Project Profile

A hillside room addition, up into the treetops

A vaulted addition on a steep Transylvania County lot — anchored to bedrock, finished in tongue-and-groove, and open to the woods through a wall of glass.

Location: Transylvania County, NC
Project type: Room addition
Timeline: March – Aug 2026
Contract price: $118,499
Final investment: $143,746

The covered porch at treetop height — black steel posts and railings, blue siding, multi-panel slider visible behind — The covered porch sits at treetop height on the downhill side of the lot.

What they were after

They wanted a room that felt like it belonged in the trees.

This was a second project for a couple in Transylvania County. They knew what they wanted before we started drawing: a dedicated space that connected to the natural setting of their lot — intentional, finished, and theirs.

The lot drops steeply off the back of the house. Their vision was a room that sat above that slope and looked out into the canopy — not a sunroom, not a screened porch, but a real room. Vaulted. With a fireplace. With a view.

The viewA wide opening to the woods. They wanted glass — as much as made sense — facing the slope.
The ceilingVaulted, with wood. They knew they wanted that feeling of height and warmth together.
The fireplaceA gas fireplace on the interior wall for year-round use. Not decorative — something they'd actually light on a cool evening.
The connectionThe new room needed to feel like part of the house, not an attachment. Same roofline language, matching siding.
The porchA covered porch off the addition — so they could sit outside even when it was raining, which in Transylvania County is often.

Footing trench opened alongside the existing house on the hillside, house metal siding visible at left — The slope beside the house, opened for the footing trench.

The completed addition — row of windows, stairs to covered porch, siding matched to the existing house — The same corner, completed — siding matched to the existing house.

How we built it

Starting from the ground up — literally

On a steep hillside lot, you don't get to choose where the foundation goes. The slope dictated a block-wall foundation — excavate down to stable soil, set reinforced footings, build up with block, and pour the slab on top. That foundation is what the entire room sits on, and it's why we contracted a separate engineering scope before framing started.

The framing above it is conventional — walls and a vaulted roof built to carry a metal roof panel system that sheds water and snow cleanly on a steep pitch. ZIP System sheathing wraps it all before the siding goes on: air-sealed, weather-resistant, and ready for nickel-gap hardboard on the walls and a covered porch on the far end.

Building up off a hillside means the foundation does more work than most people expect. We knew that going in.

Foundation trench with rebar in wooden forms before the pour, along the hillside — Reinforcing steel in the footing trench, before the pour.

Mini-excavator cutting the footing trench down the slope alongside the existing house — Excavation on the slope — the footing trench cut from above.

An old Nehi glass soda bottle found in the buried fill during excavation, held in hand — One of the finds from the buried fill — an old glass soda bottle.

The finished interior with multi-panel slider fully open — trees visible, wood ceiling, polished concrete floor — Slider open. The porch and the room read as one space.

What we found underground

The soil changed the foundation plan

When we started excavating for the footings, we hit something unexpected: buried trash. Old fill material — bottles, debris, decades-old dumping — sitting right where the footings needed to go. It's not rare on older rural properties, but it's not something you can predict from the surface or see on a survey.

Soil like that doesn't carry load the way engineered footings require. We brought in a structural engineer to redesign the foundation system — deeper excavation, heavier steel, a different footing configuration — to get down past the fill and into material we could build on.

That redesign added $22,247 to the project. It wasn't in the contract because we couldn't have known it was there. It was in the homeowners' budget because we'd talked about contingencies before we broke ground: on a hillside lot with an older history, something usually comes up.

Rebuilt block foundation walls with Kubota excavator doing crushed stone backfill along the hillside — The rebuilt foundation — block walls reinforced with steel, crushed stone backfilled for drainage.

The finished treetop room interior looking toward the slider, one panel open, trees visible through the glass — The finished room — the glass wall, and the view they were after.

The finished interior from the kitchen side — strip window, wood vaulted ceiling, gas fireplace, opening to kitchen — The new room opens straight into the kitchen, so guests aren't split between two spaces.

A design change along the way

The glass wall got bigger

Once framing was up and they could stand in the room and see the view, they made a call: the original door wasn't going to be enough. They upgraded to a large multi-panel sliding glass door — the kind that nearly disappears into the wall when open. That was $3,000 more than the contracted door, and it's the right call for that room.

The multi-panel sliding glass door viewed from the covered porch — blue siding, four panels, kitchen visible through open panel — The multi-panel slider, set and trimmed, from the porch. Nearly disappears into the wall when open.

The numbers, in full

What this project actually cost

The contract was $118,499. The final was $143,746 — $25,247 more (21%). Almost all of that came from what we found in the ground. Here's every line.

Contract price: $118,499Signed March 2026

Final investment: $143,746$25,247 more than the contract (21%)

What moved it: Foundation redesignEngineer-specified after buried fill was found; plus a door upgrade chosen during the build.

Scope	Amount
Planning, drawings, permits and engineering	$1,366.66
FoundationExcavation, reinforced footings, block walls, drainage, waterproofing, stone backfill, slab, termite treatment	$22,630.69
Concrete floorPolished concrete finish for addition and porch	$6,000.00
Permit fees and soil testing	$600.00
Framing and site protectionWalls, vaulted roof framing, protecting the house during construction	$27,552.42
SidingNickel gap on addition and porch walls	$9,122.42
Roofing	$10,351.72
Walls and ceilingDrywall, tongue-and-groove wood vaulted ceiling	$14,189.66
Trim	$1,277.24
Insulation	$4,827.59
Windows and exterior doors	$5,137.86
Electrical	$14,698.27
Gas lineRelocated existing line and reconnected to new fireplace	$400.00
Landscaping	$344.83
Changes during the build
Engineered foundation redesignAdditional excavation, concrete, steel and block after buried fill was discovered	$22,247.00
Large multi-panel sliding glass doorUpgraded from original door spec — homeowner decision during framing	$3,000.00
Total	$143,746.36

If you're considering a project like this

Hillside lots need honest conversations first

The foundation surprise on this job wasn't surprising to us — it's the kind of thing that happens on steep lots with older histories. What kept this project from becoming a problem was the conversation we had before signing: we told them what we'd seen before, what kinds of things can come up, and what the process looks like when they do.

The homeowners on this project didn't panic when the engineer called. They'd budgeted a contingency, they trusted the process, and they made a good decision on the door because they could afford to. That's the difference between a project that goes well and one that doesn't — and it starts before anyone starts drawing.

On changes during a project: every change on this job — including the foundation redesign — was communicated to the homeowners as it happened, with full information on what it was, what it would cost, and why. Nothing showed up as a surprise on the final invoice. That's how we work, on every project.