After my 3 year old managed to open a gallon of paint and decorate our carpet 1 day before our house goes to market, I decided to install some engineered maple that I got a good deal on. As I pulled my carpet of course there was particle board. As suggested on the forums I began removing immediately. Here is where the trouble begins. Below the thin layer of particle board is another underlayment of 3/4" particle board of a much different and I suspect older design. I figured, no big deal, I'll pull that up too and throw down some CDX or OSB. 1.5 hours, a few scars, and 0 energy I got 1, I repeat 1 of these 3/4" particle board sheets up. They are nailed down into the subfloor and the board crumbles much sooner than the nails lift out of the board. In some rows the nails are as frequent as every 6" with rows every 12". In my instruction manual it lists and I quote-

STAPLE-DOWN OR GLUE-DOWN:
• PREFERRED:
3/4" (19 mm) CDX grade plywood
3/4" (23/32") OSB PS2 rated underlayment
MINIMUM: 5/8" CDX grade plywood
• Existing solid wood flooring
• Vinyl, resilient tile, cork flooring
• 3/4" chip, waferboard, particleboard

I am stapling. And praying that perhaps I can leave this bottom layer of 3/4" particle board as an underlayment without forever feeling guilty that whoever buys my house is getting the shaft and will have to replace their floor in 5 years. 6 years I might be ok with and perh as it is a starter home after all.


I've attached a visual. Let me know recommendations, and possible consquences if I choose the easy road.

http://picasaweb.google.com/lh/photo/-Ow7wDJRc3TXVhCXjfg1rw?authkey=Gv1sRgCMi7jLe-5diquAE&feat=directlink

Ofcoarse we all know that NWFA does not recommend mechanically fastening over particle board.
That being said....

Years back , I had quite a little clientele going in a mobile home park.
After disclosing my concerns, the customer's opted to go over the existing particle board. I had them sign waivers.

The result....I have done quite a few successful staple down installations over 3/4" particle board in mobile homes, ( installing 3/8" and 5/16" solid ).
7 to 10 years have past, sometimes no news is good news. I'm still in contact with a few of the customers, and the floors are still performing great.

There are different grades of PB I read. Some acceptable to fasteners more than others.

For some adhesive manufacturers PB is acceptable underlayment to glue over. Course, screwing and gluing ply over it would be the best scenerio/

Update:
Ended up pulling out the PB because it was only 5/8" and I had 3/4" plywood down in the kitchen and dining room already. Took me all day and actually I'm still going but my hands need a break from the crow bar. I've got a system using a grid pattern and a circular saw as well as a hole saw in harder to reach places. I can get a board up in under an hour now.
I'm putting down 3/4" T&G OSB as thats all that Home Depot had in 3/4" short of $40/board plywood. One question, should I use the Aquabar paper both above the plank subfloor AND above the OSB underlayment? If not both, which would be the preferable location?