Allow for expansion?

[Deguza]

Hello all, Hello all,

Do you allow for the expansion of wood and steel in your projects?

Here is why I am asking:

In preparation to convert a closet to a small bathroom, I and my carpenter buddy are building a new closet.

Here are some photos:

I told my buddy that we should allow some room for expansion for the steel studs up at the top. Since I do not know the coefficient of expansion for this particular type of steel, I could not calculate what the length would be at 60 degrees versus at 95 during a hot day here in San Jose CA.

I also don't have much experience with wood. A Google search turned up that wood expands more with humidity.

There is, of course, the height of the ceiling that may be changing due to heat, humidity, shifting of the ground, etc.

I would have:

- left a 1/4" gap at the top,

- attached the vertical studs to the rails up using a slot rather than a hole, and

- covered the gaps with molding matching the one on the wall...

[trader_4]

No, AFAIK when doing typical framing, there is no factoring in expansion. It all pretty much expands and contracts together with temperature. Steel or wood may be at different rates, but not enough where I've heard of doing anything about it.

[Deguza]

Thank you! I feel better now.

However, I think he should have still cut the wood a bit shorter to save time. He spent so much time trying to get them to fit. He could have saved at least three hours.

[Ed Pawlowski]

Perhaps he is a perfectionist that knows exactly what he is doing. Rather than second guess, ask him. One of you will learn how the best way to do it is.

[Jim Joyce]

Steel studs, at lengths that you'd encounter in a standard residential structure and given the limited temperature swings typically encountered, will not expand or contract at levels that would be cause for concern, so I would ignore that as a non-issue.

Wood expands and contracts with humidity changes, but not along its length to a degree that warrants your concern. 99% of wood movement is across its width. That's why, when you build anything with a wide wood panel such as a dining table, you never firmly attach the top to the frame. You always use clips or some other method that allows the table top to grow and shrink across its width. Its length is not a concern.

Back to your bathroom project: I don't think expansion and contraction are issues that need to be addressed.

[Dean Hoffman]

My first thought is you will be uncomfortable long before any of that matters. How much of a temperature swing do you allow in your house?

[Clare Snyder]

Common mild steel expands 0.0000072 " per inch per degree F temp change. If your stud is 8 feet long (96 inches) at 32 degrees F it would be 96X .0000072 X 68 = .04700 inches longer at 100 degrees F.

[Jim Joyce]

Well, when you put it that way... :-)

[Tekkie©]

On Tue, 10 Nov 2020 17:34:01 -0800 (PST), Deguza posted for all of us to digest...

No carpenter I know leaves gaps for expansion / contraction. The only thing I can recall is letting drywall assume room temperature before installation. Look at all the trim in the house and I presume it was all butted up tight. If you are worried about gaps one could always use latex caulk to fill them.

[Ralph Mowery]

A lot of the 'floating floors' that are limanate or wood will be delivered a few days before they are installed. There is usually a gap around the edges that is covered by the molding strips.

[Clare Snyder]

With wood products you must ALWAYS leave expansion room or the floor will end up buckled

[Deguza]

The temperature gets down to 60 degrees during the winter (it is an unheated room), and during the summer could be 90 degrees.

[Deguza]

Well, we learned over the years a lot of things from each other. I am an engineer (ME) by training. Got my BS at an institution that emphasized rigorous math and science-based engineering principles, backed with mandatory shop experience (based on the German model.)

My buddy is trained as a fine furniture maker in Germany, and then worked both in Germany and France. Later he was a builder in France. I truly appreciate his skills, but sometimes cannot get him to understand the "engineering" side of things.

For example, a few months ago I showed him that an engineer can calculate the "sag" for a beam--one of the standard things you learn in a Strength of Materials course. He insisted that you can only do that with trial an error.

Another difference of opinion between the two us: I do my drawings using a CAD program. He does not see any value in that. He prefers the paper and pencil. I took two semesters of Engineering Drawing courses, two semesters of Machine Elements requiring design work, and a course in Transportation Technology, and designed an overhead crane, all with pencil and paper. Later many paper-based design work in the earlier days of my courier. I would never go back to those days!

Sorry I digressed!

Deguza

[Ed Pawlowski]

They stopped building bridges using the trial and error method a long time ago.

I too prefer doing drawings on paper. I do one every three years or so. It would take me longer to learn CAD than just do the drawing. If I had to do it frequently you can be sure I'd learn the program.

[dpb]

...

...

Shoulda' learned the FIGG Bridge Engineers about such stuff before the FIU collapse.

--

[Ed Pawlowski]

There has been a few. Science Channel has a series Deadly Engineering that shows some miscalculations.

Then you have Galloping Gurtie over the Tacoma Straights

[invalid unparseable]

Biggest problem with wood is moisture regain and lose with humidity:

[invalid unparseable]

I'm reminded of a screw up with a railroad bridge here:

Apparently they could not change the level of the tracks but had to raise the height of the bridge.

I am also reminded of a high school classmate here that was a civil engineer who when retired started working part time teaching at a junior college. Administration admonished him for flunking too many students and told him to let them pass. Would not be surprised to think that some of these dummies got hired by the state.

[Ralph Mowery]

A similar thing hapened to a friend of mine. He had a part time job at a junior college and was teaching basic electrical wiring for industries. Companies would send their people to that college and pay fot it if they maintained a C or better grade. He had taught other corses over the years like refrigeration. After flunking about half his students in the electrical class he was told his services were no longer needed. I think all the college wanted was just the money from the companies.

[invalid unparseable]

Not quite like that when I took a graduate level chemistry course as an undergraduate. I got a B in the course but the adjunct professor was going to give out D's to many young graduate students which would have taken away scholarships and had to give an easier final exam.

Years later the head of the chemistry department told me they went easy on young graduate students to get them hooked into staying but would tighten things later. Did not mean they would graduate. I saw it in grad schools. Professors would get their hooks into grad students to get R&D publications for their personal benefit.

I see it today. Universities love to have many students and rake in the cash but not all will graduate. They don't care.