Wood screws for jarrah floorboards

I am laying 19mm jarrah floorboards on 19mm battens (due to space limitations). I was hoping to use secret nails/staples but I just found out today that the boards are not suitable for this, not the right cross section. I have no alternative but to "top-fix" but there is not enough space for nails. I want to know if anyone has experience with wood screws, I want to use 35mm screws such as found here:
https://screwsandfasteners.com.au/solidflooring
- Any comments on whether it can be screwed 3mm below the top to allow for sanding?
- Are pilot holes required?
- Strong enough?

I am a big fan of the German made Spax screws. Been using them for my outdoor projects. I am quite sure you would need to pre drill the holes in Jarrah and that they will be strong enough. The screws have a milling head and will probably drive below the surface if you give them a bit extra drive.

My local timber supplier is the biggest seller of Spax screws in Australia and as a result he got invited to Germany by them to celebrate their 50th anniversary of making screws.

no doubt it will work, but will it look OK?

after sanding, the screw heads will be 0 to 2 mm below the surface and the holes full of sanding dust.
If using 30 mm screws and plugging the screw holes is not and option -- and plugging a room's worth of counter bores would be a huge job -- perhaps use brass screws and aim for the screws to be just below the surface so that their heads end up level with the sanded floor.

Thx to the replies above. I had not received a notification for some reason and thought there were no replies.
By the sounds of it, the screws are strong enough, this type or the Spax.
@ian, with regard to the sanding dust, I can use a vacuum to clean this, right? And would plugging the holes with putty be a huge issue because nails holes are also filled as well, or is it because there is much more volume?

Thanks to responses above. I think I'm having issues on this forum as I didn't get notification of posting and I just replied before this and it didn't show up.
@Kidbee, I assume the Spax screws you have used are the same as the ones on the website I posted.
@ian, with regard to sanding, I can just vacuum this right or am I missing something? Also with respect to the plugging, is this a huge job because of the volume of putty, compared to nails?

Also, I noticed on the Spax website, that screws are secretly fixed on a timber profile like I have, where the top is not recessed.

Floorboard tongue & groove screw - SPAX
See bottom picture here.

I though it would have to be a profile as per attached sketch? Any comments on this. Do you think I can consider secret fastening again?

I keep having problems on this forum.
Have replied twice but not showing.

I would rather use nails than screws. As Ian noted, the screws are large and will show. Nail holes will disappear, especially if you fill them.

Regards from Perth

Derek

Hi
Thanks for the replies ... but I keep having problems in posting.
@Kidbee, are the screws in post #1 the Spax brand?
@ian, with respect to sawdust, can I use a vacuum to clean or am I missing something? Also is the plugging difficult because of the volume of putty?

Also I noticed on Spax website that secret fixing is used on timber profile similar to mine.
Floorboard tongue & groove screw - SPAX
See last picture.

I thought it had to be the profile in the attached image.
Can I go back to secret fixing?
What do you think?

@derekcohen
Thx for responding. Is there a nail which will suit 19mm battens? Top nailing that is. I can't secret nail on the profile I have.

hi Tech-Art

when I redid our kitchen floor 20 years ago, I secret nailed most of the boards, and screwed 4 of the boards.
I counter bored the screws -- which means I pre-drilled so that the screw heads finished 4 or 5 mm below the unsanded surface.
I then plugged the screw holes with timber plugs that matched the grain around the screw holes as closely as possible.
After the glue set, every plug was trimmed flush with the unsanded floor.
After sanding and applying a Tung Oil floor finish, the screw locations were mostly invisible and have stayed so over the intervening years.

My warning to you is that counter boring and then plugging every screw hole for a floor is not a trivial exercise.

IMO, putty or another sort of filler will stand out against a clear finished floor. Your options then are to make a feature of the screw locations -- possibly by using brass screws sanded flush with the floor surface -- or to live with what might look too much like a botched job.

Secret nailing or skew face nailing might be a better option as the much smaller nail holes are more easily hidden by putty or sanding dust and finish.

@ian
Thanks for the input, I did see something on Youtube on timber plugs just before your post. Interesting.
I think I will now go back to secret fastening. I've sent an email to Spax to confirm if the screws can be used with the secret fastening detail. If not, I will have to convince myself of secret nailing, but I just keep thinking the jarrah will break off given I have the wrong profile (see attachment). Screwing with drilled pilot holes feels safer to me than nailing. All the jarrah members seem to have different characteristics, some are so brittle and behave like ceramic, others are a lot more forgiving, like rubber.
Skew nailing ... I had not though of this before ... I will research this.

I have secret nailed T&G flooring with standard profile not secret nailed profile using a paslode fixing gun both air and cordless without any problems. I use 2 nails per joist near each side of joist and angled towards the centre of the joist. I also use drywall stud adhesive under every board as well, never had a single complaint/call back to any of them and they are as solid as a rock. Some floors were cyprus and have done 2 jarrah floors as well.

@rwbuild
Thx for your input.

I would look very closely at the secret nailing option. You would need to purchase, borrow or hire a secret nailing gun and the name is a little misleading in that many of them actually use staples (big ones). They look cumbersome but really are the easiest thing to use (except right up against a wall).

They look like this:

Attachment 418133

They are activated by hitting the "button" with a large hammer, which is normally supplied with the tool. This both moves the floor board into a tight position and activates the nailing process. Recommended. I haven't glued as well like RWB, but I think that is a very useful refinement guaranteeing zero movement or noise.

The price range is varied. This was one of the cheaper versions just from a quick glance, but I have no knowledge of it:

NEW UNIMAC Pneumatic Flooring Nailer Staple Gun Floor Gas Nail Cleat Stapler

Regards
Paul