Two things. Is the meter accurate? Im not saying yours isnt but when i do a reading i always like to double check. Because the meters Can go outta whack and need adjustment. Now assuming the meter works in good fashion. You said water pipes are 20ft away that doesnt matter. If you have a leak water can travel. If you had a full blown leak youd know but condensation over time could cause the same issue. Pet stains in theory could get your high reading if the pets urinated in the area fairly recently. But you are left with two scenarios. One you get some fans out and let the floor dry out for a week and then retest. Or you rip up the floor in the area and inspect the subfloor. Was your floor cupping? Why did you start sanding?

Thanks John for your response. I have enjoyed your posts over the past 2 years. I can put the citralic acid on the boards, but will I just be brightening the gray wood? The gray didn't seem to come up with just the EFC. The "tinted" boards were stained last year, but are mostly in the shade and still look pretty good. The problem is that they are only half of the porch, and the other half is the grayed new untouched garapa that is in the full sun. I wanted to stain both with woodrich wiping stain and have them look the same. Will the HD-80 strip the tint off the boards, so that they will not look darker than the new boards?

What type of look are you trying to go for? If you want to keep Garapa looking the same I have a product called Wood Protect. It's 100% invisible. Water-based. Zero VOC's. Will last 5-7 years depending on traffic. UV inhibitor. Lowers the surface temperature about 7-10%. Simple pressure wash will clean it, actually, since it bonds to the wood at the molecular level, all you need to use is a garden hose to clean it. Also, because of traffic over the years, you can spot treat it. No need to strip and reapply. Kinloch is the manufacturer if you'd like to check it out. We're working on a pigment in case you are looking to darken your material, but that won't be out for a few more weeks.

This year I hope to make some progress on the basement. I am waiting for the quote from the contractor regarding my bathroom. I think I'll email/call him today. That will be done by summer. I took out one of the fluorescent fixtures in the basement and the stupid junction box is on a joist perpendicular to the floor, so no way can I install a new fixture. I'm not moving a junction box! A guy at work can though, so I need to clean up down there a bit and I'll get him to come over and move it. There are two more down there, so I assume those are the same. I am just putting in inexpensive track lights from Ikea until we can get things going down there. For the immediate future, I need to get the basketball hoop set up so another guy from work can help me put that up. I need to replace the one we have, because it's broken, and this one we will mount higher. Yard work is never ending of course, but the weather has been less than pleasant for that on my days off. Days I work are beautiful of course. I'm still training for my 15k in Toronto in 3 weeks. Yikes! I think I'll be ready. I have no grand illusions of finishing in a great time. I just want to have fun. :)