So I would ask if the water you speak of will every fall directly on the mdf?
if so the not so good of a material for that
but I work in a non climate controlled shop and mdf will swell but if not in contact with direct sunlight or water you will not have issues
if you are worried you could go with a plywood but it needs to be a high grade plywood so that it is smooth and well most of those are interior grade and will de-laminate if they come in contact with water over time
you can get water proof mdf if you have a local wholesaler in your area
but I use mdf for all my table tops and I have no problems as long as they do not come in direct contact with water
No water will touch it. It comes in from the bottom of the floor on the opposite side of the basement. The floor is sloped to that corner. Whoever built it 115 years ago was thinking about water run off. The entire area where I live was landfill at some point.
If using some sort of sealer on the mdf, pay particular attention to the edges. When doing so notice how they wick the sealer up like a sponge. this will happen with humidity in the air to a minor extent.2-3 coats are recommended by yours truly.
I have had my edges swell by as much as 1/64" with the seasonal humidity jump from winter to summer. but once it swells it pretty much stays there, unlike natural wood which swings both ways.
As @RobertCanning states. you will need to do a skim cut now and then anyway mitigating any swelling issues. and a light recoat of sealer to the surface after a skim isnt a bad idea either.
I reside in the North East and my xcarve is in an unheated garage. I do get quite a lot of humidity issues. No problem with the MDF but I did notice some rust forming on my xcarve. Paint bubbling on the end plates that aren’t aluminum so watch for that problem in the future.
Not as big of a problem as you might think. Simply apply some Minwax 41700000 High Performance Wood Hardener to all the wood surfaces. Use at least two coats and you’ll be golden. Once you see how this stuff affects the wood you’ll understand. It’s like shrink wrapping the wood fibers. I’ve used this stuff for years and it works incredibly well. I was told about it from a guy who builds boats. Just make sure you use it in a well ventilated area, and don’t pour out more than you can use in 5 minutes time because it evaporates quickly. Enjoy.
That’s personal preference. The one I’m going to build will have stained hardwood over the 4x4’s, but whatever looks best to your eye is fine. One other thing that I almost forgot, do NOT use a good paint brush for applying this. You will never get this stuff off the brush, so you will have to throw the brush away after applying. Simply go to Harbor Freight or Home Depot and buy a cheap $1.00 brush (or two) to use for applying. Here are the full directions;
Here is my latest design. I added additional wood to the interior of the top and mocked up some side brackets as someone suggested that will help with rigidity. Going to take me a month to put this together…