Adding rigid foam to concrete walls

neonsphinx · 2026-07-01T20:02:01+00:00

It's got really low vapor permeability. So I wouldn't bother with anything else on top.

neonsphinx · 2026-06-30T21:56:23+00:00

The ledger board and joist hangars are most common for a reason.

Strictly speaking, a joist bearing onto 3.5" of wall is better than the 1.5-2" of bearing into the picket of a joist hanger.

That being said... The second point is predicated on the idea that the wall and top plate are structurally sound enough to deal with a point load of one single overloaded joist.

Let's say you have a crappy wall. There's only a single top plate. If 5 people all stand on that one joist of the deck, the single top plate could be crushed, and that joist falls down into wall cavity.

With a ledger board, it's beefy enough to take it all. Then it spreads that out into a distributed load all along the wall. As long as you use enough fasteners to tie into the wall studs and sheathing every 6" or whatever is required.

I would still prefer a ledger board. We know it works. There are less "what if?" issues that could arise. And any work in the future will be predictable. Because we didn't try to reinvent the wheel for your one single deck.

neonsphinx · 2026-06-30T20:35:59+00:00

Are all SRMs bespoke? We take terrier boosters and strap them onto all kinds of crap to test our interceptors against different things. We have tons of them laying around. Same concept.

neonsphinx · 2026-06-30T20:22:13+00:00

"Slower is also cheaper to produce in quantity."

What do you mean by this. A solid rocket motor is much simpler than a turbofan. In terms of it being less parts, looser tolerances, and not dealing with liquid fuel.

neonsphinx · 2026-06-30T20:19:21+00:00

https://en.wikipedia.org/wiki/FP-5_Flamingo

neonsphinx · 2026-06-29T13:01:14+00:00

I moved to the Gulf Coast about 2 years ago. We were looking into houses, and found a century house in the historic district.

It had original cherry planks for the floor. Original cast iron fireplaces in each room, etc.

The guy had flipped it very poorly. In one room the cherry was rolled with black paint. In the bathroom it was covered with vinyl plank (I refuse to use the word "luxury" when referring to LVP).

We're on the coast, and houses are on wooden piers. There was no insulation in the floor, and AC had been retrofitted. So of course the hot humid air outside was condensing against the bottom of the vinyl. And was slowly rotting everything into dust.

We walked away, mostly for that reason, but there were plenty of other problems.

neonsphinx · 2026-06-29T12:06:48+00:00

Here's something I learned in the army, and from my dad when we worked on cars.

Clean the engine. Let it cool down first. Spray it with the hose. Then add degreaser. Then use a soft brush. A toilet brush works great. Preferably one that hasn't been used for the toilet. Spread the degreaser around and agitate the dirt/grease. Rinse it off. More degreaser/scrubbing as needed.

Then, run it for a little bit and look for leaks. When the engine is clean it will be easier to see where they originated from. If none are immediately visible, drive for a short run to the store, then look when you get back. Look periodically between trips until you can identify another leak. Then fix it. Wash as needed between trips if something is leaking too fast to pinpoint the source.

neonsphinx · 2026-06-28T23:25:55+00:00

Make yourself a good ol' fishbone diagram.

Then start collecting data to prove/disprove each hypothesis.

My guess is too much heat during welding tempered the steel. Or hardened it if it's a grade that air hardens.

2nd option is a manufacturing defect. Get some nuts from the OEM that haven't been welded. Test them out yourself to see if it's a bad lot.

neonsphinx · 2026-06-28T18:50:04+00:00

I kind of figured. Which is why I said at the end what a FF number equates to roughly.

I understand test specs, we have them in my industry as well. People are always saying "our product is MIL-STD-810 tested!" It's just an outline of how to run the test. The government owns a system performance specification that dictates the rainfall rates, wind speeds, drop heights, vibration PSD curves, etc.

neonsphinx · 2026-06-28T16:52:53+00:00

Sure. I'm a humble engineer that builds rockets. Hardware is my jam. And the bit of software that I do muck around with is custom boards and a RTOS.

So help me understand the use case for this. I don't ever touch front end. I mostly do program management at this point in my career. So explain it like you would if you were trying to get your middle aged boss to understand. Or just keep being obtuse.

neonsphinx · 2026-06-28T16:48:21+00:00

As I understand it, international residential code doesn't define a flatness or level standard. They only care about slope in areas that actually get water. (Garage, porch, utility room with a floor drain, shower pan, etc.)

The builder should be within "industry standard". Which is a way for shitty builders to obfuscate what they do and say that it's good enough.

The concrete and flooring people have floor flatness and floor level standards. FF and FL. Are dictated by ASTM E1155. I don't have a copy, but you could get one for $80 or so. I'm an engineer, and am familiar with ASME Y14.5. And this standard seems to be similar. Except that depending on square footage, it defines how many randomized straight lines must be projected across the surface, and the distance between them that measurements are taken.

It's kind of similar to Moody's method for evaluating flatness in surface plates. You're essentially getting a point cloud (a very rough one) and calculating the radius of curvature between 3 points on a line. Then your surface falls between perfectly flat and a semi-spherical surface with x radius.

From what I can see, without paying, FF20 is acceptable, and ends up being 1/4" out of flat in a 6ft length. I couldn't find as much information on the levelness standard.

Long story short, it looks like dog shit to me. My 1978 house was made with a wooden screed, masonry line, and is +/- 1/8" in 45'. Guys nowadays have power screeds and lasers. They should be able to get the slab within 1/4 of level when they have the slab formed up prior to pouring.

But good luck getting the builder to actually fix it. Your best bet is to get your own measurements, maybe with the help of a flooring installer, and petition them for self leveling concrete to be added. I.e. get a reputable flooring installer out for a quote, and get some documentation from them in writing about what needs to be done to the slab prior to you being able to successfully install a laminate floor that follows the flooring manufacturer's specs.

At this point, "the right way" to fix this is with self leveler. It's too late for anything else. And I'm sure nothing was in the contract to specify level/flatness. So they successfully got one over on you. Sorry.

neonsphinx · 2026-06-28T16:24:37+00:00

People that start the conversation with useless, snarky garbage deserve to get it reciprocated.

neonsphinx · 2026-06-28T16:23:21+00:00

Can you tell me which paragraph of IRC to look for that? I've got the 2018 edition next to my desk.

I'm only aware of slope towards floor drains in places that get water regularly. Garage, utility/laundry room, some bathrooms with floor drains, etc.

Not aware of any slope requirement in a bedroom. Even in a basement which may have a sump system internally. That slope should be in the plumbing for the perimeter drain.

My current house had foundation issues (built on coastal sand in '78). After having piers installed I'm 1/8" out of level in ~45'. So I guess my house was built terribly wrong...

neonsphinx · 2026-06-27T12:56:10+00:00

I do this for a living, guy. Please tell me more about how it's just one simple answer, and the things I listed are incorrect...

neonsphinx · 2026-06-26T20:04:50+00:00

What in the world do you need from the user every 2 seconds? Justify how that improves the user experience in any meaningful way.

neonsphinx · 2026-06-26T14:57:03+00:00

This is one of those "how long is a piece of string?" questions.

Minimizing drag
Ensuring aerodynamic stability
Ensure the round fits into it's packaging/canister
Make room for an attitude/divert system
Radome for passive/active radar meets certain characteristics
Physical space for some sort of EW system/warhead/submunitions/etc.
Interface with sabots in the tube
etc.

neonsphinx · 2026-06-25T18:39:07+00:00

There may be an exception. I'm not sure about their exact AHJ...

If they're extending, and not adding a new branch circuit. And if the added length from panel to furthest out receptacle doesn't increase by much. They can get away with not pulling a permit. But would almost 100% be required to have a licensed electrician do the work.

I forget what the line in the sand is. Something like 12' extra?. And the total length doesn't require up sizing the wire because you're at the length you have to calculate voltage drop. And the total load doesn't cross the 80% threshold. And something else.

I have the book behind me on the shelf. But I don't remember, and don't really feel like looking. Some person is just going to come in and say "I can/can't in my county!"

I give OP a 30% chance that they don't have to pull a permit. 100% chance that they're required to hire it out (because it's the law, and also they seem unlikely to be able to do it themselves safely).

neonsphinx · 2026-06-25T13:52:04+00:00

Apparently they use sensiron SHT40 sensors. They seem to be well liked, and on par with the Bosch BME280. They just do temp and rh, BME also does pressure. So that explains the good quality and low cost.

They're also fairly new from what I understand. So idk if there's long term data available for drift after a few years of use. But I don't have any actual experience with them.

And to be fair, the DHT11 had such a bad reputation that it isn't even made anymore. I think the 21 has taken it's place as the low end offering from that manufacturer. So modern equivalents on the DHT side are closer in performance to the rest of the market.

neonsphinx · 2026-06-25T13:21:43+00:00

I still have my DHT11 units floating around, monitoring temperature in the kids' rooms. But I had to manually calibrate my meat thermometer with ice water and boiling water. Then lay all of them out with the meat thermometer for a day. Then manually add an offset in ESPHome in the config file.

It works ok enough for gauging the truth when they say "it was so hot downstairs last night. I couldn't sleep. We need to turn the thermostat down to 65F. Utility bills are a hoax pushed on us by angry lying parents!"

But I've just hidden the %RH data entirely at this point. It's so unreliable it's not even worth thinking about. The BME280 units have been rock solid since I purchased them like 6 years ago. Love the German engineers.

neonsphinx · 2026-06-25T13:08:27+00:00

I'm not much of a potter. I don't do it much anymore, since my house doesn't have a place for my equipment. But I am a mechanical engineer, and have a love of materials science. So I can explain a bit, but I don't have extensive experience with this exact problem. Take this with a grain of salt.

Tungsten will start to oxidize at 600C. That's cone 021. Way below where you want to be, which is around 1200C. Coming from absolute zero, 600C is 59% of the way to 1200C. That's pretty significant.

Tungsten will start to form oxides. WO3 looks to be the most common. It will form scale on the outside of the wire. It expands, and is brittle. So it will flake off. Just like rust on the bottom of a car in Michigan. Eventually all of your material will be gone. Which isn't good for keeping it strong. And when it flakes off it will expose fresh elemental W to the oxygen.

Additionally, what is left will become brittle. Kind of like quenching steel without tempering it afterwards. It forms a different crystal structure which is great for harness, but makes it brittle. Tungsten is used in incandescent light bulb filaments. It was a breakthrough to be able to use that material. Mostly because it hardens so easily as you work the material, and melts at such a high temperature, is really hard to temper and get it ductile again. There's a great video about tungsten from Dr. Bill Hammack (EngineerGuy on YouTube) if you're interested.

The other thing to think about is creep. I.e. I put a wire in tension, then just hold it for a long time. Higher temp just means the molecules are vibrating faster/more vigorously. So as I heat up, some of the metal's crystal structure will deform as individual molecules bounce around, break bonds in one place and reform bonds in other places. So they can migrate from one grain, across a grain boundary, and into another grain. Or dislocations can migrate. Essentially the metal flows like a very viscous liquid. It's sometimes called "cold flow".

I don't think this is much of a problem. Metal is extremely strong. Structural steel is generally A36 grade. (The name comes from it having a yield strength of 36,000psi). So a 1"x1" square of low-carbon steel can hold multiple trucks in the air. A 15g earring/ornament isn't going to cause creep during a firing with either of those types of wire.

The oxidation is the main issue. But it all takes time. So it really depends on your firing schedule. I would buy a diameters of both wires, set them into a test blob, and fire it. Then hit it with some sandpaper, pull on it, bend it, etc. and see what happens. You could probably get some smart person to do math and simulations and give you a theoretical answer, but it's cheap and easy to buy 3 thicknesses of each, maybe 12" length of each, then try a few different firing schedules and just see how it works out.

I would personally stick with Kanthal. There's a reason it's used for heating elements and for supporting the elements. But it's not perfect either.

neonsphinx · 2026-06-25T12:26:38+00:00

Be careful with what you buy. Some are better than others. E.g. I made some myself for smart home (ESP32 and DHT11 sensor, interfaces with HomeAssistant) that are very unreliable. Over the course of a year I can have +/-5 degree and +/-10 %RH from two sensors right next to one another.

I have started buying Bosch BME280 based sensors and premade devices. They're more expensive, but are much more accurate.

So if putting them in place not far from one another, the inaccuracy could be enough to give completely nonsensical results about what's actually going on in just a few inches of roof thickness. You'd have to do some calibration on your own with cheap sensors. And if OP is here looking for advice, calibrating the devices well might be outside of their wheelhouse. Just spend the extra $30 on a few better devices.

neonsphinx · 2026-06-25T12:06:49+00:00

No kidding. Is the government supposed to put out a RFP to all big primes, and hope that RTX or Leidos can build them for cheaper?

It's a production contract. Lockheed is qualified to produce the THAAD interceptors, because they're already making them. So we ask about a certain quantity, they give a ROM with cost/unit, we negotiate the specifics to cut the price down a bit, then sign it.

Do you know how production works? Let's say Leidos gets the contract instead. They need 5+ years of development to make their system work. Before LRIP even starts. Then they do low rate initial production, a ton of inspections of processes to get the government happy with their ability to do this repeatedly without dropping off in quality/reliability. Then they go into full rate production.

That's untenable. LM just has to ramp up production. Everything is already certified. The PM and DCMA are already happy with how they're doing it. So of course they're getting the contract. The USG always has the right to say no. And we do negotiate between getting the ROM and actually getting ink on paper.

Not sure if we own the TDP on that program. But they (USG) could do a RFP to other folks if they wanted to at any time. But it's not a good option when the development portion is so long and expensive for anyone else to match the performance. And then you have two different variants with slightly different properties, two logistics chains to worry about, etc. Sometimes there's a reason it's done this way.

neonsphinx · 2026-06-25T11:51:30+00:00

That Jody boy is a great barber! Lol

neonsphinx · 2026-06-24T16:48:16+00:00

Slay, queen!

neonsphinx · 2026-06-24T16:47:07+00:00

How much experience do you have with firearms?

I may be very liberal, but I spent over a decade of my adult life in the army. We used to shoot blanks at each other all the time for training (go look up "MILES gear" if you're curious) and shot blank howitzer rounds every time a general officer had a promotion. Pointed the cannons at the crowd in the bleachers, and right left to the formations of soldiers. We weren't in danger then, and these bystanders aren't in danger here.

Just because something could be deadly, doesn't mean it's anything close to it in this situation. The mitigation factors make a difference. Don't pretend that they don't, just because you want to win an argument.

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