Mountain Home Cabinetry
Altitude and Moisture
The dry extreme in a heated Sierra house is January, not July. What the climate normals say, how far the wood follows the air, and what that does to a 24-inch panel.
Quick Answer
What does altitude do to cabinet moisture?
Nothing directly. What matters is the long, cold winter that comes with it — a January mean of 30.1 degrees at Tahoe City in the NOAA normals — and the furnace running against it. Warming that air dries it sharply, so the dry extreme for cabinetry in a heated Sierra house is winter, not summer.
The Wood Handbook puts the consequence in one row: at 70 degrees Fahrenheit, wood settles at 9.2 percent moisture content in 50 percent relative humidity, 6.2 percent at 30 percent and 4.5 percent at 20 percent. Over a three-point swing a 24-inch flat-sawn white oak panel changes about a quarter inch in width; quartersawn, about an eighth.
Key Takeaways
- The NOAA normals describe a cold, long winter: a January mean of 30.1 degrees and 37.9 inches of normal January snow at Tahoe City; 28.9 degrees and 43.6 inches at Truckee. Measurable normal snowfall runs October through May.
- The Forest Products Laboratory states that moisture requirements are more exacting inside heated buildings, and that wood indoors in northern climates loses moisture in winter and gains it in summer — the reverse of wood outdoors.
- At 70 degrees Fahrenheit the Wood Handbook puts equilibrium moisture content at 9.2 percent in 50 percent relative humidity, 6.2 percent at 30 percent and 4.5 percent at 20 percent. Temperature barely shifts those values across the indoor range.
- A three-point winter swing moves a 24-inch flat-sawn white oak panel about 0.26 inch; quartersawn, about 0.13. Red alder and cherry move about 0.18 flat-sawn. These are averages with roughly 15 percent variability between pieces.
- The published coefficients cover 6 to 14 percent moisture content. A heated house at 20 percent relative humidity takes wood below that range, which is an argument for wider clearances and for veneer-core panels where width or a clear finish demands it.
What the Climate Normals Say About Tahoe City and Truckee
The useful description of a mountain climate for a cabinetmaker is not the elevation but the thirty-year averages, because they say how cold the air outside the house is and for how long.
NOAA’s 1991–2020 climate normals for the Tahoe City cooperative station, which sits at 1,898.9 metres — about 6,230 feet — give a January mean temperature of 30.1 degrees Fahrenheit, a January mean minimum of 20.6, and a July mean of 62.0 with a mean maximum of 78.0. Normal snowfall is 37.9 inches in January, 41.3 in February, 34.7 in March and 36.2 in December, and normal precipitation runs from 6.21 inches in January to 0.17 in July. The Truckee ranger station, at 1,774.9 metres, is colder in winter and warmer in summer: a January mean of 28.9 degrees with a mean minimum of 16.1, a December mean minimum of 15.0, a July mean maximum of 83.8, and normal snowfall of 43.6, 47.9 and 44.2 inches in January, February and December.
Two things in those rows matter for cabinetry. The first is that the outdoor air is below freezing on an average January night at both stations, and stays cold for a long season — Tahoe City records measurable normal snowfall from October through May. The second is that the summer is genuinely dry: 0.17 inches of normal July precipitation at Tahoe City and 0.26 at Truckee. A Sierra house does not have a humid season the way a coastal one does. It has a cold season and a dry season, and the interior is dry through both for different reasons.
Why Does a Heated Mountain House Run So Dry?
Relative humidity is relative to temperature. Air that is nearly saturated at 20 degrees holds very little water, and when it is drawn indoors and warmed to 70 with nothing added, the same small quantity of vapour is spread across a much larger capacity.
That is the whole mechanism, and it is why the Forest Products Laboratory states that moisture content requirements are more exacting for finished lumber and wood products used inside heated and air-conditioned buildings than for lumber used outdoors or in unheated buildings. The Wood Handbook adds the seasonal shape for cold-winter regions: wood indoors in northern climates increases in moisture content during the summer and decreases during the winter, the reverse of wood outdoors, which gains moisture in winter and loses it in summer. A Tahoe or Truckee house is a northern-climate interior in that sense, whatever its latitude.
How dry the room actually gets is not something this guide will put a number on, because it depends on the house. The Wood Handbook says the in-service moisture content of interior wood primarily depends on indoor relative humidity, which in turn is a complex function of moisture sources, ventilation rate, dehumidification and outdoor humidity conditions. A tightly built house with a humidifier, a family cooking three meals a day and a dog is a different interior from a leaky cabin with forced-air heat and nobody home. What can be said is the direction — drier than the valley, drier than the coast — and that the furnace runs for the months the normals describe.
The companion guide on wood movement works through the equilibrium curve in general terms. The point for the mountains is which part of the curve the house lives on. The Forest Products Laboratory recommends installing interior woodwork and furniture at an average of 8 percent moisture content across most of the United States, 6 percent in the dry southwestern area and 11 percent in the damp warm coastal area, with individual pieces held to 6 to 10, 4 to 9 and 8 to 13 percent respectively. It also notes that hardwood lumber for furniture, cabinets and millwork is usually dried to 6 to 8 percent. A heated Sierra interior in January is, in practice, asking the wood to go below the bottom of the general range.
How Far Does the Wood Actually Follow the Air?
The Wood Handbook tabulates equilibrium moisture content against temperature and relative humidity. Reading the 70-degree row is the single most useful thing a mountain homeowner can do with it.
At 70 degrees Fahrenheit, wood settles at about 2.5 percent moisture content in 10 percent relative humidity, 4.5 percent at 20 percent, 6.2 percent at 30 percent, 7.7 percent at 40 percent, 9.2 percent at 50 percent, 11.0 percent at 60 percent and 13.1 percent at 70 percent. Read it from the summer end: a house at 50 percent in July and 30 percent in January moves its cabinetry across three points of moisture content. A house that drops to 20 percent in a cold snap with the furnace running moves it nearly five. The curve is not linear — it is flatter at the dry end and steepens sharply above 70 percent — which is why the dry end of the range is less dramatic per point but still adds up across a wide panel.
The values carry two caveats the Wood Handbook states and this guide repeats. They were derived primarily for Sitka spruce under oscillating vapour-pressure desorption and are applied to other species as a practical approximation. And wood shows sorption hysteresis: a piece arriving at a given humidity from the wet side settles higher than one arriving from the dry side, at a ratio averaging about 0.8 near room temperature. A door that dried down through a winter and a door that wetted up through a summer can sit in the same room at different moisture contents.
Temperature itself barely changes the picture inside a house. The same table gives 4.6 percent at 20 percent relative humidity and 6.3 percent at 30 percent for 30-degree air — within a tenth of a point of the 70-degree values. That matters for the closed-up, unheated second home: what its wood does is governed by the relative humidity of the cold interior, not by the cold itself. The guide on seasonal occupancy takes that case up in detail.
| Relative humidity | EMC at 70 °F (heated house) | EMC at 30 °F (unheated house) | What it means for cabinetry |
|---|---|---|---|
| 20% | 4.5% | 4.6% | Below the 6 to 14 percent band the dimensional-change coefficients are published for. A heated house in a cold snap can reach it. |
| 30% | 6.2% | 6.3% | The bottom of the Forest Products Laboratory’s recommended installation range for interior woodwork in most of the United States. |
| 40% | 7.7% | 7.9% | Near the 6 to 8 percent the Wood Handbook says hardwood lumber for furniture, cabinets and millwork is usually dried to. |
| 50% | 9.2% | 9.5% | A comfortable summer interior with the windows open; the top of the recommended 6 to 10 percent range for individual pieces. |
| 70% | 13.1% | 13.5% | Unlikely in a heated house; plausible in a closed-up, unheated one during a wet winter or spring. |
| 80% | 16.0% | 16.5% | Beyond anything a conditioned interior should reach. Shown to make the point that the curve steepens sharply at the top. |
What a Three-Point Winter Swing Does to a Door
The Forest Products Laboratory publishes dimensional-change coefficients for the 6 to 14 percent moisture content range, and the arithmetic is one line: starting width, times the coefficient, times the change in moisture content.
Take a 24-inch-wide solid panel — the width of a generous pantry door — and move it from 9.2 percent to 6.2 percent, the 50-to-30-percent-humidity swing. Flat-sawn, the tangential coefficient applies. Red alder, at 0.00256, changes about 0.18 inch, a little under three-sixteenths. Black cherry, at 0.00248, changes about 0.18 inch. Coast-type Douglas-fir, at 0.00267, about 0.19. Black walnut, at 0.00274, about 0.20. Commercial white oak, at 0.00365, about 0.26 inch — just over a quarter. Quartersawn, the radial coefficient applies instead: 0.00151 for alder gives 0.11 inch, 0.00126 for cherry gives 0.09, 0.00165 for Douglas-fir gives 0.12, 0.00190 for walnut gives 0.14, and 0.00180 for white oak gives 0.13. The oak panel that moved a quarter inch flat-sawn moves an eighth quartersawn.
Those figures are averages, and the Wood Handbook is plain about what that means: the variability of transverse and volumetric shrinkage runs to a coefficient of variation of approximately 15 percent, and predicting the shrinkage of an individual piece is impossible, while the average of a quantity can be predicted accurately. The published coefficient is a design allowance. A panel groove cut to exactly the arithmetic is a panel groove that will bind on the one board in seven that moves more than average.
There is a second caveat that is specific to the mountains. The coefficients are published for 6 to 14 percent, and the Wood Handbook says the arithmetic is used when moisture content remains within that range. A heated house at 20 percent relative humidity takes wood to about 4.5 percent, below the range. The honest statement is not that the wood stops moving there, but that the published numbers no longer describe it precisely — which is one more reason to give a panel more clearance than the calculation strictly demands, and to prefer construction that does not depend on the calculation at all.
What the Shop Does With These Numbers
None of the figures above argue for a special mountain cabinet. They argue for ordinary good construction with the margins set wider and the exceptions removed.
The first decision is cut. For white oak the tangential-to-radial ratio is about two to one, so specifying rift- or quartersawn stock roughly halves the seasonal width change of every solid component — the strongest single lever available, and the reason the Architectural Woodwork Standards require the method of slicing to be specified for wood casework rather than left to the shop. For walnut and cherry the ratio is flatter and the absolute movement lower, so flat-sawn stock is defensible in narrower components and the cut can be chosen for figure.
The second is where solid wood stops. The Architectural Woodwork Standards permit solid lumber raised panels only up to a width limit and require a rim raised panel — veneer over a stable panel product — for Premium grade, whenever that width is exceeded, and whenever a transparent finish is used. In a dry house the sensible reading of that rule is conservative: wide panels, and any panel behind a clear finish where a shrinkage line would show, go to a veneer-core construction whose cross-banded plies restrain movement in both directions. The panel then changes dimension by a small fraction of what the solid arithmetic predicts.
The third is clearance and restraint. Solid panels float in grooves with room at the edges, glued at most at the centre of the top and bottom rails so movement is shared to both sides, exactly as the Forest Products Laboratory describes for interior finish work: design and install large solid pieces so that the panels are free to move across the grain, and prefer narrow widths. Face frames, stiles and rails are narrow with their length along the grain, where longitudinal shrinkage runs only 0.1 to 0.2 percent green to oven-dry, so they hold the door’s shape while the panel does the moving. And the whole assembly is finished on all faces before delivery and brought into the conditioned house to settle before it is hung — the Wood Handbook’s instruction to install wood at the moisture content it will experience in service, applied to a house that has two.
Frequently Asked Questions
- How dry does a heated Tahoe or Truckee house get in winter?
- Drier than the valley, and this guide deliberately does not put a number on it, because the Wood Handbook says indoor relative humidity is a complex function of moisture sources, ventilation, dehumidification and outdoor conditions — in other words, of the particular house. What is certain is the direction: outdoor air that the NOAA normals put at a January mean of 30.1 degrees at Tahoe City holds very little vapour, and warming it to room temperature drops its relative humidity sharply.
- What moisture content will my cabinetry reach in a dry winter interior?
- At 70 degrees Fahrenheit the Wood Handbook puts equilibrium moisture content at 6.2 percent in 30 percent relative humidity, 4.5 percent at 20 percent and 2.5 percent at 10 percent, against 9.2 percent at 50 percent. The Forest Products Laboratory recommends installing interior woodwork at an average of 8 percent in most of the United States and 6 percent in the dry southwestern area; a heated Sierra house in January can push below the bottom of the general range.
- How much does a solid door panel move over a Sierra winter?
- Using the Forest Products Laboratory coefficients and a three-point swing from 9.2 to 6.2 percent moisture content, a 24-inch flat-sawn white oak panel changes about 0.26 inch in width and the same panel quartersawn about 0.13; flat-sawn red alder about 0.18 and quartersawn about 0.11; cherry about 0.18 and 0.09. The Wood Handbook puts the variability of individual pieces at a coefficient of variation of roughly 15 percent, so these are allowances, not predictions.
- Does altitude itself do anything to wood?
- No. Wood responds to temperature and relative humidity, and the Wood Handbook’s equilibrium table shows that temperature barely matters across the indoor range — 6.2 percent at 30 percent relative humidity and 70 degrees against 6.3 percent at 30 degrees. What altitude brings is the climate: a long cold season outside, from which the Forest Products Laboratory’s statement about heated buildings and northern-climate interiors follows.
- Is quartersawn white oak worth specifying for a mountain kitchen?
- For wide solid components, yes, and on the numbers rather than the look. Commercial white oak carries a tangential coefficient of 0.00365 and a radial coefficient of 0.00180 per 1 percent change in moisture content, so a quartersawn panel moves roughly half as much across its width as a flat-sawn one. The Architectural Woodwork Standards require the method of slicing to be specified for wood casework, which is the mechanism for asking.
- Why do my cabinet doors look different in February than in August?
- Because the Forest Products Laboratory’s description of a northern-climate interior applies: wood indoors decreases in moisture content during the winter and increases during the summer. A floating solid panel shrinks across its width in winter and can expose a thin unfinished line at its edge; that is the panel working as designed. A panel glued rigidly into its frame would have cracked or pushed the joints open instead.
References
- USDA Forest Products Laboratory — Wood Handbook: Wood as an Engineering Material, FPL-GTR-190 (2010). Table 4–2 (equilibrium moisture content), Table 13–2 (recommended moisture content at installation), Table 13–5 (dimensional change coefficients), Chapter 13 (Recommended Moisture Content), Chapter 16.
- NOAA National Centers for Environmental Information — U.S. Climate Normals 1991–2020, monthly, stations USC00048758 (Tahoe City, CA; elevation 1,898.9 m) and USC00049043 (Truckee RS, CA; elevation 1,774.9 m).
- NOAA NCEI — U.S. Climate Normals (product page).
- Architectural Woodwork Institute — Architectural Woodwork Standards (method of slicing; solid lumber and rim raised panel requirements).
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Moisture Is the First Constraint, Not the Only One
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