You found a plan online. It’s $1,800, it looks close to what you want, and the alternative is a custom design process that costs meaningfully more. It seems like an easy call.
Sometimes it is. But the savings are smaller than they look, and in Teton Valley there’s a specific reason that catches almost everyone.
The three paths
- Stock plan as-is. Buy a plan set from a plan house or designer and build it unchanged. Typically $1,000 to $2,500 for the set.
- Modified stock plan. Buy the set, then pay a designer to change it — move walls, resize the garage, flip the plan, redo the primary suite. Modification services commonly run $2,000 to $8,000 depending on how far you go.
- Fully custom. Designed from your lot, your program, and your sun and view angles. Sold as a design agreement with a fixed fee, quoted per project.
On paper the spread between path one and path three looks enormous. Then you go get a permit.
The catch: an online plan isn’t permit-ready here
Stock plans are drawn for a generic location and generic conditions. Teton Valley is neither. What a purchased plan set almost never includes, and what you will pay for regardless of which path you choose:
- Snow load engineering. We design to 60 to 100+ psf depending on where you are. A plan drawn for 30 psf has undersized rafters, beams, headers, and connections throughout. That isn’t a tweak — the structural design gets redone.
- A local engineer’s stamp. Required. The engineer stamping it has to actually engineer it, which means running the loads for your site.
- Foundation redesign for frost depth and your soils. Footing depth, frost walls, and what the soils report says about bearing. A slab detail from a warm climate is not transferable.
- Energy code compliance for this climate zone — assemblies, glazing ratios, and the compliance documentation.
- Site-specific plot plan — setbacks, septic and well separation, drainage, snow storage.
- Seismic and wind per the adopted code in your jurisdiction. Adopted codes by county.
Once you’ve paid for all of that, the real gap between a modified stock plan and a fully custom design is a lot narrower than the sticker suggested. You didn’t skip the engineering — you just bought the floor plan separately from it. What a plan set actually needs to contain here.
Does a stock plan lower construction cost?
Not by itself. Construction cost is driven by what’s in the drawing, not by who drew it.
The cost drivers, in rough order of impact:
- Footprint complexity. Corners cost money. A simple rectangle frames faster, roofs cleaner, and leaks less than the same square footage broken into six bump-outs.
- Roof geometry. Valleys, dormers, and intersecting pitches are the single most expensive thing on most plans — in labor, in flashing, and in snow country, in risk.
- Structural spans and open volume. Great rooms with long clear spans and vaulted ceilings need engineered beams and specific floor and roof systems. TJI vs floor trusses.
- Foundation type and site. Walkout basement on a slope versus slab on flat ground is a large swing.
- Finish level. Two identical plans can differ by 40% on finishes alone.
- Window and glass area. The views you came here for are the most expensive wall assembly on the house.
Where a stock plan does save construction money is indirect and real: plan houses sell what builds efficiently, so their plans tend to have simpler forms and standard dimensions. A custom design can absolutely be drawn that way too — a good designer working against a budget will — but a plan nobody constrained will happily produce a shape that costs 15% more to frame for no functional gain. More on what drives cost per square foot.
How much control do you actually get?
| Stock as-is | Modified stock | Fully custom | |
|---|---|---|---|
| Floor plan layout | Fixed | Substantial control | Total |
| Orientation to views and sun | Whatever the lot allows | Can flip and rotate | Designed around it |
| Exterior style and materials | Limited | Good | Total |
| Ceiling heights and volume | Fixed | Possible, costs engineering | Total |
| Window sizes and placement | Fixed | Good | Total |
| Finishes, fixtures, cabinetry | Total | Total | Total |
| Fit to an odd or steep lot | Poor | Limited | Total |
Note the bottom two rows. Finishes are fully yours on every path — that’s the part most people picture when they say “custom,” and it’s never the constraint. The constraint is the lot.
When a stock or modified plan is the right call
- Your lot is flat, rectangular, serviced, and doesn’t have one dominant view you’re organizing around.
- You found a plan that genuinely fits how you live, and the changes you want are modest.
- Budget is tight enough that design fee is the difference between building and not building.
- You want to move quickly and a design process would add months to your start.
- It’s not your forever house.
When fully custom earns it
- The lot is the reason you’re building here. Slope, a specific Teton view corridor, tree cover, or an awkward shape. A stock plan dropped on a view lot usually points the great room at the neighbor.
- You have a specific program. Multi-generational living, a real home office for someone who works from it every day, a mudroom sized for four kids and ski gear.
- Solar orientation and snow shedding matter to you. Where the sun hits in January and where the roof dumps snow relative to your doors and driveway are design decisions. Stock plans make them by accident.
- You’re at the top of this market. At the price point where buyers compare finish and design quality directly, a recognizable stock plan is a resale liability.
- You want the price to be real before you commit. A design process that ends in complete drawings and a finish specification is what makes a fixed construction price possible at all. How to get a real number before you sign.
The honest recommendation
For most people building a forever home on a Teton Valley lot they chose for the view, a modified stock plan is a false economy — you spend most of the design savings on engineering and modifications and still end up with a house that doesn’t quite fit the site.
For a flat lot, a straightforward program, and a budget that’s actually tight, a well-chosen plan modified by a designer who understands our snow loads is a perfectly good answer, and I’ll build it.
What I’d avoid entirely: buying a plan online, handing it to a builder, and assuming it’s ready to go. That is the version that costs money twice. How the design agreement works.
Frequently asked questions
What’s the price difference between stock plans and a fully custom home?
A stock plan set typically runs $1,000 to $2,500, and modification services commonly add $2,000 to $8,000. Fully custom design is sold as a design agreement with a fixed fee quoted per project. The gap looks large until you add the structural engineering, stamped drawings, foundation redesign, and energy code documentation that a purchased plan does not include and that every path requires.
Can you build a stock house plan in Teton Valley?
Not as purchased. Stock plans are drawn for generic conditions and Teton Valley requires 60 to 100+ psf snow load design, a local engineer’s stamp, foundation design for frost depth and site soils, energy code compliance for this climate zone, and a site-specific plot plan addressing setbacks, well and septic separation, drainage, and snow storage. The structural design is effectively redone.
Does using a stock plan lower construction cost?
Not directly — construction cost is driven by what is in the drawing, not by who drew it. Footprint complexity, roof geometry, structural spans, foundation type, finish level, and glass area are the real drivers. Stock plans do tend toward simpler forms and standard dimensions because plan houses sell what builds efficiently, which can help. A custom design drawn against a budget achieves the same thing.
How much control do you have over the design of a custom home?
Total control over layout, orientation, ceiling volume, window placement, exterior style, and fit to the lot. Worth knowing that finishes, fixtures, and cabinetry are fully yours on every path including a stock plan — that is the part most people picture when they say custom, and it is never the constraint. The constraint is the lot and the floor plan.
When is a modified stock plan the right choice?
When the lot is flat, rectangular, and serviced without one dominant view to organize around; when you have found a plan that genuinely fits how you live and the changes are modest; when the design fee is the difference between building and not building; when speed to start matters; or when it is not your forever home. On a view lot or a sloped lot, a stock plan usually ends up pointing the main living space in the wrong direction.
Send me the plan you found
Book a 15-minute planning call with the plan and your lot. I’ll tell you what it needs to be buildable here, and whether modifying it or starting fresh is the better use of your money.
— Bryce Swager, owner and lead builder, SwagerBuilds. Rigby, Idaho.