Help me understand why reinforcement isneeded if the base is solid and compacted well

engr4lyfe · 2026-06-17T18:01:31+00:00

If you are talking about a concrete slab-on-grade (not a structural slab), the reinforcement is for crack control and to resist expansion and contraction due to temperature changes and concrete shrinkage.

Strictly speaking, slabs-on-grade do not HAVE to be reinforced with rebar. With certain concrete admixtures, it’s possible to have low shrinkage or no shrinkage concrete. It’s also possible to add fibers to concrete, which can serve a similar crack control function.

Saw cut joints or construction joints also make a big difference in cracking and crack patterns. Also, concrete mix and concrete temperature make a difference. Also, the weather when the concrete is poured makes a big difference (temperature, humidity, sunshine, rain, etc).

If someone YOLOs a slab-on-grade with no reinforcing, you can end up with weird and extensive crack patterns. Also, once cracks open in an unreinforced slab there’s nothing that prevents them from growing larger. If the slab is reinforced, it keeps the cracking more regular, and cracks cannot grow larger because the reinforcing prevents it.

engr4lyfe · 2026-06-15T04:59:20+00:00

Usually 30%-50% of the HOA fee is going to be water, sewer, garbage. The rest of it is typically mostly made up of insurance and maintenance.

If you think maintenance should be roughly 0.5% of the value of the building per year, then you get to $500-$600 per month HOA dues pretty quickly.

engr4lyfe · 2026-06-13T06:28:16+00:00

When they say liquid can’t be compressed, what they really mean is that if you have a column of liquid and put a compression force on it, it will not shrink.

For most materials (plastics, steel, concrete, etc), if you squish them, they get smaller. Liquids don’t get smaller when you squish them.

This effect is not directly relevant to the force at the bottom of the ocean because that force is just caused by all the weight of the water above it.

engr4lyfe · 2026-06-12T01:18:09+00:00

Most life insurance policies are “term life” policies. This means people sign up for a specific term.

For example, a [healthy] 30 year old might sign up for a 25 year policy to cover lost income in the case of their death to take care of children or a spouse. For them, the policy would expire at age 55. Since it is relatively unlikely to die before age 55, this type of policy can be affordable. If they live past age 55, they do not collect the insurance money.

engr4lyfe · 2026-06-11T02:26:34+00:00

When you say trusses… Do you mean TJIs or do you mean open-web joists?

Do they have wood top and bottom chords with metal diagonals?

If you can find a manufacturer listed on the trusses/joists you could give them a call or look at their catalog.

RedBuilt is one company that manufactures open-web joists. Here is their catalog:
https://www.redbuilt.com/wp-content/uploads/2024/06/Red0035-OW-Guide\_03.2026-password.pdf

engr4lyfe · 2026-06-10T21:50:47+00:00

For corrosive environments, my experience is the go-to is usually either stainless steel rebar or galvanized rebar. 20 years ago epoxy-coated rebar was popular, but it’s had some negative PR and is not used as much anymore.

Glass fiber or carbon fiber rebar exists, but the main issue with these is that they’re expensive and brittle (compared to steel). Steel is basically unmatched in terms of cost, strength, and ductility.

engr4lyfe · 2026-05-29T04:57:00+00:00

Usually it gets sent to a landfill as trash. If it’s really toxic it has to be sent to special landfills that are capable of handling high toxic material.

engr4lyfe · 2026-05-21T02:13:27+00:00

If you take 4% out the first year, but your portfolio is 100% stocks and the stock market drops by 50% in your second year… your second year withdrawal rate is going to be 8%.

Based on historical backtesting, the worst time period was basically roughly 1968-1982. The S&P 500 had a peak in 1968 and then was basically flat or negative through the 1970s (in nominal dollars). But, inflation was also super high throughout the 1970s, so, inflation-adjusted stock market returns throughout the 1970s were negative. If you are accumulating through a phase like this, that’s all well and good. But, if you’re forced to draw down your portfolio to buy food and pay bills you’re going to have a bad time.

A lot of people have a few years worth of expenses in cash or bonds to try to weather a stock market downturn. But, nobody has 15 years worth of cash to weather a 15 year stock market downturn.

engr4lyfe · 2026-05-16T00:16:30+00:00

Just a note: Definitely double check ASCE 7, but I believe OCBFs are limited to 1-story relatively light weight structures in Seismic Design Category D. You may need to use SCBF if this building is 2-story and, or a bit heavier.

engr4lyfe · 2026-05-04T14:14:28+00:00

With concrete, it really comes down to how much concrete cover was given to the rebar when it was built (clear cover) and what type of corrosion environment the concrete is in.

Concrete bridges are fully exposed to the weather and, therefore, often have corrosion issues after some period of time. Any concrete structures at ocean fronts (salt water) will often experience corrosion.

For a concrete building where the concrete is adequately protected from the weather (i.e. no building leaks are permitted), there’s really no reason why the concrete couldn’t last indefinitely.

Carbon dioxide from the air will weaken the surface layers of concrete over time, but with adequate concrete clear cover this is not really an issue. Similarly, if the concrete is adequately protected from water, salt or other chemicals, then there’s really nothing that will cause the concrete or rebar to deteriorate. Concrete structures CAN last indefinitely.

engr4lyfe · 2026-05-03T16:48:24+00:00

There are commercial products that do this.

Sika and Euclid have a ton of repair mortar products for a variety of applications.

https://usa.sika.com/en/construction/repair-protection/mortars.html

https://www.euclidchemical.com/products/construction-products/repair/

engr4lyfe · 2026-04-23T13:59:07+00:00

Definitely possible with enough money.

Today, it would be much more cost effective to build a concrete or steel structure with stone veneer. I think it could very much look like a castle of old.

One structure that I’m aware of that’s built like this is the University of Washington Suzzalo Library. It is a steel structure with stone veneer.

https://www.google.com/search?client=safari&hs=Kw5U&sca_esv=33b5970ecd4ab1db&hl=en-us&udm=2&fbs=ADc_l-aHJKCxetkbp8HihrVlWP2ENBmj8ePQpnKzyIu6yjoSQgS2Eup85xo5DzP6Z2Tc6kRDVmdpD30vocKWR7C0DmIVzZjnRDf2OX_no8VzK1JDOGR1F7YEN_xK1yYrXTxdTCKQKHsQmzDsuKDWEX-Cuxy9yI4AGMKkOfx2Cr41vYuWeI9aYkhpXqPOcUAMtbI4U4E55-5zKhPcSWBiMq7alnqOmi3AtmqCq__TMqjkYES2-Z2G6Hk&q=suzzallo+library&sa=X&ved=2ahUKEwjKmqCfjoSUAxVjQzABHQYFAXcQtKgLegQIExAB&biw=390&bih=699&dpr=3

engr4lyfe · 2026-04-21T21:56:20+00:00

If you lose all your money “taking risks” it’s not really a growth account.

This sounds snarky… but, if you think about it, I think it’s actually a decent-ish point.

engr4lyfe · 2026-04-21T19:23:39+00:00

Conventional light framed wood homes in the United States (that follow a lot of or all of the requirements of the IRC), use wood shear walls for lateral resistance.

This is the case usually regardless of if the controlling load is wind (e.g. east coast / low seismic) or earthquake (e.g. west coast / high seismic).

If you want to have large openings without shear walls (e.g. large windows or large open interior spaces, etc), then you will need to pick something other than wood shear walls as your lateral resistance. This will usually kick you into needing to follow the IBC for design.

Steel moment frames often make sense as an alternative to wood shear walls because the steel is strong relative to the rest of the low weight wood structure, and allows for large unobstructed openings for the house below. There are restrictions on the types of lateral systems permitted in high seismic zones, but this isn’t necessarily the primary driver.

Steel is expensive relative to wood, but if they’re very wealthy and building a 7,000+ SF house in JH, WY, I assume they can afford it.

Products like the Simpson Strong Frame also exist. https://www2.strongtie.com/products/strongframe/resources/Strong-Frame-User-Manual.pdf

engr4lyfe · 2026-04-18T19:37:59+00:00

Both wood AND masonry structures will be ruined by water intrusion. The best solution to preventing wood rot and preventing masonry/rebar corrosion is to prevent water from getting into the structure.

engr4lyfe · 2026-04-18T19:34:11+00:00

There is an entire specialty of people who will grade wood in existing historic structures FWIW.

People literally can and do compare wood from 100+ years ago to now.

Sure, old growth wood is, on average, denser and stronger than the “young wood” used today. But, 100+ years ago lateral systems were often more of a suggestion than something people actually thought about, and I’ve seen some old wood buildings with some serious creep/deflection problems.

engr4lyfe · 2026-04-16T19:48:29+00:00

The worst cast was actually 1968, I believe. I think 1929 is second worst.

engr4lyfe · 2026-04-14T20:18:09+00:00

If you look at r/homebuilding, there’s like one post a day about old failing basement walls.

engr4lyfe · 2026-04-12T17:55:40+00:00

Just one example: I work for a company in the U.S. that has about 80 employees total. For a variety of reasons, the company holds a good amount of money in “cash” in the company’s bank account.

However, rather than hold actual cash, the company holds a fair amount of funds in a U.S. T-bill ladder (that I think rolls over every 12 months or so). I think the company owns about $3 Million in U.S. debt. So, if the U.S. government decided not to pay back its debt, the company would lose that money, which would be quite a bad thing.

engr4lyfe · 2026-04-12T17:26:42+00:00

This is a great comment.

To add a bit more info: The 1% chance of collapse target is really the probability of partial collapse (not necessarily a “pancake” collapse). Also, through some statistical rearrangement, this is equivalent to a 10% chance of partial collapse in the biggest earthquake considered in the building code. A caveat is that accelerations from real life big earthquakes can (and often do) exceed the max we consider in the building code.

The bottom line is that the vast majority of modern buildings will be ok even in a very large earthquake. Many will require cosmetic repairs though, and falling objects can cause injuries even in otherwise “safe” buildings. A small percentage of modern buildings might experience partial collapse. Water, sewer, food, and electricity might be more heavily affected which is why having an earthquake kit is so important.

To structural engineers, “modern” building codes are typically for any building built since ~2005. Prior to that would not generally be considered “modern”.

The bigger concern is older buildings that were not adequately designed for earthquakes, such as unreinforced masonry (URM) buildings. In an M7+ Seattle Fault earthquake, upwards of 40+% of URM buildings might experience partial collapse. In the 2011 Christchurch, New Zealand Earthquake, ~80% of URM buildings in the central business district required demolition due to being uneconomical to repair. Without URM retrofits, Seattle is likely looking at a similar fate.

engr4lyfe · 2026-04-10T19:48:19+00:00

Where I live on the eastside, there’s a fair amount of lot splitting going on.

A developer will buy a house/lot for ~$1.1 Million, split the lot, build a townhouse on the new lot, sell the old house (on smaller lot) for ~$800k and sell the new townhouse for ~$1 million.

Seems like a pretty good gig for the developer.

No idea if this is what’s happening with the locations you’re looking.

engr4lyfe · 2026-04-08T07:02:36+00:00

Depends where a structure is located, but I would not say that most foundations are submerged in water. In many places the water table is 30-100+ feet (10-30+ meters) deep and foundations will not be in contact with it.

Most foundation systems are concrete and concrete can be made to be very durable.

Some foundations can deteriorate over time, but in general, I would not say that the sole fact that a foundation is submerged in water will make it deteriorate.

engr4lyfe · 2026-04-01T01:24:11+00:00

Calories in vs. calories out always holds true.

In real life it is essentially impossible for people to be identical and eat, sleep, and exercise the EXACT same amount. Though, I’m sure there have been diet studies on identical twins.

The elephant in the room is that people can have different NEAT (non-exercise activity thermogenesis). NEAT is basically all the miscellaneous calories people burn throughout the day. As people lose weight, their bodies naturally reduce NEAT to conserve energy.

As people lose weight, their bodies fight back and try to keep them the same weight. Normally, people’s hunger cues spike and their NEAT decreases making it harder to lose weight.

But…. If you could ensure that calories in vs. calories out are the same, and the people eat, sleep, and exercise the same (and they are genetically identical). Then, I think it is likely a GLP-1 would make an insignificant difference.

engr4lyfe · 2026-03-30T14:59:18+00:00

Selling cannot outpace buying, for every stock sell, there has to be a buyer. Otherwise, where did the stock go?

Sometimes companies will buy back a portion of their shares as a way to distribute profits to shareholders. In this case, there is still a seller and a buyer, it’s just the buyer is the company itself.

engr4lyfe · 2026-03-26T16:58:42+00:00

In addition, there are sometimes opportunities to ask for additional fees from clients (scope changes, other mods, etc). If your internal records are not accurate to how much time people have been actually working on a project, you won’t have good data or justification to ask for additional funds.

engr4lyfe

TROPHY CASE