Laying down 3/4 solid red oak flooring, have 3/4 inch plywood underlayment, and have a few low spots (1/8-1/2 inch by 6-12 inches). Do I fill with SLC? Will the nails still drive through this stuff?

Thanks,

--Brian

Not supposed to but I have done it on rare occasion. It can crack. I map the felt and avoid fasteners there or use an 18ga. brad nailer and blind nail over that spot. You can also cut out the felt a bit and use a bead of urethane subfloor adhesive there.
It would be best to avoid using a portland based patch and use some roofing shingles to fill it in.

Jerry is right , besides not being very good for your gun , you will just bust it up .. You can just cut some roofing paper instrips and feather it to the edges .. a 6 x 8 piece then a 4 x 6 piece on top [etc].

That sounds much easier, too! Thanks for the replies.

--Brian

I have to say, ARDEX SD-F impresses me, more and more. I can shoot right through a ¼" of it. It isn't brittle, but rubbery. It doesn't crack out like other portland patching compounds, like Mapei PlaniPatch(unless you add latex) It sticks to wood like glue.

Many are not willing to take the time to mix, screed, and let it set-up/dry completely out, to even try it. They need to get wood down to get paid, with little to no money into floor prep, so they will shim as they go, with what ever takes up the space.

I use them both to Piss coat a floor i am going to put Vinyl down , and i do add the latex .. and yes it takes a long time to dry with the latex in it , even with a fan blowing across the floor .. I just dont want to beat up my nail gun nailing through it .. Different strokes for different folks ..