Does raising the height of a sofa compromise it in any way?

I have three inch feet on my sofa. If I replace them with eight inch feet does that in any way make it less stable? The weight should still distribute the same way, right? From the perspective of the couch’s frame, does anything change?

The couch doesn’t know how high it is, only that it’s weight is distributed on four points.

The important thing is that the new legs are attached solidly and so that the weight goes straight down into the completely vertical leg. If it is angled out or loosely attached, that changes the way the force is supported by the leg and can cause the leg attachment point to fail.

That’s what I figured.

But if I continued to raise the height of the couch, it would eventually become unstable, right? Is it because the legs eventually can’t support their own weight if their circumference and material remain the same? Or is it something very complicated about gravity and centers of mass?

If we’re being very pedantic, does the couch in fact get a tiny bit less stable with a five-inch increase in height?

What do you mean by “stable”?

If you increase the length of the legs there are three ways in which we can say the sofa is less stable.

[ul]
[li]The sofa becomes slightly easier to tip over. Think tumbler vs. highball glass. Or a book lying flat vs. standing up.[/li][li]If the legs are replaced with almost identical, but longer legs, they have a slightly larger risk of breaking. Multiple factors contribute to this.[/li][li]Any twisting forces in the joint between couch and legs increase with increasing length of the legs. Not likely a problem since it will usually be designed with no twist to start with, but extend the legs far enough, and twisting becomes unavoidable.[/li][li]And if you don’t have replacement legs, but just extend the legs somehow, any and all joints are at risk for those latter instabilities.[/li][/ul]

I would say yes, because the stress on the legs is not entirely vertical. Every time you sit down and lean back there is a certain amount of horizontal stress - more so if there are kids jumping on it or you and your special someone occasionally engage in amorous activities. Even shifting your position creates some front-to-back or side-to-side stress. A spindly leg would also be more susceptible than a block-type leg.

Rising the legs increases the shear or “racking” force on them. Couches get a lot of shear - when you sit down, you push the couch horizontally. If the legs are not very securly attached and braced, they will eventually loosen up.

ETA: or, what Bayaker just said.

Rather than raising the couch with longer legs, how about suspending the couch from the ceiling? Easy to vacuum under the couch, or make use of that area for storage.

Or raise the floor to meet the legs (i.e. put blocks under the existing legs).

But that’s a different question. There’s a difference between longer legs compromising and longer legs making it unstable and/or breaking due to their length.
FWIW, you’re not going to be able to raise the couch high enough that it tips over and still have it be usable. And as far as the legs being able to hold the weight, that’s a function of their strength. You could lower the couch so it’s only an inch off the ground, but if you use Popsicle sticks, you’ll have issues.

I lowered the floor, at least that way the couch doesn’t swing.

Swing? I’m picturing rigid metal poles securing the couch to ceiling joists.

There are commercial products sold for raising the height of chairs, beds &etc, in particular for the elderly and disabled. You can be sure that they would not be selling them if they were in any way dangerous.

This is a link to one company that distributes them - there are many more.
https://www.livingmadeeasy.org.uk/chairs/individual-chair-raising-blocks-1153-p/

I had neglected this; forces on the legs from the entire couch twisting (doesn’t seem likely) or from forces on the couch in the horizontal plane (sitting down, moving the couch, which are very likely) would apply greater torque to the legs. Going from 3" to 8" could make enough of a difference that it matters. It also depends on how the legs are attached.

Well that’s no fun. It would be a lot more entertaining to hang it from cables and convince your drunk friends that they just have the spins.

ETA, on second through, I don’t want to clean up puke that looks like it came from one of those pendulum toys.

Make sure your blocks have a big base and the legs of the couch are firmly secured to the (e.g. indents on the block) as small movements, especially sitting down or setting up from the couch will cause it to shift ever so lightly every time.

I used to have my futon couch on 8"x8"x16" concrete blocks and I had it fall off one of the blocks a couple of times. Whether it was minor earthquakes or my sleeping on it (in the folded position), it would slowly creep off the block over time.

Make sure your blocks have a big base and the legs of the couch are firmly secured to the (e.g. indents on the block) as small movements, especially sitting down or setting up from the couch will cause it to shift ever so lightly every time.

I used to have my futon couch on 8"x8"x16" concrete blocks and I had it fall off one of the blocks a couple of times. Whether it was minor earthquakes or my sleeping on it (in the folded position), it would slowly creep off the block over time.

If the OP is actually going to do this, I’d suggest bed risers that are specifically meant for dealing with these issues, provided it works with the size of the feet.
https://www.amazon.com/Home-Adjustable-Risers-Furniture-Heights/dp/B00MH74S16

My sofa has feet like this, so all I need to do is buy replacements with the same size screws.

I had a weird image in my head of the couch for some reason sagging in the middle if I increased the height, and it was nagging at me even though I knew there was no reason why this should be the case.

Thanks for the help, everyone!

Unlike couches, bridges are designed to push outwards with their feet, and if their feet aren’t held together by their abutments, the bridge will sink in the center.

Couches should be more like roofs: held together by rafters, to stop the walls spreading out and the center of the roof sagging.

A couch is supposed to work ok on a slippery floor: you would be disappointed if it cracked after a while because the feet splayed, or if it tore up your carpet because the feet splayed. Still, the feet will always splay a little bit, the couch will always sink a little bit in the center, and if the stilts you put it on are too long and thin, even the minimal splay would cause problems. (But if your couch is decent, you would expect other problems long before then).