Office chair mat-will it work on (soft) carpet?

I would just cut a bit of say 12mm ply or chipboard to go underneath. Might need securing to the chair.

I use them on a carpet (with underlay) and I have found that because of the constant deflection of the plastic chairmat caused by the pointweight load on the wheels (and around 19 stone of me sat on the chair) I have to replace the mat around every two to three years due to it cracking.

Before they get to that stage though, I must admit that they are useful and work (if a bit expensive from Staples).

I have broached the subject of putting a piece of 3/8" plywood between the carpet and chairmat with SWMBO and been given the very definate answer of "NO" (or words to that effect) - but if your cicumstances are different, then that may be an option for you.

Cash

Yes. See similar at Staples with small spikes underneath to stop them sliding around. I have two of them.

We had one from Costco, it was quite heavy duty thick plastic with small spikes underneath to stop it moving on the carpet. When we moved there were no marks from the office chair and the depressions from the spikes disappeared with a hoovering.

Richard

Lateral solution: use steel spikes of the kind placed under loud- speakers by hifi enthusiasts. They make a very small hole in the carpet backing and keep the wooden (I assume they're wooden) legs clear of the pile.

Not so good if you move the chair around a lot, though.

The Costco one is cheaper and better. Designed for 300lb Americans.

It's my daughter, and she cannot stay in one place for more than a second...

Great! Was looking for an excuse to pay Costco a visit for a while now...

The Costco one is excellent. I think it's been under my work chair for a couple of years now, and still looks good as new. It was under my exercise bike for a while before that.

Unfortunately, I took a small car with me and it doesn't want to roll up, and the spikes on the back had drawn blood by the time I got it jammed into the rear seat area of the car and the door shut. They're not very sharp, but they are hard.

There are two types of "plastic" (defferent types of plastic but I can't remember the proper names).

I used to use ones from Viking, but they cracked after a few years. I then found ones made of the better plastic from Staples, more rigid but still with the spies on the back. Much less creep than the Viking one and seems to be lasting better.

As someone else has said, it's more rigid and doesn't roll up, so trickier to transport.