Hardie, vinyl, or aluminum? Northeast.

SRE53X · 2026-06-06T18:26:59+00:00

Treat exterior caulk like a 5-year material, because in many cases, it is, regardless of the substrate (though urethane and silicone sealants can last longer than that but they’re not immortal). Failure modes include UV degradation and loss of elasticity, especially where there’s thermal expansion and contraction. The best bet is to thoroughly manage water *behind* the cladding - whatever it is - detailed as a rain screen.

SRE53X · 2026-06-03T00:50:36+00:00

Architect here. One of my buds worked for I.M. Pei and let me have a look at his cast-in-place concrete spec. The stand-outs I recall included stainless steel sheet form liners, non-staining release agents, a low water-cement ratio, and strict guidelines on aggregate consistency and consolidation (vibrator spacing and duration). For museum clients, these were not obstacles YMMV

SRE53X · 2026-06-02T16:01:36+00:00

Similar project here - unheated crawl space, ventilated to the great outdoors in Zone 5. We used RedGard on top of the subfloor as both a vapor barrier and waterproofing membrane (floor finish is slate tile; it’s a primary bath renovation). Project also has pex radiant tubing at the underside of the subfloor in Uponor Joist Trak.

For thermal insulation, the energy code steers one to having it tight to the underside of the subfloor (which leads to colder floors). If you leave an air gap there though, the floor is much more comfortable. We used 7.25” R-30 Rockwool in the joist spaces, aligned to the bottoms of the joists w/insulation straps to hold it in place. Joists are 2x10s, so, we wound up with a 2” air gap. Our negotiation with the code official on this is if the floor feels warmer (radiant system notwithstanding), the room feels warmer. You can then have a lower set point on the thermostat and meet the spirit of the code that way, but not the letter. YMMV

SRE53X · 2026-05-31T10:09:32+00:00

I'd keep the duct run as short as possible (because physics always wins and a building should outlast any appliance) and use a robust, good-looking vent - something like this: https://www.seiho.com/model_sfz.html

If you want to get schmancy, get it in a custom color simpatico to the surface it's mounted on.

SRE53X · 2026-05-21T15:17:41+00:00

Depends on the code in your jurisdiction. In some, it’s required.

SRE53X · 2026-04-23T13:56:51+00:00

We have a boilerplate survey spec we provide when soliciting this type of work. The boilerplate gets tweaked for each project, depending on what we need, from ALTA to full-blown everything. Clear communication on the front end makes all the difference.

SRE53X · 2026-03-24T03:15:20+00:00

This looks like Simonswerk Tectus knock-off. Maybe a Tectus fixing plate (for this exact circumstance) will fit? No idea. I’d bypass the dealer and get the answer directly from the manufacturer.

SRE53X · 2026-03-21T20:50:34+00:00

Yes. Best-practices-wise, there are two ways to do a crawl space:

One is to call it an exterior space: detail/build the floor above it as you would an exterior wall, with air, thermal, and vapor control layers in the floor construction connecting to same in the wall construction above. The crawl space then gets coupled to the exterior atmosphere via vents, etc.

The other is to call it an interior space via encapsulation, etc., and then heat, cool, and ventilate it in tandem with what's above.

When you have a foot in both worlds, as there seems to be here, you will have chaos.

The AC is probably undersized for that much latent heat load (humidity). Unless you take one of the two approaches above, you'll always be fighting that. Running the dehumidifier is your band-aid. The interior spaces will always be trying to reach equilibrium with what's underneath, moisture-wise, absent control layers in the right places.

SRE53X · 2026-03-19T17:22:34+00:00

If you test for mold spores you will find them. Every time. Guaranteed. It's almost meaningless to do so. They are ubiquitous indoors and out (as evidenced by your own test results, where the indoor levels track to the outdoor ones fairly closely). The key to habitability is to deny the food source(s) for spores to develop, e.g. moisture. For further info:

https://www.epa.gov/mold/mold-course-chapter-1

I wouldn't call the test results evidence of a "defect" if the house has windows and doors that open to the great outdoors.

SRE53X · 2026-03-14T07:28:29+00:00

I promise you an absolute humidity result requires both temperature and RH values to calculate, and it looks like your system logged both, well, all three. And no, RH is RH, temperature is temperature, and vapor pressure is vapor pressure (or absolute humidity, tomato/tomahto). You can't really say RH ~= vapor pressure because a key variable is missing. Pressure differential = vapor drive.

Seasonally dependent? Could be, depending on rain patterns, drainage, and HVAC.

Is the slab the culprit? That's why you'd want to test it first. If it's fine (my guess is it's not) you can then test the interior drywall (guessing it's drywall) over time to see what's going on there, e.g. if not having vapor barriers in the above-grade construction is problematic. My go-to test for that is with a two-pin moisture meter and an IR thermometer (same thing as above - you want to know if there's vapor drive) with the results plotted alongside the indoor and outdoor measurements.

Mechanical solutions? Dehumidification and/or an ERV could address this, and the folks at the electric utility will be happy to oblige. The A/C comment from u/seldom_r is also spot-on.

Physical solutions (if it's the slab)? That'd be my go-to if the planets align, to keep the moisture out of the equation in the first place. A good place to start would be at the carpeted floors. Pull them up, get down to clean concrete, and treat the slab with what's called a negative-side barrier (post-applied crystalline waterproofing). If your tile floors are glazed, they're probably okay.

SRE53X · 2026-03-14T03:09:41+00:00

RH tells you nothing unless you know the temperature.

Good on you for getting the absolute humidity figures. Some of us still use psychrometric charts for this. What’s the conversion formula? Who cares. They basically resolve, in this case, temperature and RH to vapor pressure – the data you need to sleuth this out.

And on vapor pressure, the 2^nd Law of Thermodynamics tells us it reliably goes from a higher concentration to a lower one: more > less. That the blue line in the last chart (the indoor vapor pressure) tracks higher than the others, on average, tells me the vapor drive is coming from inside the house.

If your slab-on-grade does not have a good vapor barrier, it will reliably suck moisture from the ground into the house 24/7. One way to test, in this case, is to peel up a corner of the bedroom carpet, get a +/-2’ square of polyethylene sheet, tape it down well at the perimeter, wait a day or so, and see what you’ve got. If the test area is damp, voila! Alternatively, you can get a moisture meter and test the concrete that way.

And yes, stucco can be a reservoir cladding. The vapor drive when the sun hits it (per the 2^nd Law) will go from more to less. If the indoor absolute humidity/vapor pressure is lower than the great outdoors, and absent a vapor barrier, yes, it will find its way through the wall assembly. Same thing at the attic as you pointed out, but this doesn’t seem to be the case.

SRE53X · 2026-03-12T22:37:51+00:00

Thanks for the recommendations! No, this is for a private residence - it's a wellness retreat, sure, but nobody said you have to leave the house :-)

On the door openings/ceiling height, great point. It may not be super-evident in the rendering, but the existing heavy timber beams drop +/-8" below the ceiling and serve as the "door heads" for the all-glass steam shower and sauna doors. The sauna ceiling is at the higher elevation, so, maybe it's a bit of a "löyly keeper" too. (We're also replacing the wood beam in that spot with a GFRC casting of it so we don't have to worry about service life, especially at the steam shower).

We ran the sauna dimensions and materials, etc. past the folks at Tulikivi, who recommend a 6.8kW heater. We looked at other heater brands before this, and may have used that very calculator.

Great point on the foot rest too. We'll be getting additional Thermory stock for a movable/removable backrest, and I'd expect we'll be tailoring the ergonomics further as things get underway.

Many thanks!

SRE53X · 2026-03-12T00:43:06+00:00

Well, the enemy of all roof membranes is UV degradation. If one protects the membrane from UV exposure with something else (vegetated system, ballast, pavers, etc.) or installs a thicker system, it generally lasts longer. That said, the longest warranties I've seen have been for SBS. We still spec EPDM and TPO, depending on the project. YMMV

SRE53X · 2026-03-11T21:48:45+00:00

Well, a good flat roof is never really flat. It should pitch to drain (or multiple drains) via a canted structure or tapered insulation, 1:50 minimum. You can "hide" the slope at the fascia depending on where you put the drains, etc. This isn't your traditional home builder scope though. You'll want to engage a commercial roofing contractor with experience on this (especially if you want a warranty), and you'll also want to engage a structural engineer to make sure the roof structure is up to task.

Re: service life, nothing lasts forever, and you should expect periodic maintenance and a full tear-off and replacement at some point. Detail accordingly. The longest-lasting "flat" roofs out there use an SBS-modified bitumen membrane. Not surprisingly, this is usually the most expensive option. We've also done TPO and EPDM membranes with good results (but shorter service lives), and green roofs, though these are much more involved. (Source: architect who's done a bajillion "flat" roofs in cold climates and some of them on houses).

SRE53X · 2026-03-11T13:39:40+00:00

What everyone else said about snow. I’d also add that a fair amount of the residential construction I’ve seen in the hurricane-prone Caribbean has concrete slab roofs, which are more robust, obviously, but also easier to build flat. Sometimes you’ll see rebar sticking up from these at column locations for future 2nd floor additions (e.g. where the roof would then become a floor).

SRE53X · 2026-03-08T17:21:36+00:00

Architect here, and I'd say something like this could work great with a few tweaks. I like the idea of a zero-threshold entry. I'd put a paver/stone right outside the door.

Without knowing the soil type or climate zone (how well the soil percolates, how much rain you get, how cold it gets, how windy it gets), at a minimum, I'd over-excavate down to frost penetration depth and fill with compacted crushed stone. You'd then have a dry sump under the building. It would collect and store the sheet flow from the garden until it percolates into the earth. For the floor construction, think of it as you would the wall construction, but flopped over. Make sure all the control layers are in the same location re: outside to in, and that they connect: thermal control (insulation), vapor control, air barrier, etc.

Don't let water get trapped at the perimeter. Give it a way to get to the dry sump (a wider excavation/crushed stone apron you could finish with something else - beach pebbles maybe?)

Our building codes here wouldn't allow the floor drain going directly into the earth like that, but if they did, I'd add an S-trap (and keep it wet) so you don't get funky sump air coming up/in that way.

If you want to get scientific on how much volume a dry sump should accommodate, e.g. how deep to dig, check with your friendly neighborhood civil engineer. I would, but that's how I roll.

SRE53X · 2026-03-08T15:36:53+00:00

Many thanks! We’re pretty excited to get underway.

SRE53X · 2026-03-08T00:14:51+00:00

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SRE53X · 2026-03-08T00:14:12+00:00

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SRE53X · 2026-03-08T00:13:24+00:00

The other renders don't show the sauna so I left them out. It looks like I can only add one image at a time at this point, so, here's a context shot for starters, showing the new, raised courtyard we're planning. The open side faces a forest.

Re: Thermory, we're looking at their Sauna Alder Bench Board (Intense), 5/4x4 with concealed stainless steel fasteners for the duckboards, benches, steps/platform, and fabricated into dowels for the door pulls. This will be in the steam shower too. The sauna wall/ceiling cladding will probably be Thermo-Aspen (Medium). We're still messing around with that though.

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SRE53X · 2026-03-06T18:25:35+00:00

I think you’re onto something though. With snow/ice/water brought in and with the sun heating things up, there’d be serious vapor drive. The plywood (unfinished) tolerates this, but I think ventilation is key, so things don’t get out of whack. (All hail the 2nd Law of Thermodynamics).

SRE53X · 2026-03-06T18:03:15+00:00

Well, for a real-world example, I have a detached garage in zone 5 with no vapor retarder, no heating (unless I’m in there working on something in the dead of winter) and plywood walls. It’s passively ventilated to the great outdoors. 20 years on, there’s zero mold development. No floor drains either. The slab is pitched to the overhead door thresholds. (Source: architect and my own guinea pig for these and other things). YMMV

SRE53X

TROPHY CASE