LVL, Glulam and Beams You Never Drill Without Approval
Why this matters
A beam is the one member in a house where a single hole can matter more than a run of them in joists. A joist carries its own strip of floor. A beam or header collects the load of every joist, wall and post that lands on it and delivers it to two or three points, and engineered beams are usually sized close to what that load needs, because that is what makes them economical. A 2 in hole that would be harmless in a joist can land in exactly the place a beam has no capacity to give up.
This card covers laminated veneer lumber (LVL), glued-laminated timber (glulam), parallel strand lumber (PSL) and the solid sawn or built-up headers over openings: why any hole, notch or cut in one needs approval, how to tell what you are looking at, and what to do when a duct, drain or cable run is blocked by one. For joists and studs, see related: Notching and Boring Limits in Wood Framing.
The rule and where it comes from
For engineered beams, the code gives you no field allowance at all. The IRC (R502.8.2 in the 2021 edition, as adopted by your jurisdiction) prohibits cuts, notches and holes in engineered wood products except where the manufacturer's recommendations permit them or a registered design professional designs them. LVL, glulam and PSL are engineered wood products. So a hole is legal only if the manufacturer's literature for that specific product and application allows that hole in that location, or an engineer says so in writing.
Some manufacturers publish small-hole allowances, many do not, and none of them is general. Where an LVL or PSL manufacturer does allow holes, it is typically a narrow allowance: small round holes, in a zone near the middle of the depth, away from the ends and away from bearing points and concentrated loads, and often for some applications (a joist, a rim) and not others (a beam or header). The allowance belongs to that product line. If you cannot name the product from its stamp and find the published allowance, there is no allowance.
Sawn lumber beams and headers are not exempt either. A built-up header of 2x12s over a window follows the sawn-lumber notch and hole rules as a starting point, but a header carries concentrated loads from the jack studs and whatever sits above, so the prescriptive joist rules do not describe its stresses well. Treat any header as a beam: no holes without someone who can answer for it.
Why a beam is different
Three properties of a beam make the cut-anywhere-small instinct wrong.
It carries concentrated load. Every joist hanging from a flush beam, every post or bearing wall above, and every jack stud under a header puts load into the member at one place. The stresses near those points are higher than an even-load calculation suggests, and a hole near one is a hole in the most stressed wood in the member.
Its tension edge is designed, not incidental. In a glulam, the laminations are graded and placed: the highest-grade laminations go at the bottom, the tension face, because that is where a simple-span beam fails. A notch or hole in the bottom laminations cuts through the strongest wood in the beam, which the beam was sized around. Glulam beams are often stamped with a top marking for this reason, and a beam installed upside down has its weakest laminations on the tension face.
It may be cambered. Many glulam beams are built with a slight upward curve so they settle flat under load. A beam that has a camber is under a design condition you cannot see from the floor, and a cut changes how it deflects.
How to tell what you are looking at
| Member | Field cue |
|---|---|
| LVL | Thin veneer layers visible on the edge, running the length; often two or three plies nailed or bolted together; a stamp with manufacturer, grade and size |
| Glulam | Stacked laminations about 1-1/2 in thick visible on the side; a stamp often showing grade, layup and sometimes a top marking |
| PSL | Long strands of veneer pressed together, a dense streaky look on the face; a stamp |
| Built-up sawn header | Two or three pieces of dimension lumber, often with plywood or a spacer between, over an opening, sitting on jack studs |
If a beam is boxed in drywall, the cues are its location (over a wide opening, under a bearing wall, running across the middle of a basement on posts) and its depth (a member deeper than the joists, or flush with them and carrying them in hangers). If a member carries other members, treat it as a beam until you know otherwise.
When a run is blocked by a beam
Work the options in this order, because each one is cheaper and faster than the one after it.
- Go around it in the same plane. A different joist bay, a different register location, a different stack position. Most blocked runs are blocked because the route was picked before anyone looked at the framing.
- Go under it. Drop the run below the beam inside a soffit. In a basement this is usually the fastest answer. The IRC (R305.1 in the 2021 edition, as adopted) allows beams, girders, ducts, pipes and other obstructions in a basement to project to within 6 ft 4 in of the floor, so a soffit in a basement has a knowable floor to stay above. Check your jurisdiction's adopted edition for local changes.
- Go over it. Rarely possible in a finished house, but in an attic or an open floor above, the run can sometimes rise over the beam.
- Ask for an approved hole. Only when the first three have genuinely failed. This takes days to weeks and may come back as no.
What to walk in with when you ask. The manufacturer's technical support or an engineer can only answer a complete question. Send: the stamp information or a clear photo of it; the beam's size and number of plies; its span and where each bearing point is; everything that lands on it, including joists, posts, bearing walls and any point load above; the hole size and its exact location, measured from the nearest bearing and from the top and bottom edges; and photos showing the beam in context. A request that says "can I put a 6 in hole in my LVL" will get either no answer or no.
A worked example: a return trunk against a flush LVL
A tech is adding a central return to a finished basement family room. The plan routes a 14 by 8 in rectangular return trunk across the basement ceiling from the furnace to a return grille in the family room. The floor joists are 2x10s (9-1/4 in deep) at 16 in on center, hung on both sides of a flush beam: two plies of 1-3/4 by 11-7/8 in LVL, spanning 14 ft between a steel column and the foundation wall. The beam's top is flush with the joist tops, so its bottom sits 11-7/8 minus 9-1/4, or 2-5/8 in, below the joists, already boxed in a small bulkhead. The finished ceiling is drywall on the bottom of the joists at 7 ft 6 in above the basement floor.
The joists run perpendicular to the beam, so the trunk can run inside one joist bay, parallel to the joists, from the furnace to the beam, and inside the matching bay on the far side from the beam to the grille. The bay is 14-1/2 in wide and 9-1/4 in deep, which takes the 14 by 8 in trunk. The only problem is the 3-1/2 in wide beam in between.
What the tech does not do. Passing the trunk through the beam would mean a 14 by 8 in opening in a member 11-7/8 in deep, two-thirds of its depth, in a beam carrying the joists of half the floor above. There is no manufacturer allowance anywhere near that size, and no question worth asking.
Option 1: around it. The grille's location was chosen for the room's layout, not for the framing. Moving it to the furnace side of the beam removes the crossing entirely. The owner says no; the grille stays on the far wall.
Option 2: under it. The trunk drops out of the bay before the beam, passes under it inside a short soffit, and rises into the matching bay on the far side. The soffit has to clear the beam's 2-5/8 in projection plus the 8 in trunk, plus about 1 in for framing and drywall, so it drops 2-5/8 plus 8 plus 1, or 11-5/8 in, below the ceiling. The ceiling is at 7 ft 6 in, which is 90 in. 90 minus 11-5/8 leaves 78-3/8 in, or 6 ft 6-3/8 in, under the soffit. That is above the 6 ft 4 in the code allows obstructions to project to, with 2-3/8 in to spare. The soffit runs about 3 ft along the bay, centered on the beam. No joist and no beam is cut.
The record. The tech photographs the beam stamp, the hangers and the soffit framing, and notes on the job that the beam was not drilled, that the soffit clearance was measured at 6 ft 6-3/8 in against the 6 ft 4 in minimum, and that the route was the owner's choice of grille location.
What would have changed the answer. If the ceiling had been at 7 ft 0 in, 84 in, the same 11-5/8 in soffit would leave 72-3/8 in, or 6 ft 0-3/8 in, which is under 6 ft 4 in. Then option 2 fails and the choices become a shallower trunk (a duct-design question: a 14 by 6 in trunk carries less air at the same friction), the moved grille, or option 4. Option 4 for an opening that size in a two-ply LVL carrying hangers is almost certain to come back no.
The failures that come from beams
A hole that was small enough. The most common beam damage is not a huge cut. It is a 1 in cable hole or a 2 in drain hole drilled through a header or LVL because it was smaller than holes the same trade puts through joists every day. Size is not the test for a beam. Approval is.
A notch at the bearing. Notching the bottom of a beam or header where it sits on a post or jack studs, to get a pipe past, removes wood at the point of highest shear and at the tension face at once. Beam failures at bearings are sudden.
Removing or cutting a jack stud. The jack studs under a header are the header's bearing. Cutting one to pass a duct moves the header's load somewhere it was not designed to go.
Assuming the drywall box is a soffit. A boxed-in beam and a boxed-in duct look the same from below. Before cutting into a ceiling bulkhead, find out which one it is.
References
- International Residential Code, 2021 edition, R502.8.2 (engineered wood products) and R305.1 (basement ceiling height and projections), as adopted by your jurisdiction
- The beam manufacturer's published installation and allowable-hole literature for the specific product, identified from its stamp
- See related: Before You Cut: The Four Things a Hole Can Break
- See related: Engineered I-Joists and the Hole Chart
- See related: The Structural Cut Approval SOP