What header size do I need over a 16-foot garage door opening in NB?

A 16-foot garage door opening in New Brunswick typically requires a built-up LVL (laminated veneer lumber) header or an engineered beam sized by a structural engineer, with most installations using a double or triple LVL beam ranging from 1-3/4 x 9-1/4 inches to 1-3/4 x 11-7/8 inches per ply, depending on the loads above. A 16-foot span is well beyond what dimensional lumber can handle safely, so engineered lumber is not optional here — it is the only responsible approach.

The exact header size depends on several factors specific to your garage design and your location within New Brunswick. The two most critical variables are the roof load above the header and the snow load for your community. A garage with just a standard truss roof above the header carries significantly less weight than one with a bonus room, storage loft, or second storey above. In NB, where ground snow loads range from 2.4 to 4.8 kPa depending on your municipality, the header must be sized to carry the accumulated snow load transferred through the roof trusses. A garage in Bathurst or Edmundston with heavy snow loads will likely need a beefier header than one in Saint John or Fredericton.

For a typical single-storey detached garage with standard roof trusses and no storage above, a common solution is a triple 1-3/4 x 9-1/4 inch LVL beam (making a total thickness of 5-1/4 inches) or a double 1-3/4 x 11-7/8 inch LVL beam. For garages with a bonus room or loft above the opening, you may need a triple 1-3/4 x 11-7/8 inch LVL or even a steel beam, particularly in high-snow-load areas of northern NB. The header must bear on properly sized jack studs — typically doubled on each side — with king studs beside them to transfer the load down to the foundation. The bearing points beneath the jack studs must sit on solid framing that runs all the way down to the foundation, not just to the sill plate.

NB Building Code requires that headers for openings this large be engineered. This is not a situation where you can simply look up a span table for dimensional lumber — 16 feet exceeds the practical span for built-up 2x10 or 2x12 headers. Your building permit application will require either an engineering stamp on the header design or reference to the LVL manufacturer's published span tables with the correct load assumptions for your NB location. The materials for a proper LVL header over a 16-foot opening typically cost $200 to $500 in NB, depending on the size and number of plies required.

A practical tip: when ordering your LVL beams, confirm the exact bearing requirements with the manufacturer's span tables or your engineer. Most LVL headers over a 16-foot span need a minimum of 3-1/2 inches of bearing on each side, but many builders provide 6 inches or more for added safety margin. Also, ensure the rough opening is sized correctly for your garage door — a 16-foot door typically requires a 16-foot 2-inch to 16-foot 4-inch rough opening to allow for the door frame and track hardware.

This is a job for a professional framer working from an engineered design. An undersized header over a 16-foot opening can sag under NB snow loads, jamming the garage door, cracking the wall finish above, and potentially creating a structural hazard. Get your header sized properly from the start — it is one of the most important structural elements in any garage with a wide door opening. If you need help finding a qualified garage builder, New Brunswick Garages can match you with local contractors through the New Brunswick Construction Network for free.