Talk to your roofer.

It is a fundamenta law of the unverse that all commercial nailers will use nails whose length is 3 times the thickness of what they are nailing to. Not sure about screws.

I've got 1-1/8 plywood sub flooring with nails sticking thru under the house at least 2 inches. Where's the sense of that?

Can you loosen the fixtures and let them hang down out of harms way? Then you can bend back any nails in the way or snip off the screws as needed. Cheap insurance. That's what I'd do and also maybe figure a way to slack the wires. Maybe disconnect them so they hang loose.

Thanks for the responses

Mxypix- Good idea. However, the ceiling under the roof is finished in wallboard, so there is no direct access to light fixtures and wires.

Renovator: I intend to talk to roofer. However I am trying to get an idea what to expect to make sure it is done properly, or if he does not know what to do to be able to suggest something.

Google >bonding pvc membrane<. i didn pursue it further than that.>That seems to be an alternative.

I got curious, kept looking, Googled >how is pvc membrane attached to the roof================

Adhered Installations

Product can be installed with Product PVC Bonding Adhesive for a fully adhered installation. Fully adhered installations are the answer for design limitations on mechanical penetrations of the deck or for situations where increased wind uplift pressure requirements must be met

Was it your presumption the roofer was using screws and nails? Maybe he wasn't at all. Even roofers know how to Google! (We hope.)

Based on membrane manufacturers recommended standard procedures the installation is as follows (after removing old metal roof):

1. Inspect, clean up, wooden deck (3/4 inch lumber), replace bad wood, remove or nail in old nails or staples, etc.
2. install rigid board insulation (polyiso rigid boards 1-2 inches thick) using 3 inch metal plates and screws (about 16-20 per 32 square foot sheet). [THIS IS THE PART I AM WORIED ABOUT]
3. Sometimes a cover board (such as 1/4 inch plywood is installed on top of insulation. In this case I guess the 3-inch plates go on top of the cover board and screws go through the cover board > insulation > and deck.
4 As msyplx said, PVC membrane is glued down with a special adhesive on top of cover board or insulation. Seams are heat welded with a hot air gun.

Based on membrane manufacturers recommended standard procedures the installation is as follows (after removing old metal roof):

1. Inspect, clean up, wooden deck (3/4 inch lumber), replace bad wood, remove or nail in old nails or staples, etc.

2. install rigid board insulation (polyiso rigid boards 1-2 inches thick) using 3 inch metal plates and screws (about 16-20 per 32 square foot sheet). [THIS IS THE PART I AM WORIED ABOUT]

3. Sometimes a cover board (such as 1/4 inch plywood is installed on top of insulation. In this case I guess the 3-inch plates go on top of the cover board and screws go through the cover board > insulation > and deck.

4 As msyplx said, PVC membrane is glued down with a special adhesive on top of cover board or insulation. Seams are heat welded with a hot air gun.

Step 2 is what worries me.

There seems to be a difficulty for every solution. :-)

Glue it all together and hold it down with 5 big stones?

Leave the metal roof on and use magnets?

Sorry, couldn't help it. :-)

Love it. I think you summed it up very well, and helped me lighten up on this problem. I did speak to the roofer and he will size it up again when he gets here and probably use different length screws. It may take an extra hour or so, but he is willing to work it out.

Now we are delayed because of rain. Will keep you posted.

Thanks all.