How to fill gap between floorboards and threshold?

[capital]

I had new sliding doors put in and a new threshold installed on all doors that the doors sit on. The gap between the thresholds and floor boards is 5mm at its thickest (apart from the big missing bit on Door 2).
Looking for some ideas to fill the gaps. I am not keen on gap filler as it needs to be very flexible (cops full sun for a lot of the day and gets cold at night) and handle traffic. Most of the gap fillers also say <3mm gaps.

I was looking at I/N: 0083890 or I/N: 0083866 and attempting to cut it length ways as it needs to be no more than 19mm wide as that is how thick the pine floorboards are. I would also need to get rid of the rounded edge on one side. I could probably expand the floorboard/threshold gap to 5mm all the way along with some chiselling.

Any other easier ideas please?

Door 2Door 1Door 1

[JacobZ]

Hi @capital,

A warm welcome to the Bunnings Workshop community and thank you for your question.

Is there any change in height between the new threshold and the floorboards? It's difficult to tell from this angle.

The simplest solution I can think of is to use Liquid Nails to glue either QEP 25mm x 2.5m Transition Cover Trim or a Metal Mate 25 x 25 x 1.6mm 1m Aluminium Tee Section in the slot. 

Alternatively, you could cut along the floorboards to open the gap up to a minimum of 10mm the whole way along and slot this Porta 50 x 30mm 2.4m Tasmanian Oak 'T Rounded' Astragal into the gap and glue it with liquid nails.

Allow me to tag @Nailbag, @Noyade and @Dave-1 for their thoughts.

Jacob

[capital]

There is probably a 2mm rise from the floorboards to the threshold.

The two metal options are a good idea, as long as there is some flex in them and I could use a rubber mallet to bend one of the sides down to meet the slightly lower floorboards, or flatten against the threshold.

I really wanted to avoid opening the gap up more as it would be pretty tricky. Door 1, which has the floorboards butting up against it, has its joist nails very close to the gap. It would also be an awkward cut with a multitool (unless you can suggest another tool) to evenly widen it to 5mm all the way.

Do you think I would have success getting something like the edging bead mouldings I mentions in my original post, hammering it in and then trying to knock off the excess with a hammer or chisel and then sanding down?

[JacobZ]

Hi @capital,

Aluminium is a soft metal, so there will definitely be some flex in them to account for the slight change in height. This is likely your best option.

If you wanted to widen the gap to use the timber stop, I would use a circular saw or track saw as opposed to a multitool. If you set up a guide or use a track saw, you would just cut along the gap to widen it.

If there was timber directly underneath the gap, then putting some Porta 30 x 5mm 2.4m Tasmanian Oak Rounded Edging Bead in the gap and cutting it off flush with the floorboards would work, but there would be little to no room for expansion and contraction or movement. If there is no timber beneath it, then it would need to be wedged in there tight, which wouldn't allow for any slight movement or expansion and contraction. This would likely cause it to crack over time. 

I think the aluminium t section is likely the best option.

Let me know what you think.

Jacob

[Noyade]

"as long as there is some flex in them"

Evening @capital 

Would a rubber "T" piece suffice?

https://www.google.com/search?client=firefox-b-d&q=Rubber+T-+molding

[Nailbag]

Hi @capital 

There are lots of options to choose from that both @JacobZ and @Noyade have suggested like these transition covers from one floor finish to another. If you fixed it with a flexible adhesive to say the pine floor side, it would allow any movement without any issues of the metal twisting from any long term movement.

Nailbag

[Dave-1]

Evening @capital 

I was thinking of the T piece of metal as well, and was half way to the next thought when I saw @Noyade's suggestion.

How about a bit of both? 

T piece but with a thin rubber strip on the low side of the floor (so only half with a thin rubber strip), it dosnt have to handle the whole height distance just enough so the T will sit flush with the transition between the dark and the light boards.

Dave