I'm installing hardwood flooring on our stairs per the instructions on this site. I get to the 4th step, and after installing the riser, I see that the stairnose doesn't seem to want to lay flat. It wobbles like a table that you need to put a matchbook under 1 leg. After looking for a while at the step, it looks like the front of the tread on one side droops down a bit, maybe 3/32 to 1/8th of an inch. Enough that it can't get a solid footing and will most likely squeek in the future. Might have gotten into this pickle with some overzealous sanding.

I can get it level if I add a couple small shims to a front corner under the stairnose, but was wondering if that was a good idea. Would it be better to try to level out the drooping part by adding some wood filler to the low spot. I'm worried that over time, the pounding on the stairnose from normal traffic will tend to pulverize the filler. If filler is OK, is 1/8th thin enough to do it in a single application, or should I try a couple thinner coats?

If shims are the right approach, then do I need to add multiple shims along the front of the step, tappering them down to nothing where the tread doesn't drop off (about a foot from the side of the tread), or should I just add enough shims in the corner to get the stairnose to lay flat?

I don't want to try and sand the rest of the tread down, I think I'd have a hard time getting it to be reasonably flat, especially given the confines of a built-in stair.

Thanks...

Load it with liquid nails construction mastic. Or shim it with folded felt paper and glue it with liquid nails.

You are gluing and fastening the stairs, aren't you?

Old shingles work well too. Do not use wood filler once dry it will become brittle and will disintegrate under wear.

Yes I am gluing, I was just thinking that the gap was big enough to warrant something more solid than liquid nails.

Folded felt paper, hadn't thought of that (although I used that technique to raise a couple minor low spots on the living room floor when nailing). Just curious, any reason that felt would be better than wood shims?

KLS - that's why I asked first before using wood filler. Thanks for the responses.

Oh, this is a big gap!

Yes use wood shims. I thought is was just minor rocking.

Shims are the way to go here. Make sure you glue them down and to each other. I use bostiks best for all my staircases. Liquid nails will do the trick but I prefer fewer nails and using a good urethane adhesive allows me to do that.

I once had to remove a damaged tread a day after I installed it with bostiks best, I straightened a heavy duty pry bar and broke the head off 2 hammers trying to remove the 1 1/16" thick tread. It NEVER lets go. Worth every penny.