I have a staircase leading to a 2nd floor hallway, both have 3/8" parquet that will be removed. The plan is to glue down new 3/8" engineered wood flooring in the hallway but NOT on the oak stair treads, yet rather sand & refinish the treads...This would increase the rise from the last stair tread to the top of new stair nose at the end of the hallway by 3/8".

In the hallway, gluing new 3/8" flooring to a 3/8" plywood underlayment, would further increase this rise to 7 7/8". The next rise down will be 7 1/2" and the rest of the rises below would be 7 1/4" - 7 3/8".

Thoughts or concerns here??
Thanks!

According to the IRC Stair building code:
The maximum riser height shall be 7 3⁄4 inches.
The greatest riser height within any flight of stairs
shall not exceed the smallest by more than 3⁄8 inch.

I would check to see how well that old parquet is glued down if your intending to go over it. I would remove it.

Thanks!
That said, how much of trip hazard OR noticeable would a difference from 7 1/2" to 7 7/8" be?

Thanks!
Yes, I intend to remove the parguet, in order to refinish treads and risers. It's not glued down as bad as I thought but the adhesive appears as if it'll be a struggle to remove as it's quite thick in some areas i.e. 2nd pic...Suggestions?

Use an oscillating multi tool to remove the adhesive. If you don't own one you can get an expensive one at Harbor Freight for about $15.00. Great tool....has lots of uses. Blades wear out fast and aren't cheap.

Noticeable isn't the problem but a trip hazard is. Lay the boards down and walk it. Codes exist for a reason. Also, if anybody ever tripped and an insurance claim opened and the insurance company investigated there could be a problem i.e. accident due to code violation.

How are the oak treads attached? Maybe remove them and put a piece of 3/8" plywood under each to get back to original dimensions?

Thanks! I'm still in planning stages so I can't say for sure how the treads are attached, until I get the rest of the parquet off at least one of them but that sounds like way too much work and hopefully, I won't have to attempt such.

I'm now seriously considering floating the new floor instead of gluing it down...
We shall see!

Since posting here, I've had a few local wood flooring stores out for glue-down installation proposals...Not one of them advised adding the plywood underlayment but rather just gluing the new floor directly to my plywood sub-floor.

Other considerations beyond the stair riser heights are that the hallway leads into the master bedroom, which is currently bare plywood sub-floor but I plan to run the same new flooring into the bedroom from the hallway.

As you enter the bedroom it transitions into the bathroom's old ceramic tile, which is level with the parquet in the hallway so, I'm assuming it's 3/8".

When I'm ready to do a full remodel of the master bath, in the future, I'd like to replace the old tile with new 3/8" porcelain that I already have.

Therefore, in addition to the stair riser heights issue, if I go as planned by adding 3/8" plywood subfloor and glue-down the new 3/8" flooring, then the new flooring will be 3/8" higher than the tile transitioning into the bathroom.

I appreciate all of your helpful input and advice!

Concerning your last item (new flooring will be 3/8" higher than the tile transitioning into the bathroom) cut a 15 degree bevel along the edge of the flooring to create a ramp down to the tile.

Thanks!
Sounds like a "hard surface reducer" might do the trick.

Whatever works and is to your liking.

Don't know what will work or if I'll like it until it's done...just thinking out loud.

That being said, after consulting several local pro installers, although not ideal, it appears glue-down installation to the plywood sub floor without installing a plywood underlayment is the way to go, therefore no stair riser height issues.

Also, it appears, if I want my flooring, especially from the hallway to the top stair nose to be flush, my only option is a glue-down installation not floating.

Somethings I've learned...
If I didn't mind ALL of the required transitions at EVERY doorway AND in between the L-shaped hallway AND if I didn't have the staircase to deal with, I'd likely go with the easier, less expensive floating installation.

To me, all of the required transitions are bad enough but the deal breaker is the required "overlap stair nose" at the top of the staircase, which appears to create a trip hazard going down the stairs.

Thoughts?

When you plan the "overlap stair nose" for the landing keep the following info from the IRC in mind as the overlap is a factor in calculating the tread depth of the step below the landing.
The minimum tread depth shall be 10 inches (254
mm). The tread depth shall be measured horizontally
between the vertical planes of the foremost projection
of adjacent treads and at a right angle to the tread’s
leading edge. The greatest tread depth
within any flight of stairs shall not exceed the smallest
by more than 3⁄8 inch (9.5 mm).
Also, there are state codes that supersede the national code so you might want to check your state code.

Thanks! I don't believe I'll be using the "overlap stair nose"...

At this point, since I already have it, I'm looking at potentially using the "FloorMuffler - Double Glue Down Installation":
[youtube]https://www.youtube.com/watch?v=pMGwgscPbh0[/youtube]

Talk about NOT taking the easy way out!
Helpful thoughts and feedback are greatly appreciated!