[clairity]

no, drywall is basically chalk sandwiched between paper and provides no structural strength to a wall. studs provide compressive strength while plywood provides shear (and some impact) strength to walls. metal strapping is usually added to provide tensile strength. plaster is backed by lath (wood slats), which provides some shear strength akin to plywood backing.

[lazide]

Bwaha, that’s just not true.

As long as the paper is halfway intact, drywall is very difficult to remove and provides significant strength to a wall. It’s a composite material, and excellent fire barrier.

It’s really obvious when it’s up compared to not.

It’s not as much as lathe and plaster, but lathe and plaster is extremely difficult to work with in every other way, and far more labor intensive.

Plywood on a wall is important for shear strength, but lathe and plaster doesn’t replace it. Properly designed earthquake resistant shear walls became a thing long after lathe and plaster were phased out.

[clairity]

i probably overstated my point by saying drywall has no shear strength, but we seem to agree that drywall < plaster & lath[0] < plywood in that respect. i'd suggest you've also overstated the strength of drywall as "significant". it's not nothing, but against an earthquake, it's approximately nothing. plywood backing, of course, is the minimum required by code for earthquake resistance.

plaster & lath is harder to work with, but has many superior qualities (re: moisture, sound, heat, malleability) that it makes it worth it in many residential cases (not so much commercial, where reconfiguration is more frequent).

[0]: a lathe is a machine tool

[lazide]

Depending on thickness and stud construction, drywall has higher calculated shear load than lath and plaster -

https://up.codes/s/shear-walls-sheathed-with-other-materials

There are easy to install drywall elements (heavier drywall, or sound deadening backing sheets) that also cut down on noise.

As with all things, ‘it depends’. Lath and plaster isn’t used much anymore because the cost rarely outweighs the benefits.

In non-seismic shear wall usage, it’s allowable to use either.

(Edit: fixed my very persistent autocorrect from lath to lathe - doh, thanks for noticing that)

[bombcar]

Or what you often find in residential construction, lath and plaster under drywall hahahaha (I die now).

[clairity]

that sounds to me like a (bad) renovation. what really sucks is damaged plaster & lath being ripped out and patched with drywall. that's the worst of both worlds, since you don't get the seamless barrier that is plaster or the ease of use of drywall.

[bombcar]

Oh god there's so much bad renovations everywhere. My kitchen is technically an addition so one wall is: paint, drywall, wall paper (4 layers), lath and plaster, exterior cedar shakes, shiplap, and finally studs.

[lazide]

Beautiful. Part of why that happens I think is everyone is afraid to peel a layer off for fear of what they’d see underneath. A lot of contractors try to avoid renovations because it’s a never ending series of pandora’s boxes.

My favorite when checking out a potential house purchase once was a small wet spot in the middle of a wall.

When I pressed on it with my finger - and my finger went right through - into live termites!

That finger press probably saved me $75k and months of headaches.

[engineer_22]

It's considered rude to laugh at an interlocutor's comment.

You could bring an example of code or calculation instead of anecdote to demonstrate your point.

[lazide]

If someone asserts that water flows uphill, I dare say I do not owe them maps of the local space time curvature.

If that makes me rude, then feel free to downvote as desired.

[engineer_22]

I was going to agree with you, as a university trained engineer it seemed absurd to count drywall towards structural calculations, but then I did some research.

TIL gypsum board is given some shear strength credit in the code books:

https://up.codes/s/shear-walls-sheathed-with-other-materials

I wouldn't have guessed it, I wouldn't trust it if it was close to failure, but there it is.

I think the least attractive aspect is how drywall fails catastrophically, and once it's broken the strength can't be restored. This is probably why I didn't expect it to be counted in structural calcs.

[CamperBob2]

Weak elements secured in multiple places become strong ones. Potentially extremely strong ones.

The workbenches in my shop consist of multiple cheap, crappy pressed-wood folding tables from Office Depot, secured to each other on multiple sides with equally-cheap metal brackets. You'd think this would result in a rickety, unsafe platform that would blow apart in a stiff wind or buckle under light vertical load, but instead they are stouter in all three dimensions than most actual retail-grade workbenches. (And I don't have to feel bad about drilling into them!)

I can see drywall working exactly the same way, given enough studs and enough nails. The problem to be solved -- and the lesson I learned when I hacked these workbenches into existence -- isn't necessarily insufficient rigidity, it's too many degrees of freedom.

[bombcar]

Yeah, I wouldn't really count it for much on actual load bearing walls, but it is noticeable on non-load bearing walls, they become more stable with drywall.

The most noticeable place I've seen it is in garages; the ones that are drywalled on the inside don't seem to lean as much as those that aren't.

[clairity]

well that's good to know! i had an implicit assumption of load-bearing walls in my prior comments, which is why they skew the way they do. of course for non-load-bearing walls, drywall is perfectly fine, but i'd still choose plaster & lath (backed by plywood for seismic reasons) over drywall.

for a dream home, i'd love steel or mass timber for the exterior framing to reduce (maybe eliminate) interior load-bearing needs, so that interior layout is maximally configurable while still allowing lots of windows. expensive, but dreamy!

[SkipperCat]

Drywall does provide structural strength. While it may be easy to to punch a hole in drywall, it is very hard to cause it to fail via shear. Think about a square made of wires. You can push on it and the joint's angles will deform from 90 degrees.

Now, if you nail a piece of cardboard to the square, the corners will stay square when force is applied because the cardboard resists that force. You could even use paper and get the same results.