Deterioration of Buildings

Deterioration of Buildings

Postby skylark » Sat Apr 26, 2014 3:40 pm

The book describes a process where most buildings would collapse within about a hundred years, mostly due to infiltration of moisture through peeling paint or broken windows and the accumulation of trash and detritus. How much of the deterioration of human structures after an apocalyptic event is attributed to neglect/the absence of humans versus an inevitable deterioration that all buildings go through even when reasonably well-cared for (let's say by a rural homeowner who knew how to repaint a wall but lacked the skills/resources to replace their own roof)? It seems to me that buildings receiving some kind of upkeep can and do last longer than 100 years -- and basic home upkeep is a skillset many modern humans do still have.

As for cities, will the environmental threats to those buildings come to haunt us even if society keeps going strong, and leave us with occupied, rotting skyscrapers to contend with, or are there ways that people are continually preserving and protecting these structures that would lapse if society collapsed?
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Re: Deterioration of Buildings

Postby lewis » Sat Apr 26, 2014 11:35 pm

Good question! The figures I gave in The Knowledge were assuming no-one was up-keeping any of the buildings. After an apocalypse and a severe crash in population, maintenance would cease on the vast majority of edifices and they would deteriorate and degrade with the elements. But of course, if survivors were maintaining and repairing the buildings they chose to live in they would last much longer. And skyscrapers need constant maintenance and repair, too. Most modern skyscrapers are constructed using the 'curtain wall' technique, whereby an internal steel skeleton supports all the weight, and the outer cladding - most often glass - simply hangs off this. So once these glass panes start falling off the weather can penetrate into the interior and begin attacking the load-bearing structure. A good book to read-up more on these topics is Alan Weisman's The World Without Us
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Re: Deterioration of Buildings

Postby Billy » Mon Sep 08, 2014 4:20 am

Another thing to consider is how the building was originally constructed.

Our little farmhouse here is over 100 years old, built in the Arts & Crafts style. Built like a bunker. Thick hardwood joists and beams, usually oak or southern yellow pine (a species of pine almost as hard as oak, now almost extinct). Plaster walls. Everything morticed and tenoned, then cross-pinned. All that won't stop a window from being smashed in by the occasional flying tree branch in a storm, but these old homes were overbuilt. Some were even built using square cut nails, which have 400% more holding power than wire-cut nails.

Newer homes are made from soft white pine and spruce, tacked together using what are referred to as "spikes" - No. 16 nails. In the past, the land was cleared and if the trees were suitable, they were sawed up and left to dry and normalize on the build site for up to a year. The wood was also quarter sawn, not slab-sawn like today. This means that when quarter sawn wood dried out, it remained relatively straight. Slab sawn wood does not. When it dries out, it warps and curls - this is just the wood wanting to return to it's natural shape. Compounding the issue is that a company building a house uses wood that is "soaking wet and green"... meaning it has been partially dried in a kiln, but not normalized (wood will gain or lose water, depending on the relative humidity of it's surroundings, which affects its dimensions). This wood is cut and tacked together before the wood has a chance to normalize, and over the course of a year or two - as the wood changes dimensions - the house creaks like a pirate ship. Wood changing dimension also loosens the nails holding the boards together. Whenever you hear someone say "Oh, that's just the house settling" what they really mean is "Oh, the builders skimped on the materials and used wet sticks to build the house". I've been in some homes where the molding is just paper with a wood grain plastic covering over it... it swells when wet and disintegrates...

Modern houses won't last very long if nobody maintains them. Old houses, if reasonably maintained during their lives, will last longer just because of the superior construction and materials that went into them from the beginning.

One of the potential house-killers around here is the black locust tree. Not a big fan. Certain trees colonize newly cleared areas - the black locust is one. They grow fast, are extremely hard, invasive, rot relatively quickly and a stiff wind often knocks them over. One of my neighbors has an old home on his property - the structure is more or less intact, though damaged. The invasive vegetation has taken its toll more than the elements. Vines, ivy, locust trees, etc, are doing their best to knock that old house down, but it's hanging on. My guess is that it was built sometime in the middle of the 19th century, judging by the type of glass still visible...
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