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.


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!


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.


New joist configuration and floor insulation.


After Hans and I removed the rotted old decking and built out the new shape of the deck, it was time to install new boards. The roofed portion abuts the back door, a critical spot for moisture protection. We’d managed to pry out the old decking board from the wall without destroying the metal flashing, and we used a flat bar to cram the first new board into the same space. The flashing directs water down the siding and onto the deck, where otherwise it could flow back and get trapped inside the wall.


The first course of new decking slides into the existing flashing.

Our new decking was 1¼-inch-thick untreated pine. We didn’t use pressure-treated lumber because the sawdust is a bit toxic and because this was a budget job; the homeowners will stain the wood later to seal it from the elements. Hans cut lengths to stagger the joints and did a nice job minimizing waste. I mostly stayed on deck and screwed ‘em down.

As we approached the step down and again as we approached the new joists, we started to measure the distance remaining. Our goal was to reach the edge with a full-width decking board, running straight. We tweaked the spaces between boards and finished perfectly on the upper deck. I’m bummed about the lower deck where we finished a hair short, but it looks OK.


Hans cuts new decking to vary the joint location and minimize waste.

The last day was a scramble to finish lots of decking accessories. We built railings from scratch – 18 feet for the new squared-off lower deck plus two 4-foot lengths to create some intimacy on the upper deck (and highlight the step down). We replaced the top rail on all existing railings, cutting rounded ends with a jigsaw to match the shape of the old pieces we scrapped. We leveled the stairs on both sides and screwed new treads on top for equal-height risers. We scribed and cut little pieces of decking to fit around posts where we’d skipped earlier. And we cleaned up as many nails, screws, and wood scraps as we could find.


New railing at the step-down.

A few finishing touches on Saturday morning and the job was done in one week, with plenty of time to spare before the bridal shower.


Isn’t she lovely!


Karen and Neil hired Hans and me to replace their back deck. It had to be complete in time for them to host a bridal shower for their granddaughter, so we worked long days to finish in one week. We worked around weather, taking advantage of a roof over the upper half of the deck to stay dry when it rained.

Step One was to remove the old decking. Happily, the deck was nailed down, not screwed, allowing us to lever the boards out with a massive 5-foot-long pry bar. Most of the boards came out easily, but the unroofed portion of the deck had a lot more rot and the boards were more prone to splitting. I learned to pry free both ends of a board before I tackled the middle. We returned with a regular crowbar to extract any nails that stayed put. The most stubborn ones we lopped off with a sawzall, leaving the tips embedded.

The existing framing was in good shape, so we didn’t need to do much structurally. But we did need to build out the deck’s far end. The old deck wrapped around a pool, and with the pool gone the homeowners wanted to square of the new construction. This was a tricky proposition – how does one lengthen a bunch of variable stringers to the same length, and what new supports are needed?

Hans executed the addition beautifully. First we strung a string along the line we wanted to build to. We dug a trio of postholes four feet deep (frost) and buried 12-foot 4×4 posts in them, holding a level to get the posts perfectly plumb and flush to the string line. Our rim joists went up next, nailed to the outside of the posts. Then I measured each space from old rim joist to new rim joist, along with the angle at one end. Hans cut new joists to match and I toe-nailed them into place, collinear with the existing joists to make the decking easy to attach.


Hans digs a posthole.