What's the minimum staple length (and crown size) you'd use?

Manufacturer recommends 1 1/2 min to 2" long staples

Flooring is engineered 5/8

Subfloor is Advantech 23/32

Radiant heat tubing stapled up below Advantech

All replies appreciated!

You can safely use the 1&1/2" staples for a Bostitch M111 FS. You need to verify the the staples will not protrude through the subfloor and hit a tube. Do this by taking a piece of the subflooring and stapling a board to it. Then check if the staple has penetrated through the bottom of that piece of subflooring. Try multiple times. The idea is to make sure you will not protrude. If it does, then you will need to add some more plywood to the subfloor. I'd suggest 3/8" CDX. Normally, I'd recommended stapling that down but in this case, you will need to glue it and use very short saples to anchor till the adhesive dries. OR, try a Spot Nails that cab use 1&1/4" staples. Those staples are shorter and skinnier, 18 gauge I think. Or, glue down the engineered flooring!

The manufacturer says 1 1/2 minimum and 2" is the recommended length.

So, if the shorter staple you mentioned is used is their a risk of marginal holding power that could cause the dreaded "snap, crackle & pop" problem?

And, isn't it risky to use shorter than what's recommended by the manufacturer anyway?

Thanks again for your comments.

Anyone else have something to add? Is the glue down method actually the better choice here?

That 1½" staple will hold and is all that is really needed for ¾" thick flooring. the 2" staples are really for 33/32 flooring of days long ago.

Thanks for the reply.

You feel that the 1 1/2 will hold but am curious about the earlier post that suggested the shorter 1 1/4.

We've seen such a failure with shorter than recommended staple length.

Any thoughts?

Additional Info:

These are 5" wide planks.

If it fails with a 1¼, it will fail with a 2". When wood swells, nothing stops it!!!

Thanks for the reply but I'm not clear as to the "wood swells" comment.

There is no indication of swelling, cupping, or gapping with the floor.
Could you please elaborate?

I have never heard of a 1-1/4in staple for use with 5/8. 1-1/2 will not punch through Advantek.

The vertical movement. They would have had to use some real short staples, say 1" on the 5/8, over a low spot, in the subfloor.

Glue coated staples, like the Spot Nails 1¼" are, have tremendous holding power. You figure the angle the staple goes in. But wait it is not penetrating the whole 5/8" only to the top of the tongue. My calculations show the 1¼" staple, protrudes into the plywood almost ¾ of an inch, but at an angle, which is plenty of holding power for a properly acclimated engineered floor, over a flat substrate.

Either the flooring is buckling("snap, crackle & pop" floor with vertical movement) Did you check moisture content of the subfloor and flooring to be sure they were pretty close???
Or... there are low places, or bridging high places in the substrate, out of allowable specifications("snap, crackle & pop" floor with vertical movement)

Thanks for the replies.

It looks like uncoated staples were used and a combination of not checking for good flatness on the floor plus the short staples might produce the problem.

Any other views are much appreciated!