From a Deck to a Room

Zeke hired PERCH to investigate the possibility of converting a ski condo’s second-floor balcony into an interior space. The floor joists ran parallel to the building façade, meaning the entire deck was ultimately supported by two cantilever beams on the ends. Zeke assumed the cantilever beams were too weak to carry the proposed walls and insulation, and so he needed a low-cost, low-impact plan to retrofit the balcony floor.

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Joist layout of the existing balcony.

Restrictions breed creativity. First, PERCH ordered an investigation of the interior floor system to determine how far back the cantilever beams extended. The property management group drilled a hole in the finish floor and sent a scope camera down the hole, finding that the backspan measured 7 feet. PERCH was able to determine the strength of the cantilever beams accordingly. That provided a baseline for the additional strength required.

I talked over some ideas with Zeke, and wrote a letter to the homeowner describing the most promising options. Here are some of the possibilities I considered…

1. The homeowner could install tall posts to support the balcony floor from ground level. Rejected – not aesthetically pleasing and doesn’t match the other units.

2. The homeowner could hang the balcony from the extended roof. Rejected – this solution would entail far more structural work to investigate the capacity of the rafters and could require a complete roof replacement.

3. The homeowner could build triangle trusses to prop up this floor from new columns running along the house façade. Maybe – it’s simple and fairly unobtrusive, but the visible portions of the structure are not ideal, especially with an exterior stairwell running directly below.

4. The homeowner could reframe the floor so the joists run perpendicular to the façade, and then supported the joists from the interior finish floor via blocking. Yes!

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Blocking layout to effectively create cantilever backspans for the new room (outside the sliding door).

Construction is in progress. Steel joist hangers connect the new room’s floor joists to a ledger board installed against the façade, and blocks reinforce the ledger board from inside.

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New joist configuration and floor insulation.

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