I ended up doing MDF tops for my workbench (1" MDF over 3/4 plywood), and finished them with shelac for a protected, low-friction surface. It is still vulnerable to water damage, but not as bad as unfinished, and as a spoil layer it's not bad. It has plusses and minuses.
Seconded! I recently built a large 50" x 90" work surface in my garage and used MDO sign board (another phenolic resin product, not much more expensive than MDF and available at many construction-oriented lumber yards) for the top surface over top of a hardwood plywood subsurface and heavily milled Douglas Fir legs and trusses, all doweled and glued together. I've been quite happy. It was easy to use a router on to make channels for t-tracks, and has been quite stable for the past 6 months or so through the fall, winter, and spring weather changes with only an oil-filled radiant heater to keep things from getting too frigid.
Unless there is a drop of moisture, then you throw it all away.
You might not want to set foot in your kitchen or bathroom then. Generally speaking cabinets (in the US) use particleboard frames. Higher end stuff will use plywood.
I went with IKEA's Sektion cabinets to replace some forty year old particleboard cabinets that warped after years of water damage from a burst pipe. They came with a twenty-five year warranty so there's clearly some expectation of longevity.
Those are normally coated in melamine, even the edges, hence the ability to use them in a wet area. Ironically standard worktops are only coated on the top, so those can take damage.
I could be wrong, but isn't MDF basically made from the waste of wood products? I mean, it's graded and standarised. But MDF _is_ the waste. So to waste it again is no great loss.
But as with all things, I'm certain some producers are using raw/virgin materials. Probably from wood that is dirt cheap.
MDF is an engineered product comprised of homogenized hard and soft wood pulp, binding agents. It is dehydrated and pressed together to create a material that is of higher density than fiber board.
The amount of sawdust needed to create a sheet of this stuff is astronomical compared to the output, not to mention the manufacturing process being very resource intensive. You also cannot just take bags of sawdust from the wood mill - it must be macerated and ground to a very fine dust with roughly the consistency of flour.
The main advantage it has is that it is heavy (to weigh down furniture) and very easy to cut with bandsaws, mills, lasers, etc because of its uniform distribution of its constituent parts. It’s also good for applying vinyl wraps and edging which is one reason why arcade cabinets are often made from it.
All this for a product that is roughly the same price as A cabinet-grade ply:
...which means MDF is fine if it's entirely clad in a few mm of something more water-resistant, with the MDF just serving as structural infill. (This is how most kitchen cabinetry is made. And they put up with the steam from a pot boiling below them just fine.)
Our kitchen countertops are MDF covered in some sort of laminate. The laminate is great, but the MDF is swelling over our dishwasher and looks hideous. I'd be careful near moisture even if it's covered.
MDF for structural anything? That seems surprising, it's really weak and prone to sagging, and quite heavy. It's about the last thing I'd want to hang on a wall.
Unless there is a drop of moisture, then you throw it all away.
It’s so depressingly wasteful.