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How to install transition strip to cover gap between floors?

aranawar

We have removed the old carpet from the floor (where the cardboard is). I would like to cover the gap between the floors with a transition strip, but the issue is that the gap is hollow i.e. there isn't anything under it to install and fix a transition strip on. The gap is around 10 mm in width, but it also narrows in some part (see the image). Is there any way to cover this gap (other than a sealant or a gap filler), so that I can screw a transition trip on to? or a better way of covering it? Thanks.

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EricL

Hello @aranawar

Thank you for sharing your question about your flooring. One possible way to fill the gap is to make a timber filling strip and use adhesive to anchor it to the floor. However, for the smaller sections, I can only suggest using timber filler in the same shade. Any excess timber will need to be sanded or planed off.

The second option that I would suggest is to remove the horizontal timber piece and replacing it with a bigger one so that it gives a nice uniform look. The small horizontal pieces will need to be removes and the floor will need to be trimmed in order to get a uniform space for the replacement piece. I've placed a rendered sample image below using AI to give you an idea of what it would look like when that section is tidied up with a uniform replacement piece.

My best advice would be to try and identify the type of timber floor you have and see if you can source a small piece to patch your flooring.

Let me call on our experienced members @Nailbag, @Dave-1, @Noyade, @TedBear, @JoeAzza and @DIY4Knuckleheds for their recommendations.

If you need further assistance, please let us know

Eric

ChatGPT Image Sep 23, 2026, 09_15_12 PM.png

Nailbag

Hi @aranawar

I would go with a timber look trim from the flooring department with a short 90deg return that would locate into the gap.

Alternatively use a flat timber moulding which you could stain to match.

Use a Sika adhesive to fix it into place for a neat finish over screws or brads. This is how I’ve covered similar gaps in the past.

Nailnag

TedBear

Hi @aranawar. You said that it is hollow under the gap, so I am wondering what is holding up the timber strip that is there at present…?

If it is just jammed in place, I would remove that strip and the metal strip, then use a router to straighten the uneven gap edges before your start so that you only have one rectangular strip to fill. If possible make the rectangular hole the width of one or two standard timber strips, so that you don't need to cut one down to width & risk having uneven edges.

Then glue some timber strips (one at each end and one or two in the middle} across the underside of the gap, clamping until the glue sets. You could strengthen those supports by inserting thin nails into the end of the support strips before gluing in place. Once set, use the clamps (with protector pieces on top to protect the floor from marks) to force the nails up into the bottom of the floor boards. (If they won't go all the way, bend the heads over with a hammer. They'll be out of sight and will still add support.)

You will then have supports to pin and glue your timber insert to.

Dave-1

Good Morning @aranawar

Looking at your photo of the door sill itself, it appears to be nailed down, "crossing fingers" I would be tempted to see if I can lift it and replace it with a wider one that covers the gap. You may need to trim some of those little add on's as well (or replace the two with one of the same type of timber as the door sill itself. I wouldnt make a special fitted door sill that jinks to cover that spot as I think it would bring more focus on it.

The metal strip, is it covering a join? Or a drop in height?

Dave

aranawar

Thank you @EricL, @Nailbag, @TedBear, and @Dave-1 for replies and suggestions. Appreciate it!

@TedBear - The timber strip is base of the door frame. The gap you see is caused by an extension or extra room that previous owner added to the property. This wasn't part of the original build/plan.

@Dave-1 - The metal strip was there as a transition strip. The other side used to have carpet (hence it was covering all the gaps, but we have removed it now which is exposing these gaps). It's an old house so I assume the sill would have been nailed into the jambs. I have attached some more images.

Do you reckon an easy fix would be to use a timber filler/molding (stain to match the timber colour) and gap filler as suggested by @EricL and @Nailbag? I am not sure if replacing the sill with the wider one (is possible?) would help aesthetically and cost-wise given there's a gap extending to the wall too (as per the image)

Dave-1

Good morning @aranawar

Thank you for the extra pics :) Makes it easier to get a picture. (And just realised the pun lol)

It really comes down to what level of effort you want to go to and what type of finish that is acceptable.
If the trim around the door was removed then the sill could be lifted (presumption as you wont know until you get to that part but building backwards thats where I would end up)
Inserting a piece of trim maybe be an easier solution.
removing the carpet edge and replacing it with either a diagonal timber trim or a smaller rectangular one to blend better.
I had this thought earlier but wasn't really sold on it as I like timber floors :) How about a flat metal plate that covers from the edge of the door sill across and over the floor gap plus the extra pieces? You could coutersink the holes to get a low as possible threshold. Metal Mate 0.5 x 300 x 900mm Plain Aluminium Sheet It dosnt have to be aluminium, I was just using it as an example. If you know of a metal fabricator in your light industrial area they may even be able to bend stainless plate to cover the transition part.

Dave

MitchellMc

I think @EricL's approach of replacing the existing horizontal section with a larger, more uniform piece is worth considering here @aranawar.

Although this could certainly be tackled as a DIY project, I think the quality of the finish is particularly important with a timber floor like this. I'd be inclined to enlist the services of a flooring professional to cut out the existing uneven section, trim the ends of the floorboards neatly and squarely, and then install a nice timber transition piece perpendicular to the boards.

It would involve a little more work initially, but I think you'd end up with a much cleaner result that looks intentional rather than trying to disguise the various gaps with filler and moulding.

Mitchell

aranawar

Thanks, @Dave-1 and @MitchellMc. These options will certainly help me to make a decision. Appreciate your help on this! :-)

Nailbag

Hi @aranawar

Looking at those last set of photos provides a much clearer scenario and quality of the condition and finish of the floorboards is high. I would be very much inclined to go down the lines of what @MitchellMc has recommended. It's a project I have had to do a few times and isn't an easy one by any stretch in as far as being able to make the cleanest straight cuts to form the opening. It's definitely an advanced DIY job or for a professional to tackle. But the result in my mind will provide the closest to a seamless transition between the two floor spaces.

Nailbag