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What physics knowledge would be required to build a house?

  1. Oct 18, 2016 #1
    Curiosity question: What physics knowledge would be required to build a house?

    I am not going to build a house, this is just a question out of curiosity because it may not look like, but I think that a well built structure may actually be something complex that employs many physics concepts.

    I'm guessing Statics and Dynamics. What else? Would Materials Science for engineers be relevant?
  2. jcsd
  3. Oct 18, 2016 #2


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    It's not all that complex. After all, people have been building houses and other structures for thousands of years. I believe that the way things normally work is that an architect makes a basic design for a house, and then a structural engineer looks at the design and specifies the materials needed for construction, adhering to local and national building codes. A structural engineer would have training in both areas you listed. Things you didn't mention are the electrical wiring for the house as well as the plumbing. I imagine these fall into the areas of expertise of a structural engineer, but someone would need to plan the number of electrical circuits and include plans for running pipe to bathrooms and the kitchen.

    Some of the things to consider are 1) the height of the house, 2) the pitch and strength of the roof, and 3) resistance to earthquakes. If the house is more than one story, the lower story has to be able to support the weight of the house above it. If the house is built in an area of the country where it snows, the roof has to be able to support a specified thickness of snow without collapsing. For earthquake resistance, the frame of the house has to be firmly fastened to the foundation so that it doesn't just slide off.

    I'm sure there are a lot of things I've omitted, but these are the things that came to mind.
  4. Oct 18, 2016 #3
    I guess it depends on the house right? I had a buddy build a vanilla 1000sqft ranch house with his dad in high school and at the time he was a C student (although always very interested in "hands on" stuff). I think his dad was an average electrician. Looked good in the end.
  5. Oct 18, 2016 #4


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    Building a house requires exactly zero book knowledge of physics. Did you really mean designing a house?
  6. Oct 18, 2016 #5


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    A few years ago I bought a 10' x 14' shed from Lowes.I could have put it together myself, but I decided to have them do it for an extra $200 or so, as they could do it in a day and it would have taken me several weekends. Also, I knew that I wanted to wire the shed, and that would take me some time to design and install.

    My little shed has two 20 amp circuits. One circuit is for a heater and three fluorescent fixtures hanging from the rafters and a couple of smaller fixtures under a shelf over a workbench. The other circuit is for several receptacles near floor level. I wanted two circuits so that I wouldn't trip a circuit breaker by turning on some tool while the heater was going. All the wiring runs through a conduit that the previous owners had used to power a circuit for an RV.
  7. Oct 18, 2016 #6


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    Wind resistance is another factor in some parts of the country, e.g., east coast and Gulf coast. Proper bracing (and strong joints) is needed in the roof structure.

    In parts of the country where the ground freezes for prolonged periods, local/state codes often include a minimum depth below frost line for footings.

    Some knowledge of mathematics is necessary, especially when making changes to the design, or cutting different lengths of wood or trim to make it fit.

    Common sense helps.
  8. Oct 18, 2016 #7
    I suppose, yes. I was thinking that if for example one makes four walls and a ceiling, the ceiling will exert some force over the walls and so I thought that knowledge of how to calculate those forces was required in order to prevent the walls from breaking or the ceiling from collapsing. The math and problems one solves in a statics course provide a little of that knowledge, but I thought that it couldn't be that alone. That there must have been other physics concepts to know in order to make a house.
    Look what I found, this is very cool. Well, I cannot show you because the book is copyrighted, but in my own words, I just remembered and went to re-read in my book of materials science that there was a time in which the copper pricing increased and therefore some people started using aluminum wiring in a number of buildings which ended up causing fires. Then it explains the reasons of why aluminum wiring caused fires. One was because of thermal cycling and it explains that in detail. It also points out that the coefficients of thermal expansion of aluminum are different than copper which caused loose connections. Mechanical stresses were also to blame. It explains also that aluminum oxidizes faster than copper and that such oxide increases resistance and therefore the heat as well. All in all, according to what I was able to conclude from the book, there are way too many reasons to not choose aluminum for wiring. Although the book later explains a way to circumvent such problems.

    I am guessing that such is an important piece of understanding if someone were to make a house... if they don't want it to catch fire. What I like about the book is that it goes and explains it in a scientific way. It isn't just because someone tells you not use aluminum as wiring and that's it, it is because there is actually a scientific reason behind it and an explanation. I just wanted to share that little piece of information.

    So I suppose Materials science knowledge would be required then.
    I was thinking about it, but wasn't so sure how it affected a building. But then again, you are right indeed. There are physics involved regarding the force the air exerts over the building itself, so I guess that should be taken into account on the calculations.

    Going a little of topic: I would love to live in a windy place :smile:.
    I see. That's a very good list. I indeed missed those. But that knowledge is definitely required.
  9. Oct 18, 2016 #8
    It doesn't require any physics or even math knowledge to build even a relatively sophisticated edifice, provided you are willing to learn by trial and error. There are examples from all over the world of indigenous people building very solid and comfortable permanent dwellings with no concept of physics. You repeat what works and avoid what fails, and over time you arrive at a good house design.
  10. Oct 18, 2016 #9


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    I stick built a simple work shed a few years ago. Very little physics or math was needed to actually build it but a little was needed to design the trusses for the metal roof sheets. The most important design tool was beer and a boombox.

    P5090043.JPG 100_0280.jpg 100_0285.jpg 100_0289.jpg 100_0306.JPG
  11. Oct 19, 2016 #10
    I don't know. I'm not so sure that is a good approach. I think everything should be adequately calculated and I am guessing trained people that build houses do that.

    I know one can make what one can make disregarding physics and not caring; like putting one stick here and another there, but I don't think it will be a good structure and it could call for disaster. It's better if the person understands the underlying physics.

    Mini story:

    Some years ago, there was a storm approaching and the government sent some pamphlets for the citizens explaining how to protect their houses. Some citizens didn't buy the materials and didn't do anything not because they didn't have the money (they had they money), they refused because they thought the government was lying and it was just a scheme to extract money from them. Their houses got effectively blown out. Then they were asking for help. I didn't laugh at their disgrace because I wouldn't like someone to laugh if I ever fall into such misery. Instead I was a kid, yet I helped them take the debris and water out of whatever was left of their homes. My parent's house was intact because they did buy the materials and installed them according to the instructions the government handed out.

    Bottom line of the mini story: I am guessing that the government hired people to write those pamphlets and that such people had knowledge about physics of how to protect houses from strong winds.
  12. Oct 19, 2016 #11


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    Well, the reality is that the people who design buildings and the people who build them are not the same people. And I think that is a good thing because it compartmentalizes the skills, enabling both groups to be better at their jobs.
  13. Oct 19, 2016 #12
    Almost anything with a roof can be called a "house". That's good enough to other animals who build inhabitable structures. It'd be a heck of a lot more difficult to survive if specialized knowledge was required to create a shelter of some kind.

    Modern human structures are designed with new and more advanced knowledge of basic physics, but that knowledge is not necessary to build a house. That's just sentient privilege.
  14. Oct 19, 2016 #13


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    I live in the Columbia River Gorge wind zone so that was a concern for my shed project that I easily solved with hurricane ties and PL Premium (don't use it for anything that you might EVER have to take apart:-p) from the local hardware store.

    Typical winter winds.

    A simple knowledge of good construction techniques is all that's needed today because an engineer designed retail parts to handle the required wind loads.

    You can see the ties in this roof detail photo.
    Last edited: Oct 19, 2016
  15. Oct 19, 2016 #14


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    They built the pyramids without having any knowledge of the underlying physics. Or did they? :wideeyed:
  16. Oct 19, 2016 #15
    It's actually a really good approach. The kinds of traditional structures I'm talking about tend to be over-built, from years, decades, and centuries of retaining what worked and discarding what didn't. The goal is always to arrive at the longest lasting structure given the materials and environment. The design American settlers (none of them physicists) passed around to each other for a home was the over-built log cabin, for example, not some rickety wood frame thing designed to cut down on the number of trees required per house.

    The advent of engineering by use of physics and math, counter-intuitively, allowed things to go the other way, in that it enables very precise estimates of how weak a thing can be made to be while still falling within some artificially set parameters that usually involve money and local politics in addition to function. In other words, for example, by modern engineering standards, the pyramids would be considered a failure: they cost too much, and took too much time and man-hours, considering their completely non-practical functions as tomb/monuments for Kings. Today, a tomb for a King would probably be allotted some arbitrary life span, such as 200-500 years, and designed and built accordingly. There would be no over-building such that it would still exist 3000 years later. Unfortunately, physics is often pressed into the service of planned obsolescence, rather than product integrity and longevity. Architects design houses to have some limited life span beyond which they start falling apart. Of course, they are also designed to have some minimum required structural integrity, which physics provides, but you don't actually need physics to achieve that.
  17. Oct 20, 2016 #16
    The knowledge part already being engineered, deployed and readily available in hardware form is very true.
    Now it won't be taken down by the wind. But did you calculate whether it can be taken down by a truck and took protective measurements against it?

    I'm just kidding :biggrin:. Hihi. You'll probably tell me: "It's supposed to be a shed, not a nuclear shelter, ocean proof, ballistic proof, and meteorite proof structure. Just a humble shed." :oldlaugh:
    Sorry, I had to look for the meaning of that word to understand :oops:. I agree with that. That's a very good observation of yours.
  18. Oct 20, 2016 #17


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    The deck would take a pretty good knock to bring it down. It's build on a slight slope so I dug some nice deep holes to anchor it with concrete so I think it could handle a 'small' truck. o0)
    P5090044.JPG P5100049.JPG

    It's over engineered for a simple shed but that's part of the fun of building stuff.
  19. Oct 21, 2016 #18
    I was kidding, but you did prepare it very nice. Hehe.
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