How much does it cost to add extra support posts under a Calgary deck to stop the bounce in the middle?

Adding support posts to eliminate deck bounce typically costs $800-$2,500 in Calgary, depending on the number of posts needed, footing requirements, and access conditions. Most bouncy decks need 2-4 additional posts with proper footings to achieve adequate support.

The bounce you're feeling indicates that your deck joists are spanning too far without intermediate support, or the existing beam structure is undersized for the load. This is a common issue with older decks built to less stringent standards, or DIY decks where proper beam sizing wasn't calculated. The solution involves installing additional support posts with concrete footings that extend below Calgary's 1.2-metre frost line.

Cost breakdown for additional support posts:

• Single support post with footing: $400-$800 installed (includes excavation, sonotube, concrete, pressure-treated post, and beam connection)


• Two posts with beam: $800-$1,500 (most common solution for bouncy decks)


• Three or four posts: $1,200-$2,500 depending on spacing and beam requirements

The exact number of posts depends on your deck's current joist span and beam layout. Most deck joists should span no more than 12-16 feet without intermediate support, depending on the joist size and spacing. If your joists are spanning 16-20 feet or more, that explains the bounce. Adding a beam supported by posts at the midspan point typically eliminates the problem entirely.

Calgary-specific considerations make this more complex than in other cities. Every new footing must extend at least 4 feet below grade to prevent frost heave during chinook freeze-thaw cycles. Shallow footings will shift and lift, potentially making the bounce worse over time. The posts themselves need proper galvanized hardware connections to resist Calgary's extreme temperature cycling, and the beam-to-post connection must be engineered to handle both vertical loads and lateral movement from wind and thermal expansion.

Access and timing affect the cost significantly. If your deck is elevated and the area underneath is accessible, installation is straightforward. If the deck is close to grade or surrounded by landscaping, excavation becomes more difficult and expensive. The work should be done during Calgary's building season (May through October) when the ground isn't frozen and concrete can cure properly.

This is definitely professional work requiring a structural assessment. A qualified deck contractor needs to evaluate your existing joist spans, beam sizes, and load paths to determine exactly where support posts should be placed. Simply adding posts randomly won't solve the problem and may create new stress points. The contractor will also need to verify that the existing ledger board connection to your house can handle the redistributed loads.

Signs you need immediate professional attention: If the bounce is severe (more than 5mm deflection when walking), if you hear creaking or cracking sounds, or if you notice any separation between the deck and house, stop using the deck until it's professionally evaluated. Bouncy decks can indicate serious structural deficiencies that may lead to collapse if not addressed properly.

Need help finding a deck contractor experienced with structural repairs? Calgary Deck Contractors can match you with professionals who understand Calgary's unique footing and structural requirements for a free assessment of your bouncy deck situation.

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

• The Original Workshop
• Venkor Group Inc
• Upper Cut Landscaping LTD
• Dealtwith.
• WestAim Construction Ltd.

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