Is a prefab addition cheaper than stick-built in Ottawa?

Whether a prefab addition costs less than a conventional stick-built one depends heavily on your property. Factory-built modules can save time and some labour, but site preparation, foundation, delivery and on-site finishing narrow the gap, and there is no reliable fixed percentage saving. The only way to know for your house is to price both options against the same scope.

Prefab additions are built in a controlled factory, which offers genuine advantages:

• Weather doesn't delay framing, and factory conditions allow tighter tolerances and air sealing.
• Modules can be built while your foundation is being prepared, then set in place quickly with a crane.
• A shorter on-site phase means less disruption to daily life.

But there are costs unique to prefab:

• Crane delivery and placement. Tight side yards, overhead wires and mature trees can make crane access difficult or impossible, which can rule prefab out entirely. Ask for a site assessment early.
• The foundation is the same. Prefab sits on a conventional foundation. On clay or poorly defined soils, the Building Code calls for footings at least 1.2 m deep and not less than the depth of frost penetration, and on sensitive clay footing sizes must be engineered, whatever is built above.
• The connection to your house. Where the module meets your existing wall, a crew must handle structural connection, waterproofing, air sealing and finishing on site. This junction is critical and is often where hidden costs appear.
• Interior finishing. Some finishing may be left for the site crew after placement. Ask exactly what arrives complete.

Stick-built additions offer more design flexibility. Modules come in standard dimensions that may not match your roofline, window placement or style. For older homes where matching character details matters, a site-built addition lets a contractor replicate trim, cladding and proportions.

Both methods must meet the same Ontario Building Code requirements and go through the same City permit and inspection process. Electrical work needs an ESA notification, and gas work is done by a TSSA-certified gas technician, regardless of where the structure was built.

When comparing, ask each supplier or contractor for an all-in price covering foundation, delivery, crane, connection to the house, mechanical hookups and finishing, so you are comparing totals rather than base module prices. You can browse addition contractors in the Ottawa Construction Network directory at justynrookcontracting.com and compare itemized quotes.

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Looking for experienced contractors? The Ottawa Construction Network connects homeowners with qualified professionals:

• Homeupgraders
• RenoMotion Inc.
• Vanguard Environmental
• L.L. Renovation
• ALTIOR CONSTRUCTION

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