Do I need steel beams or can I use engineered wood for my Ottawa addition?

The choice between steel beams and engineered wood is one of the bigger structural decisions in an Ottawa home addition. Both are accepted under the Ontario Building Code (OBC) when properly designed, but each brings different strengths, costs and practical considerations.

Engineered wood products such as LVL (laminated veneer lumber), PSL (parallel strand lumber) and glulam beams handle many residential addition spans well. For a typical single-storey addition with a moderate opening, a properly sized built-up LVL beam is often enough, and it is much easier to work with than steel. It arrives on a regular lumber truck, can be carried in by hand or with modest equipment, and goes up with ordinary framing tools.

Steel tends to win when spans get longer or loads get heavier. If your design calls for a wide open space without intermediate posts, or you are removing a load-bearing wall to join the addition to the existing house, a steel beam can carry the load in a much shallower profile. That can be the difference between a flush ceiling and a beam that drops into the room. For second-storey work, where a beam may carry a new floor, walls and roof above, steel at the transition point is common.

Whatever the beam, the load has to come down somewhere. Heavy beams create concentrated point loads on posts and footings, so the footings at those bearing points must be designed for them. Footings in clay or soils that aren't clearly defined must be at least 1.2 m deep and not less than the depth of frost penetration. On filled ground, peat or sensitive clay, including Leda clay, the Code requires the footing sizes to be engineered. Ask your engineer to confirm what your soil means for the posts.

On site, engineered wood is easier to modify. A framing crew can cut, drill and fasten to LVL with standard tools and hardware. Steel usually needs a crane or boom truck for placement, specialized connectors or welding, and pre-planned holes for any penetrations. On tight lots in older neighbourhoods, simply getting a long steel beam into position can be a real logistical job, so ask how the contractor plans to deliver and set it, and whether that is priced into the quote.

Fire protection is another consideration. Steel loses strength at high temperatures and is often enclosed in drywall where fire protection is required. Large engineered wood members char on the outside, which slows the loss of strength in the core. Your designer will confirm what protection, if any, your layout needs.

In the end, your structural engineer or designer specifies the material based on your actual spans, loads and soil conditions. Check with the City's Building Code Services for what drawings your permit needs, then ask contractors for itemized quotes that show the beam, posts and footings as separate lines.

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• L.L. Renovation