Comment by vlehto | Hacker News Reader

Comment by vlehto | Hacker News Reader

It's often surprising how much of building codes are about fire safety. Occasional hazards practically define your day to day environment.

The most fire sensitive part of a high building is the staircase. You want long burn time in fire but also have very little "fire load". (Amount of energy released from material that can burn in typical fire. Typically MJ/sqm.)

Steel staircase gets you 0 fire load but relatively short "burn time". Because steel gets soft at relatively low temperature and more importantly conducts heat very well.

Pure concrete stair case is better, but you get cracking that shortens the burn time.

Wood is surprizingly good for burn time, but you greatly increase the likelihood that the fire will start form the staircase. Which is really big no-no. Sometimes even burning a complete house (starting from somewhere else) is lot better than just burning the emergency exit.

The only really good option is reinforced concrete. The concrete insulates the steel, which provides ductility to the whole structure. With reinforced concrete staircase and stairwell, it's questionable how much you benefit from wooden load bearing structure.

I think it can be done. And it can be done really well too. But you may need to step away from typical architecture and step into something more modular.

There's a reason for that. My father in law was a fireman who retired as chief after 45 years.

Fires are rare today -- but were incredibly common during the 60s and 70s. He was at an average of two a week in those days. It was common enough that insurance companies had "protectives" who were firemen to go in and pull out your furniture.

Fire is rare because of those codes today.

Even 60's were safe compared to earlier centuries. It used to be common for whole cities to burn down. And again we can thank the codes.

The development of pressurized water systems and thus the ability to quickly extinguish fires likely had a pretty significant impact.

The first Steam-pump fire engines only came into (very limited) use in the 1850s and ICE pumpers in the early 1900s.

Fire codes at the time required wide paved streets to act as fire barriers. You get double benefit when you can get your fire engine to the desired location by that new fat street.

And then again reinforced concrete also became available around 1900.

So yes, the code is only small part of all that. But I'd claim it's significant part.

Electrical lighting made a huge difference in fire safety.

Plus, insurance fraud was at an all time high, detecting accelerants was very difficult, people smoked in bed, people smoked everywhere. As a kid, all I remember is adults lighting cigarettes. My job was stomping out the butts.

Source:watching Goodfellas, and that movie with Bull--forget the name--Backdraft.

You need a source on HN when quoting childhood memories?

Does the reduction in smoking in our culture (especially smoking in public) have any bearing on fewer fires?

A slight decline for smoking materials but a big decline for 'matches' over the past 5 years in the UK, according to data. https://www.gov.uk/government/uploads/system/uploads/attachm...

Source: https://www.gov.uk/government/statistical-data-sets/fire-sta...

The introduction of smoke detectors (the typical 9V battery driven type didn't show up until the 70s) likely helped quite a bit.

From following the local fire brigade it seems that the most common source of alarms is people forgetting a frying pan or similar.

The building codes are about life safety of which fire safety is a component alongside more common hazards such as trip and fall; electrocution; cholera, bubonic plague and influenza; and plain old collapse.

From a practical standpoint, the biggest issue with wood construction is not fire but dimensional change due to moisture [both bulk water and humidity] in addition to dimensional changes due to temperature. The differentials with other materials make systems [such as HVAC, electrical, life safety] more complex mechanically.

In terms of steel, intumescent spray fire protection, masonry, and gypsum board are common alternatives to concrete for fire protection of steel. As a tangent to the issue of differential expansion, the reason reinforced concrete is practical is because steel and concrete have very similar coefficients of expansion as moisture and temperature vary.

I'm not convinced. Only systems that require rigid piping are sewers, air conditioning and sprinklers. (But does air conditioning really require rigid piping?) Sprinkler system is usually quite rigid, but is there any reason why you could not use flexible parts every now and then? Hydraulic machinery routinely has 60MPa in flexible hose.

Laminated wood should have smaller heat expansion coefficient than steel or concrete. Obviously this can turn into problems if you hot air conditioning steel pipe gets longer than the surrounding building.

PVC has significantly higher thermal expansion coefficient than any of these. So the collars have to have some give anyhow.

If you get moisture swelling, you are fucked anyhow. Wooden building has to be designed so that you stay between 17% - 20% moisture content at all times.

Currently wooden small houses have their lateral support done by steel. I'm really skeptical how much this really matters.

You may want to sit down and look at the thickness of your typical hydraulic hose. They seriously do not take curves well.

Let's say you have 15m long corridor in wooden house and you need sprinkler system along the corridor. If you have temperature increases 30C that may cause your sprinkler system to now be 5mm longer than it was before in relation to the size of the house.

Now we could have suspended the sprinkler pipe to the roof so that every suspension point allows 1mm sliding movement. Or we could have replaces 1 meter section of the pipe with hydraulic hose and leave it slightly bent.

Doesn't sound like an issue really.

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