How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues • Hacker News Board

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#211

Post by jimnotgym » Fri, Jul 17, 2026, 7:48 PM UTC

ErroneousBosh wrote: post #105

PunchyHamster wrote: post #77

Earlier quoted context omitted.

> I think people are often surprised how little materials cost affects the total cost of a job. It's because they frankly never did it. Nobody that had to contract something around the house is surprised by cost like that, it often costs more than price of renting equipment + you doing it yourself 3 times slower than an expert would did it, even if you're paid well. There is reason there is so many DIY channels, labo…

Yeah. I mean I just had some concrete slabs laid to put a bike shed on (literally bikeshedding, the colour is green, that's what it comes powdercoated in from the supplier, take it or leave it). It was 300 quid. I could not buy the materials for 300 quid. Two guys showed up with eight slabs, half a tonne of Type 2 and half a tonne of sand, and then the next day the landscaper showed up and did about six hours of work…

My experience when i was in the trade is very few people know what perfect looks like, and so are perfectly willing to forego decent workmanship in favour of cheap. One of the reasons I left the trade, you could make more money doing a bad job, and I had no desire to do that.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#212

Post by Groxx » Fri, Jul 17, 2026, 7:51 PM UTC

iknownothow wrote: post #111

meindnoch wrote: post #97

Earlier quoted context omitted.

>Cement/Concrete (based on Portland cement) is water proof That's patently untrue. Otherwise we wouldn't need concrete sealants.

You are correct. I'm not sure why I remember cement to be water proof. Its possible I infered from how its been used around me. I have seen cement very often used where water contact is expected (bathrooms etc). I have also seen brick walls plastered with an extra layer of cement as putty considered to be rain proof and any leaks were thought of as poor workmanship rather than poor material choice. P.S. I'm not a bui…

Might be because it's water tolerant, i.e. it doesn't break down with exposure to water? Roman über-concrete stories are always full of "check out the concrete that's sitting in sea-water, it's still going strong! maybe it even helps!" cases too.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#213

Post by jimnotgym » Fri, Jul 17, 2026, 7:56 PM UTC

Brendinooo wrote: post #174

rkangel wrote: post #82

Earlier quoted context omitted.

There are some downsides, but most people on the UK would prefer houses that were 100+ years old. In the village I live in the houses immediately around me are "only" 50 years old. Most of the ones on the main street are well over 100 years old. Housing tastes don't really change that much. Yes over the years we've had to fit things like double glazing and better insulation but that's a whole lot cheaper (and better…

Having been around enough houses (in the US) to have a balanced opinion - I personally prefer older houses but - older houses tend to be a lot more inefficient in their use of square footage - the rooms inside tend to be a lot less open, and one man's "fun/quirky layout" is another man's "why do I have to go down a step then immediately go up a step to cross a hallway" - and, I begrudgingly admit (as I don't like how…

Cupboards, nooks and crannies are one of the things people like in an old house. They are often a side-effect of chimney and fireplace construction. A new house in the UK has nowhere to put anything!

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#214

Post by DANmode » Fri, Jul 17, 2026, 7:58 PM UTC

gravypod wrote: post #116

tpm wrote: post #113

Earlier quoted context omitted.

it's not waterproof

Neither is grout. Grout is water permiable. You shower is water proof from the water proof backing we install the tile on top of. Cement board + roll on or something like kerdi system. https://youtu.be/B5DVpruLygw?si=jD8eMHHGQoWG4hI2

My shower is waterproof because it’s a one-piece insert made of plastic.

Other shower materials that aren’t absolutely insanely stupid include glass, quartz, and other non-porous materials.

Because biology.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#215

Post by jimnotgym » Fri, Jul 17, 2026, 7:58 PM UTC

happyopossum wrote: post #198

freedomben wrote: post #167

Earlier quoted context omitted.

ah interesting! That's quite different from the areas I've lived in the US. If you're in or near city lines the lots on older houses are small. It's not uncommon to see .15 acre lots. Newer houses aren't much better, but you can see .2 to .25 acres relatively commonly, though those are nearly always on the outer city or outside city lines so it could just be proximity to the city that's the factor there rather than a…

That is highly location dependent. Many cities had/have large lots in older neighborhoods and have transitioned to zero-lot-line construction or smaller lots in the past 30-40 years as demand for housing grew. In fact in most of the western US that’s the norm…

The UKs green belt laws haven't helped here. Since you can't make the settlement bigger, the only course is to build in the gardens of houses with big gardens. In my view it has ruined many nice villages

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#216

Post by cogman10 » Fri, Jul 17, 2026, 8:03 PM UTC

iknownothow wrote: post #74

For those not familiar, the secret ingredients are to do with the Lime Cycle [1]: 1) Quicklime/Slakedlime (Calcium Oxide, CaO) 2) Lime (Calcium Hydroxide, CaOH2) 3) Limestone (Calcium Carbonate, CaCO3) To keep it simple, typically you start with Quicklime (CaO) and after construction you end up with some mix of all three and after hundreds of years, the masonry transitions to mostly Limestone with microscopic traces…

> The only thing is, it requires maintainance, which is why Portland cement has taken over the world.

What kind of maintenance and why did roman cement survive without it? Or are we simply looking at ancient survivorship bias where the surviving roman concrete structures survived through the lime cycle without maintenance until it was no longer required?

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#217

Post by jimnotgym » Fri, Jul 17, 2026, 8:04 PM UTC

rkangel wrote: post #157

PunchyHamster wrote: post #79

Earlier quoted context omitted.

Or simpler: people don't exactly want a house layout that was popular 100 years ago. And definitely not the level of insulation it provided. Nor the fact putting any new wiring and piping thru concrete is PITA Tastes change and so do other requirements. but , if we actually built for longevity in use, we could build a very durable shell of a house and then use more perishable but easier to modify methods for inside.…

In my area of the UK at least, the house layouts of houses built last year aren't appreciably different from those built 200 years ago. That's specifically comparing detached and semi-detached houses. Terraces are a bit different now. > then use wood and plasterboard for room walls and floor One of the things I LIKE about older houses is that the interior walls are more solid than plasterboard. There is zero plasterb…

Well, better than most timber frames. If you were to ask for a truly soundproof wall you are likely to get a timber frame in two layers with rockwool fill and double thickness plasterboard.

It was also common to build lathe and plaster covered interior partitions in the past. Way before plasterboard.

A modern one off house may well have concrete block downstairs walls to hold the floor up. Albeit, they may get covered with plasterboard 'dabbed on' anyway, to reduce drying time

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#218

Post by iknownothow » Fri, Jul 17, 2026, 8:11 PM UTC

tpm wrote: post #189

iknownothow wrote: post #154

Earlier quoted context omitted.

It is not lime as in the fruit, it is lime as in the material (CaOH2). Lime the material is the binding agent in lime plasters. It is not likely to get washed away.

caoh2 is water soluble (slightly). the question was about anti-mold properties and it is commonly used for these properties in paint for example in cellars but it will lose these properties when too wet. so it's not used in bathrooms.

Sure but lime plaster can be used in bathrooms on the non shower walls as there's no running water but lots of moisture/humidity which leads to mold growth. As far as using it in the grout behind tiles, you may have a point.

I'm considering applying lime wash between the tiles regularly but not sure what the results will be.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#219

Post by cma » Fri, Jul 17, 2026, 8:28 PM UTC

mikepurvis wrote: post #164

cma wrote: post #30

Earlier quoted context omitted.

There's also stainless steel rebar

Even without the rebar rusting, I think you can still have issues with the steel and concrete having difference thermal expansion properties, particularly for outdoor strucutures where a freeze/thaw cycle is in play. Basically the rebar works itself loose over time and creates micro-fractures in the concrete that then get moisture in them and can cause expansion damage— all without the rebar itself ever rusting or "f…

Maybe so, OP mentioned they were very similar and that still seems to hold for stainless. How about the aggregates within? The composite makeup can result in different CoTE than the individual aggregates, I think that's one part of concrete sidewalks cracking though, sometimes near shaded/unshaded boundaries. Roman concrete supposedly had some self healing properties before the cracks grew, from the lime inclusions.

Re: How Has Roman Concrete Lasted for Millennia? 1,900-Year-Old Latrine Offers Clues

#220

Post by Animats » Fri, Jul 17, 2026, 8:53 PM UTC

giardini wrote: post #204

SoftTalker wrote: post #179

Earlier quoted context omitted.

It's why plumbers use $25 sharkbite fittings now instead of soldering in a $2 copper fitting. But of course the sharkbite relies on a rubber O-ring and will probably leak in 10 years, the plumber will be long gone or the property probably under new ownership who don't remember.

Softalker is right-on in his warning: We usually have a few freezes in the winter and some homes' pipes freeze. I was surprised, in speaking to a plumber, to find that pipe clamp installation had come to dominate the repair market (as opposed to repairing/replacing the leaky pipe). In his first year this plumber had arrived at the plumbing supply house to find all pipe clamp orders backlogged two weeks! He thus deter…

Automated radial welding for pipes seems to be slowly reaching small, plumbing-sized pipes.[1] This has been around for years for larger pipes, but the equipment is now down to home plumbing diameters. Still too expensive, though, at around US$10,000.

[1] https://www.youtube.com/shorts/Jr1TZW8dKCw