof joist shaped like a capital I. The web is oriented strand board, the flanges top and bottom are laminated veneer or sawn lumber. The shape puts the material where the stress is, so the joist is deep, light and straight. It has no crown, so the floor above it is flat, and it does not dry into a twist the way a green 2x10 can.

LVL and PSL. Both are structural composite lumber. Laminated veneer lumber is thin veneers glued with the grain running one direction. Parallel strand lumber is long strands pressed together, denser and used where the loads are heavier or the member is a post. These are the beams, headers and rim boards on most of our jobs.

Glulam. Layers of sawn lumber glued face to face into one deep member. Glulam is the beam you leave exposed, because it is real boards you can see. The BC Building Code requires glued-laminated members to be fabricated in plants qualified under CSA O177, which is why a glulam arrives with a stamp and a certificate rather than just a grade mark.

Roof trusses. Sawn lumber chords and webs joined with pressed metal plates, engineered by the truss plant for the exact roof shape. A truss roof clears a wide span with no interior bearing and goes on in a day.

Why the engineer specifies them

Part 9 of the BC Building Code, the part that governs houses, is written around lumber frames of small repetitive structural members, or engineered components, with a cap of 12.20 metres on the span of any single member. The same section gives span tables for sawn joists and rafters, and separate tables for built-up and glulam floor beams. Stay inside those tables and a house can be framed without an engineer designing each member.

Nobody building a custom home in Burnaby stays inside those tables. The moment the plan asks for a great room with no post in the middle, a kitchen island with a floor above it and no wall below, or a second floor that cantilevers past the main floor wall, the sawn tables run out. The engineer then designs the member under Part 4 of the code, which sends wood structural members to CSA O86, Engineering Design in Wood. That is where the I-joist span charts and the LVL load tables come from.

(We link the readable 2018 code text on the province's free portal because it is the edition posted in full; the engineer stamps against the current 2024 edition, which came into effect March 8, 2024.)

Three things the engineer is buying with engineered wood:

• Span. A deep I-joist crosses a room a sawn joist cannot. An LVL or PSL beam carries a floor over an opening a built-up 2x12 beam cannot.
• Flatness. Engineered members arrive straight and stay straight. Large-format tile, wide-plank hardwood and level kitchen islands all depend on a floor with no hump at mid-span.
• Predictability. A stamped product has a published strength. Sawn lumber varies board to board, and the tables account for that with margin.

The design conversation about ceiling height and volume usually comes back to this. A double-height space with a bridge across it, or a vaulted ceiling with no collar ties, is a beam problem before it is an aesthetic one, and engineered wood is what solves it without steel.

Where sawn lumber still wins

Walls. A 2x6 stud at 400 millimetres on centre, with plates and blocking cut from the same pile, is the right material for nearly every wall in the house. Short floor spans in a bathroom wing or a mudroom can stay sawn. Anything treated for ground contact or exterior exposure, like deck framing, is sawn lumber. Sawn is also easier to modify on site, which matters when a plumber needs a notch the engineer has already allowed for.

We put engineered wood in the floor and the long beams, because that is where the difference shows up in the finished house.

Rain, and why the wet season changes the handling

The BC Building Code requires that lumber be at or below 19 percent moisture content at the time of installation. That is the rule for all framing. Engineered wood adds one complication: it takes on water differently from sawn lumber and it is less forgiving about it.

An I-joist web is oriented strand board. Leave a cut end in a puddle for a week and it swells. LVL soaks in from the edges of the veneers. Glulam is sealed at the plant and holds up better, but a wrapped bundle that gets opened in October and left in the rain until December is still a problem.

So on a Burnaby build that frames through the wet months, the rules on site are simple. Bundles stay wrapped until the day they are used, stacked on dunnage off the mud and sloped so water runs off. Cut ends get sealed. The roof goes on as early as the sequence allows, because the fastest way to dry a floor is to stop raining on it. Before insulation, the framing gets a moisture meter, and anything reading high waits. The same logic drives how we plan the whole shell, which we cover in building through BC's wet season.

One more code detail that matters at the foundation: framing that is not pressure treated and sits on concrete in contact with the ground has to be separated from that concrete by polyethylene film or roll roofing. That includes the sill plate under a wall full of engineered posts.

Holes, notches and fire blocks

The code's drilling and notching rules in Part 9 are written for sawn members: holes not larger than one quarter of the member's depth and at least 50 millimetres from the edges, and notches only on the top near the bearing and no deeper than one third of the depth. Those rules do not transfer to engineered products.

An I-joist is drilled through the web only, at the sizes and locations on the manufacturer's hole chart, with no-cut zones near the supports. Cut a flange and the joist has to be replaced. An LVL or PSL beam gets no holes at all unless the engineer has approved that exact hole on the drawings. Glulam is the same. On our jobs the plumber and the HVAC trade get the hole chart before rough-in, and the framer marks the no-drill zones on the joists with a lumber crayon so nobody has to guess.

A deep I-joist floor is a gift to the mechanical trades until somebody cuts a flange. Then it is a replacement joist and a week.

Icon Projects Team

The other rule that lives in the same floor is fire blocking. The BC Building Code requires fire blocks to separate concealed spaces in walls, floors and ceilings from one another, at each floor level in a wall, and wherever a pipe or duct passes through, the block has to be made good around it. The acceptable materials are listed in the same subsection and include gypsum board, plywood or OSB, and 38 millimetre lumber. A deep floor with open webs and a soffit dropped below it is exactly the kind of concealed space that section is written for. The engineer's drawings show the structure; the fire blocking plan is the framer's, and we walk it before drywall.

Trusses, seismic and the frame inspection

Roof trusses are engineered by the truss plant, and the code sets a floor under them: trusses not designed under Part 4 have to carry a stated ceiling load and stay within the deflection limits in the truss table. In practice every truss package we receive is engineered, and the City of Burnaby wants to see that. Its inspection brochure lists, for the frame inspection, a truss layout reviewed by the structural engineer of record, signed and sealed truss drawings, and a field review memo from the structural engineer. We keep that package in the permit bag on site before we book the inspection.

The seismic side uses the same members. Shear walls, hold-downs and the load path from roof to foundation run through the rim boards, the beams and the posts the engineer sized, and a point load from an LVL beam has to land on a post, then on squash blocks through the floor, then on a footing. We walk through that chain in seismic design in a Burnaby custom home.

What we check before insulation

Before the walls close, the framing gets a walk with the drawings open. Every beam sits where the drawing says, with the bearing length the engineer called for. Every hanger has every nail hole filled, with the hanger nails the manufacturer specifies rather than whatever was in the pouch. Squash blocks sit under every point load. I-joist webs have holes only where the chart allows. Blocking and fire blocks are in. The engineer's field review is done and the memo is in hand.

That walk is the last time anyone sees the floor system in a house that will stand on it for a century. It is worth an hour.

Frequently asked questions

What is an I-joist and why do Burnaby builders use them instead of 2x10 joists?

An I-joist is a floor joist shaped like the letter I: a thin web of oriented strand board with a flange top and bottom made of laminated veneer or sawn lumber. It spans further than a sawn joist of similar depth, it arrives straight with no crown, and it does not shrink or twist as it dries. At Icon Projects we use them on most Burnaby floors because the open plans owners want need spans that a sawn 2x10 cannot make without a beam or post.

What is the difference between LVL, PSL and glulam beams?

LVL (laminated veneer lumber) is thin wood veneers glued with the grain running one way, which makes a strong, straight beam or header. PSL (parallel strand lumber) is long strands of wood pressed together, used where loads are heavier or spans longer, and often for posts. Glulam is layers of sawn lumber glued into one member, and it is the one most often left exposed as a finished ceiling beam. The engineer picks between them based on the load, the span and whether the beam will be seen.

Can engineered lumber get wet during a Vancouver winter build?

It can get rained on for a short time, but it cannot stay wet. The BC Building Code requires lumber to be at or below a set moisture content at the time it is installed, and an I-joist web or a cut LVL end takes on water faster than sawn lumber does. At Icon Projects we keep bundles wrapped and off the ground, seal cut ends, close in the roof as early as the schedule allows, and meter the framing before insulation goes in.

Can I drill holes through an I-joist for plumbing or ducts?

Only through the web, only at the sizes and locations on the manufacturer's hole chart, and never through a flange. The general notching and drilling rules in Part 9 of the BC Building Code are written for sawn lumber; an I-joist follows its own published chart and the engineer's drawings instead. At Icon Projects the plumber and the HVAC trade get that chart before rough-in starts, and the framer marks the no-cut zones near supports.

Why does a Burnaby framing inspection need sealed truss drawings?

The City of Burnaby's inspection brochure for new single and two family dwellings lists, for the frame inspection, a truss layout reviewed by the structural engineer of record along with signed and sealed truss drawings, plus a field review memo from the engineer. The trusses are engineered by the truss plant, and the City wants proof that the house engineer has checked that layout against the rest of the structure. We have that package on site before we book the inspection.

Does an open-plan custom home in Coquitlam need engineered beams?

Almost always, yes. Part 9 of the BC Building Code provides span tables for sawn joists and for built-up and glulam beams, but a wide great room or a floor with no interior bearing wall usually needs a beam beyond what those tables offer. That beam is then designed by the structural engineer, and it is nearly always LVL, PSL, glulam or steel. The same logic applies in Coquitlam, Burnaby or Abbotsford; the code is provincial.

Can a glulam beam be left exposed in a custom home?

Yes. Glulam is the engineered beam most often specified where the owner wants to see the wood, because it is made from visible laminations of sawn lumber and comes in appearance grades. The engineer sizes it for the load and the architect chooses the finish. LVL and PSL can be exposed too, but their surfaces are usually wrapped or painted rather than shown.

Do engineered wood floors feel bouncy?

A properly designed one does not. The BC Building Code's Part 9 span provisions require floor joists that are not taken from the sawn-lumber span tables to meet both the loading and the vibration criteria, and I-joist span tables are published with that in mind. Bounce usually comes from a joist pushed to the far end of its table, a missing row of blocking, or subfloor that was nailed instead of glued and screwed. At Icon Projects we keep spans inside the comfortable range and glue every sheet of subfloor.