What To Use To Make MDF Water Resistant....??

[Crow Horse]

I plan to make an MDF work surface for a Workmate that will be used outside and stored in a unheated porch. It won't come in direct contact with water but will be exposed to humidity swings. What can I use to make the MDF water resistant? I don't want to paint it. Any ideas?

 

[acer66]

Sounds like you have not bought it yet so waterproof mdf could be an option but it has limited availability and high prices afaik.

Medex® | Roseburg

www.roseburg.com

If that is not an option or you already got mdf.

How to waterproof MDF (Medium Density Fiberboard)

Forest Plywood explains two different approaches to “waterproofing” MDF so it can stay protected and withstand moisture in high humidity areas. Learn more!

forestplywood.com

 

[Dave455]

To be honest, you can’t.

I’ve used most types of manufactured board and I’ve pretty much decided I never want to use MDF for anything, ever.

I find it almost impossible to get a decent finish on it, even for interior use, and the slightest knock damages it.

For exterior use, I’d say no way. For exterior use as a work surface, definitely no way.

Almost any other sort of manufactured board will be an improvement, but I’d avoid chipboard too.

There is an “external” MDF, but rather than tweaking an unsuitable material, I’d rather use a more suitable one in the first place. The size of a workmate, a small piece of exterior, (or even marine) ply isn’t going to cost much.

 

[propmaker]

Shelac works well, use something oil based, not water

 

[alinc100]

Make your pieces out of MDO not MDF. Medium DensityOverlay is a paper faced product used often in outdoor signage.

Another thought would be Baltic Birch plywood and a spar varnish or Waterlox varnish.

 

[Crow Horse]

I looked into waterproof/exterior MDF. Pricey and not available locally.

 

[Shiftless]

Marine grade plywood would be the best

How about natural wood lumber? 1x8 or similar

 

[seber]

MDF is nonstarter for outdoor use even if water is not in direct contact. Humidity alone will destroy it.

 

[kd3pc]

seal the best you can with marine epoxy...will get you 8-10 months of use . Star board my fit your needs better. As they say above, you might best served with alternate base.

 

[nickelTwin]

I would use solid surface acrylic. The stuff used for countertops. Commonly called Corian. You can get scrap cutoff pieces from counter top fabricators for cheap.

I would not use mdf for your purpose in damp conditions

 

[dnschmidt]

Several companies make exterior MDF but normally they are only carried by large wholesale suppliers such as Hardwoods Inc. and you might have to buy 40 sheets at a time. I used MDF to make all of my furniture in my house and painted it with automotive urethane primer and basecoat/clearcoat with at least 4 coats of clear and then full polished it just like you do a car with a buffer. All of it was painted in pieces as the furniture is put together with Hafele MiniFix connectors and can be knocked-down. These are two cabinets I built to hold my audio cassettes and CD's.

 

[ybnormal]

as someone pointed out above, MDO is used for signage. I got some last year from a signage company that was selling it on Craigslist. what they were selling was used signs that the customers requested to take down since the housing subdivision was built and done.

first it has a special chemical painted on, then the vinyl sign is pasted for teh advertising. I've had mine sitting outside in the weather for the last year and it hasn't even come close to warping. they were selling it used for $15-20 a 4x8 sheet of 1/2" ply. and the 12ft 4x4s were free

usually this is where if it was a tool someone on GJ would say You ****

 

[alinc100]

usually this is where if it was a tool someone on GJ would say You ****

We in the tool zone would also point out the technicality ,"you cannot **** yourself"

 

[pbon]

What about that fake wood deck material as an alternative?

 

[dnschmidt]

MDO is fine but like waterproof MDF sort of hard to find. Here in Phoenix it's not a problem as we have very large hardwood sources in the rural areas you sure as hell are not going to find it at the local hardware store.

 

[superspec]

We got a sheet of 4x8 1” exterior mdf a while back to try out. Took a small sample and left it in a cup of water for over a day. It hardly changed at all.

 

[bonneyman]

I would use solid surface acrylic. The stuff used for countertops. Commonly called Corian. You can get scrap cutoff pieces from counter top fabricators for cheap.

I would not use mdf for your purpose in damp conditions

Slick idea! I'm gonna have to try that trick on a project.

 

[kaymccampbell]

How about Azek or Kleer PVC "wood"? You can get a chunk at the big box. It's not cheap, but you can leave it in a bucket of water for a few decades with no ill effects.

 

[tamaraw]

Consider marine plywood, or even better, something like marine HDPE. No matter how you treat or coat MDF, the material is vulnerable to moisture and will die eventually, just a matter of time.

https://www.tapplastics.com/product/plastics/cut_to_size_plastic/king_starboard/

 

[Skiff Builder]

I work with all kinds of sheet goods around the boat shop.
I'd use any plywood with a PS1-09 Exterior stamp.
BCX pine, ACX ( Arauco), Roseburg Marine A/B Fir, MDO (all D Fir core).

Tested them all by cycling through semi diurnal tides for last couple years. They all hold up.

Piece of CDX D Fir in back of truck is 4 years old-Outside 24/7/365

 

[gerlbaum]

Can Corian be cut with standard wood blades?

 

[WWheeler]

Applying a laminate to all sides will do it.

 

[Voi]

I have bought a few sheets of MDO from Menards locally but have not used it in the application you describe. I doubt it's as durable as the stuff I used to buy at specialized lumber yards some 30 years ago but I do like it. I don't believe there are Menards in New York but I'm sure you can find MDO somewhere.

But the exterior plastics sound like a good idea. Starboard makes a foamed interior product called Starlite XL, I believe. If it's anything like comparing solid PVC sheet to PVC sheet with a foamed interior it is probably significantly lighter and slightly more rigid than regular King Starboard. You can also buy it online in smaller or custom sizes. I assume you don't need a full sheet or whatever you use. But still likely more expensive than locally sourced MDO.

Of all the options mentioned I would start with looking for a piece of Starboard or Starlite in the size you need. If that's too expensive than look for MDO.

 

[honcho]

Earlier versions of the B&D Workmate had tops made from plywood which were superior to the MDF tops of later models. I think a marine plywood replacement that has been coated in polyurethane would work reasonable well but, being frugal, I would probably go for solid wood with polyurethane unless I had the marine plywood on hand.

 

[Bubba Fett]

I wouldn't bother with MDF for a workmate/work surface material. Even if it's coated, it will be vulnerable as soon as it is scratched, cut, or chipped. It would probably be fine inside a shop, but left exposed to the elements, it will get warped and uneven.

You could consider composite decking material, which should hold up well in adverse conditions.

 

[nickelTwin]

Can Corian be cut with standard wood blades?

Yes, and shaped with router bits like wood

 

[neophyte]

MDF is just the wrong material.
A work bench top will inevitably get nicked, and once water gets to the core material,
The MDF will expand.
Even major manufacturers like IKEA can’t figure out s good way to stop issues.

 

[WWheeler]

I wrapped my router table's 1-1/2" MDF in a 'scratch-resistant' formica laminate more than 25 years ago. That table has been used as a work surface and has seen tens of thousands of board feet of material run across it. I've completely worn out two routers, a 3HP porter cable, then a 3HP Dewalt, and it currently sports a 3HP Triton. It's survived several moves into new shops thousands of miles apart. I couldn't dare count how many drinks have been set (and sometimes spilt) on it in all that time, but the table is still perfectly mint and every bit as flat as my table saw top.

 

[Crow Horse]

Thanks for all the replies. I'll try to source some MDO as that might be the least expensive functional option. Plan B might be to make it from solid wood boards. I live in a very rural area and sourcing items locally is sometimes problematic.

 

[bigredcornhead]

What about that waterproofing membrane youre supposed to use for cement board, RedGuard?

 

[Chris_Hamilton]

Multiple ways to do it. Relatively simple way is to do one of two things. Sand the MDF with 180 grit. Blow off, wipe down, tack off. Mix up some epoxy resin and brush it on. It will soak into the MDF. Might need to do it more than once. Other way would be to again sand with 180 grit, blow off, wipe down, tack off, then spray 2-4 coats of epoxy primer on it. Ideally SPI Epoxy. Applied properly it will be water proof and since the SPI has UV inhibitors in it will last in the sunshine.

 

[Mandres]

I would try a piece of pvc trim board. It's available at the box stores and humidity won't bother it. Durability for a work surface might be questionable but it's easy enough to replace if it gets banged up

 

[KansasArt]

What about using advantech subfloor? Yes, very expensive for your use but I bet if you looked around at a new development going up you could find a scrap piece that would work.

 

[NoahG]

Jeldwen makes an exterior MDF product under the Miratec brand called Extira. We left some in a puddle for a few days and it didn't swell up. Just make sure you seal the edges and you're good.

 

[joe_pinehill1]

Unless you live in Southern California, MDF will not last outside. Maybe its a short term use and you can get by? Try MDO, or a marine plywood.

 

[Crow Horse]

Just to clarify, it won't be in direct contact with the weather, however, it will be subjected to humidity and outdoor temperatures. Think outside storage shed (unheated).

 

[lolaetype]

I plan to make an MDF work surface for a Workmate that will be used outside and stored in a unheated porch. I

I used it for a workbench top i applied coat after coat of clear poly urethane, including the edges until it stopped soaking in. It's been pretty durable, water just beads up on it. It took maybe 15 coats though. Looks good after 3 years.

For nasty, dirty, work I have a steel topped workbench. I use the MDF one for less rigorous work.

 

[sparkness]

dont use that material at all, use starboard or azek type material. Plastic's only, unless you like pain of repairing wood products that cannot not holdup weather. for example, do you a Wood boat or a Fiberglass boat?

 

[ZRX61]

Unless you live in Southern California, MDF will not last outside. Maybe its a short term use and you can get by? Try MDO, or a marine plywood.

I live in So Cal... in the Mojave Desert. MDF is a complete shitshow here too.

 

[tulowd]

Interesting thread. I have used hundreds of sheets of mdf over the years building high end car audio sound systems, from speaker baffles to subwoofer cabinets, trunk floors etc. The routing and sanding / finishing capability is second to none; also paint, glue and fiberglass stick nicely to it. I have never had anything swell up or come back because of moisture damage.

Truth be told, I have seen damaged/swelled mdf in a few places, including a 20 year old shelf unit I built that has sat out in the rain and now in my car shelter for about 5 yrs. It looks terrible, yet still manages to stay whole, lol.

Main Point: About 5 yrs ago, I sat next to a gent on a plane and we got talking. He was German, and since I'm fluent, we had a nice lengthy conversation including "what do you do for work". Turns out he was the lead engineer for a company that manufactures the presses that make ....gulp...mdf!

SInce MDF is primarily made of dust and glue, it actually contains lots of waterproof goodness. He told me in no uncertain terms that most higher grade mdf now manufactured is essentially moisture resistant, due to the improvements in manufacturing and some kind of outer layer/surface seal introduced during the pressing. The edges obviously are going to be potential entryways and could use a sealant.

IMHE, I would use plain 3/4 or 1" mdf (since it is and will remain dead flat) and replace the tops as needed. Anything that is used as a surface is essentially consumable to some degree, since once it is damaged/marks up the work piece it can no longer function for its intended use.

I have a 25 year old Black+Decker Workmate 200 that still has the orginal plywood surfaced combo top/vise intact, other than usage damage. I live in Toronto so we get our share of humidity, rain, winter and the other seasons. It does live in a heated garage, but it amazes me how flat and solid it remains after so much use in a tough environment.