We have just had an extension built but there is now a large gap between where the concrete step from the external door used to be and the wood floor that has been built next to it. We are just about to have vinyl flooring laid down and I’m looking for the best solution to fill the gap.
I’m thinking a thin sheet of 1.00mm metal laid over it is my best bet. Struggling a little and any help would be much appreciated!
You don't bridge something like this, especially with thin metal. That would leave you with an ever-sagging trough as traffic stretches it out.
You also don't use caulk, foam, or any other soft material as sheet vinyl flooring requires a hard, flat, stable substrate or you'll see the depression telegraph through over time.
I would probably use a vinyl concrete patch, though it's important that it be a product designed for gaps that wide. Some materials shrink too much.
You could also use masonry mortar and then skim with a finish coat of leveler designed for vinyl floors.
If I understand the picture right, all you need is to fill this up with either foam and/or caulk, since you will presumably have a threshold installed under the door. Whatever you decide to use (foam or caulk), insert a backer rod first, so that the material does not fall down.
It's now an expansion gap and should never be filled in with anything solid as it will crack. Vinyl over it, put in a false seam glued to one side only, so the two slabs can move independently. The crack will always be there...not a problem. You hide it under a flat threshold or transition piece.
I would suggest using a construction sealant, specifically Sika brand. It’s super stick yet will remain flexible forever. I would not suggest any of the concrete patch products because their self leveling makes them run away on anything vertical. Don’t substitute. You can foam back it if you need to
