Since plastic doesn’t biodegrade, why aren’t more houses built with plastic instead of wood parts?


Since plastic doesn’t biodegrade, why aren’t more houses built with plastic instead of wood parts?

In: Engineering

Long pieces of plastic which are strong enough to support a house are pretty expensive and heavy; it’s easier and cheaper to build a wood frame and then wrap the whole structure in thin layers of waterproof plastic + other waterproof materials to keep everything dry.

Because heating/cooling your home would be problematic.

I don’t want to end up like a leftover in the back of the fridge.

It might not biodegrade but it does degrade. Especially many plastics are extremely susceptible to UV, going weak and brittle in comparatively little time.

Structural plastic is softer (weaker) and more expensive (or at least it was until the recent lumber shortage), and it’s also susceptible to damage from UV rays in sunlight (plastic exposed to sunlight will become brittle and crack and break). Plastic with additives to deal with the UV are even more expensive.

We do use a lot of plastic in home construction, just not structurally. Plastic sheeting for moisture barrier, plastic water pipes, plastic (or more accurately polymer) electrical junction boxes, plastic (polymer) wire insulation, kitchen cabinet veneers are sometimes made of plastics, etc.

Plastic and wood will lose strength and splinter apart over time in almost exactly the same way.

But wood will break down/rot into a dirt like substance which is full of nutrients that can feed new life.

Plastic just breaks down into smaller and smaller particles that replace food for animals/insect’s, but is empty of all nutrients and unable to be processed by animals that eat it.

Over time it will build up in the animal’s digestive system.
Eventually contributing to or causing death.

Plastic is not biodegradable but it is not particularly strong not it isolates heat very well. Also, since it is not biodegradable, it would make ecological catastrophe.

It should be noted that wood used in the construction of houses is treated to make it harder to biodegrade. It may also be protected with a varnish or polycoat if it will be exposed to the elements. The vast majority of wood in a home will *not* be exposed to elements beyond some humidity. There’s also not a whole lot of organisms that are good at destroying and decomposing wood that don’t require a ton of moisture (like fungi) and usually aren’t immediately dangerous as long as you take care of your home even a little bit. Homeowners go through a lot of trouble to prevent the ones that *are* immediately dangerous (like termites) from getting into the home.

Houses can survive even pretty substantial natural disasters like flooding and still remain structurally sound. There are centuries-old houses with the original wood structure that are still standing today. The biodegradability of wood just isn’t a concern when it comes to making houses out of the stuff, provided you take care of it properly.

On the other hand, wood is cheap (current shortage notwithstanding), pretty lightweight, flexible, easy to cut, often aesthetically appealing, sustainable (when properly managed), and ubiquitous in many countries. There’s no reason *not* to use wood framing when it’s available and affordable.

Wood is cheaper. That is all.

You could make plastic equivalents to the structural timber used for houses but lengths of 4-by-2 are amazingly cheap. Plastic replacements would have issues to overcome but you can be that, if there was money in it, the industry would find a way. Two that occur to me are that: nailing plastic wouldn’t work well and you’d need to change the fixing systems used; and sunlight kills plastic so you’d have to take care to make sure it didn’t penetrate to strutural members.

Of course using plastic to replace wood would be an environmental disaster but that factor still loses out economics. There’s a huge amount of plastic already used in home construction. My house is clad with foamed polystyrene 4″ thick.

Plastic degrades when exposed to UV light, which a building would be. Plastic also doesn’t like to hold up to consistent loading; even a slight weight, applied for a long time, will cause plastic to sag. That said, a lot of a building is plastic: the vinyl siding and flooring, the moisture barriers, the glues inside engineered lumber, the insulation; just not the structural elements.

If it’s kept dry, wood will last centuries. And actually gets stronger with age.
Plastic would be worse for the environment, a lot more expensive, harder to work with and doesn’t perform very well structurally. There’s really no reason it would ever be used for that purpose.