Attaching an Attached DIY Timber Frame Pergola Kit Over a Deck

A 40-Foot Pergola That Had to Clear the Roofline

The Hilton family in Orem, Utah came to us with a good problem. They had an open second-story deck they loved — and wanted more of it: more room, and some shade overhead, without boxing in the tall windows or the view.

The catch was the roofline. They wanted an attached pergola kit that ran the full length of the deck and sloped back toward the house — which meant the pergola’s own roof had to clear the home’s existing roof. Here’s the deck before, and after.

BEFORE

AFTER

The design challenge: a roof that had to miss a roof

The whole structure hangs off the house through a ledger — a heavy board fastened to the wall that carries part of the roof’s weight. On this project, the ledger’s height wasn’t just a fastening detail; it set the slope of the entire pergola. Our design and engineering team had to place that ledger high enough, and pitch the roof just right, so the sloped structure cleared the home’s existing roofline instead of running into it. It’s the kind of problem that looks invisible once it’s solved — which is exactly the point.

Pre-cut to the inch — so layout is everything

Every timber in this pergola was designed, then CNC-cut and stained at our shop before the crew ever arrived in Orem. That’s what lets a kit go up quickly — but it also means there’s no fudging on site. The longest part of the install isn’t raising the timbers; it’s the layout: getting the post placements exactly right, since they’re permanent, and setting the ledger at precisely the height the plans call for. Hit those marks and the pre-made pieces drop together. Miss them, and pre-cut timber won’t forgive you — so the crew measures, checks, and measures again before anything is anchored. It starts with the wood itself: Western Timber Frame buys #1-or-better Douglas Fir before any beam is cut.

How the frame locks together

Once the posts are standing, the main support beams drop in and interlock using our patented Dovetail Difference® joinery — a wood-to-wood connection that carries the load on its own. A couple of lags go in at the top as added insurance, and knee braces tuck in underneath for extra support, but the dovetail is what’s really doing the work. No exposed bolt hardware, no rattle, no gradual loosening season to season.

Shade over the whole deck, without losing the light

The finished pergola runs a full 12′ × 40′ along the back of the house, its open-slat roof laying dappled shade across the deck while keeping the tall windows bright and the view wide open. It’s finished in Early American, a warm, UV-protected timber stain that reads rich against the stucco. And because it’s real timber — which conducts heat far more slowly than metal — the beams stay comfortable overhead instead of radiating the afternoon sun back down onto the deck.

Western Timber Frame has built more than 7,000 timber structures since 2008, engineered to code in all 50 states. This one took a design manager on site, a full design and engineering team, a 3D rendering before a single cut, and a shop full of pre-made timber to pull off — and it went up clean, roofline and all. That work has earned 28 Best of State awards.