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Filling gaps between floorboards in bathroom

I've got old timber floorboards in my bathroom near the shower which have quite large gaps between them (~2mm). They end up with a lot of dust and dirt in them, and I'm concerned about water getting in and pooling - and I was considering filling the gaps - but found a lot of conflicting advice on Google about whether filling gaps is a good idea at all. There were also lots of conflicting suggestions about what to fill them with given there's likely to be future expansion/shrinkage. In addition to that, there wasn't really any advice specifically about wet areas.

Alternatively I wondered if I could just recoat the boards in that area with a layer of varnish to seal them a little? The original varnish near the shower base is pretty rough now (I've only had the house a short time but I'm guessing decades of moisture have played a part).

Thanks!

Chris

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MitchellMc

Hi Chris (@Chris_T),

It's great to see you've been receiving some excellent advice from our knowledgeable members.

You could use Cabot's CFP Water Based in this application. However, you'll find it gets a bit slippery when water sits on it, so I would suggest Intergrain 1L Slip Resistant Ultrafloor instead.

For the best results, I'd advise giving your floor a sand to remove imperfections.

Please let me know if you have any questions.

Mitchell

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Jason

Hi again @Chris_T,

Can you please tell us whether you can access under the house? It might be helpful for members to see some photos from the other side of this gap to see if water is getting through and if so, what damage it might have caused.

Once you've let us know I would be more than happy to tag some helpful members to share their thoughts on how they would tackle this job.

Thanks,

Jason

Chris_T

Thanks Jason

I went for a bit of a crawl and got the below pic - the orange arrows point to the board with the gaps (the lighter board in the earlier photo). Doesn't seem to be any signs of water damage or leakage. Also revealed that the boards here seem to be newer than the boards in the rest of the bathroom (you can see one of the older boards on the left in the image below are much darker and have old water stains).

IMG_6814 copy.jpg

Jason

Many thanks for the photo @Chris_T, I think that will be helpful to other members to see what you are working with. It's great that there's no signs of water damage.

Let me tag helpful and experienced members in @JDE, @Mathy and @tom_builds for their thoughts on next steps. @EricL will also be happy to assist as soon as possible.

Jason

JoeAzza

Hi @Christomk,

I have used Selleys No More Gaps to fill in gaps on baltic pine floors, however, my floors are painted not varnished like yours, Bunnings do sell a coloured version of No More Gaps, see below.

Selleys 380g Baltic No More Gaps Timber Floors Gap Filler - Bunnings Australia.html

Chris_T

Thanks @JoeAzza - to be honest there have been a few dodgy patches done over the years in this bathroom, so an absolute match probably wouldn't be a disaster. I'm more focussed on trying to give it as much water resistance as I can right now to give the floors a little longevity until an inevitable full bathroom reno!

Chris_T

As I'm currently not able to go in to a Bunnings store, does anyone know if these no-more gaps products have a colour reference in store? I was thinking of online ordering but I'm just going to be guessing the colour but if there's a reference in store I might wait until stores open again...?

TedBear

Hi @Chris_T , if you are planning to reseal the floor, you could 'almost' fill the gaps with gap filler, then sand the floor keeping the surface dust. (Empty the sander's dust bag first, so it only contains the dust from the boards.) This will provide a filler of the right colour which mixed with a small amount of clear lacquer can be wiped into the top of the (now shallow) cracks. Then reseal it all.

Chris_T

Thanks for the tip @TedBear - I had heard that approach mentioned in DIY videos but couldn't find any videos of someone actually doing it... But this bathroom is probably the best place to try it out - maybe I'll make my own video! Actually when I was under the house I found a few offcuts of the flooring timber, so I might even be able to sand some sawdust off those.

TedBear

That sounds great... making your own video of the process will give others the confidence to go ahead.

Also good news that you have some boards to convert into correct coloured filler.

I have used this technique when I made a kitchen bench-top out of floor boards a few decades ago and needed a continuous, smooth surface.

I just mixed the wood dust with a little water based wood glue to make a filler. It was strong enough since I was lacquering over it.

(That was before we all carried video cameras as phones, so I didn't video the process either, but the outcome was excellent.)

EricL

Hello @Chris_T

It's great that you've received excellent advice from @TedBear. His recommendation is perfect and is a great way to fill and colour match at the same time. If you think you will need a more substantial filler, I suggest using Timbermate 250g, Pine Wood Filler, this filler comes in many timber colours. I recommend getting one that is the closest match to the colour of your timber floor. Combined with TedBear's sawdust technique, you should get a near-perfect match filler. Please keep us updated. I'm sure our members would love to see a video of your timber gap-filling process.

If you need more advice or information, please let us know.

Eric

Chris_T

Thanks - @EricL - I do have some Timbermate from an earlier patch I did in the bathroom, so eager to try the sawdust trick out.

Also I've been reading about Cabots CFP Floor and wondering if that's an easier way to revarnish the area after I've filled the gaps (the no sanding version) - but just not sure because it's water-based whether it would be suitable for a wet area like this?

Cheers

Chris

MitchellMc

Hi Chris (@Chris_T),

It's great to see you've been receiving some excellent advice from our knowledgeable members.

You could use Cabot's CFP Water Based in this application. However, you'll find it gets a bit slippery when water sits on it, so I would suggest Intergrain 1L Slip Resistant Ultrafloor instead.

For the best results, I'd advise giving your floor a sand to remove imperfections.

Please let me know if you have any questions.

Mitchell

Chris_T

Thanks @MitchellMc - I'll go with the intergrain - can't hurt to improve the safety while improving the aesthetics!

Chris

Chris_T

Quick update on fillers - I tried a few options (See image below).

I used Selleys No More Gaps Timber floors. On the left I pressed in raw sawdust on top after applying, the middle is just plain No more gaps and on the right of that I added a little Feast Watson maple stain. The most surprising was the wood glue/sawdust mix. It dried really really dark, which was kind of unexpected. I'm going to leave for 24 hours and see if that changes, but I think the best result appears to be the no more gaps with stain (especially when you're not looking at it from 10cm away with lots of light as in the photo below!)

But wondering if anyone knows what I'm doing wrong with the wood glue/sawdust? It's 1:1 sawdust and Tarzans grip wood glue - maybe I should be using a different wood glue?

Just to see it in context without all the horrific macro detail.

MitchellMc

@Chris_T,

That No More Gaps with stain is looking fairly close to the coated floor colour. Bear in mind that with the raw sawdust, you are replicating the uncoated, natural timber colour, and it will need to be stained/coated to resemble the coated boards.

I'm really not sure what has gone wrong with your PVA/sawdust mix. It's much darker than what I would expect. You didn't add stain to it at all? Using that method, it should come out almost identical to the raw timber colour. I've got an example drying for you at the moment to illustrate. All PVA glues are white and dry to semi-translucent. I can't imagine where this brown colour came from.

Mitchell

Chris_T

Did another test last night - same issue - maybe the ratios are wrong? I'm doing about 1:1, maybe it should be more 2:1 (more sawdust?)

MitchellMc

Hi @Chris_T,

Thanks for the follow-up. Try hitting that dried sample with some sandpaper. I believe you'll find once done, it will be much lighter. My sample has also become much darker overnight, but after sanding, it has revealed a lighter shade. Your sample in the floorboards is a bit too deep to sand, but try it on the sample you've just posted. Use something similar to 120-grit.

Mitchell

Chris_T

Thanks @MitchellMc - sanding does help!

Cheers

Chris

MitchellMc

That's great to hear, @Chris_T.

I believe the PVA is creating a coating that needs to be opened up to see the true colour. Keep us update on your progression.

Mitchell

Chris_T

Ok - so I've filled the gaps and sanded back. When I did the sticky-tape test, the intergrain did come off, so I'll followed directions and sanded back to bare wood. However, there are a few indentations in the wood - either patterns in the wood or indentations from dropped items - which are still a little "glossy". I don't want to sand back too much - would it be safe to assume these smalll areas won't be an issue and I can just go over them, or is it worth trying to use some kind of stripper to get it all off?

IMG_7124.2021-09-11 14_35_46.gif

MitchellMc

Hi @Chris_T,

It's one of those things where, in a perfect world, you'd want none of the previous coating left. Will you see any adverse effects if you coat over? Probably not, but it's hard to give a definitive answer. I believe even if you were to use a stripper, you'd find it difficult to get the remnants out of the crevices. You now have plenty of surface area the new coating will bind to, which should offset any tiny areas left to which it won't adhere.

If this were my floor, I'd take the chance and coat over. The amount of work it will take to get an ever depreciating amount of coating off, I feel, outweighs the benefit.

Let me mention @TedBear to get his thoughts.

Mitchell

Chris_T

Yeah that was my vibe too, but I've never used a stripper before so wasn't sure how successful it was likely to be. I'll give it a little more light sanding to make sure I've got off what I can, and get on to varnishing!

Thanks
Chris

TedBear

I agree with not trying to achieve perfection. A lived in home (& its floor) needs to have character.

Chris_T

Some photos from the process - I haven't revarnished the floor yet, but everything else is done and it's looking pretty good!

IMG_7056 copy.jpg

IMG_7093 copy.jpg

Pre-stain

IMG_7069 copy.jpg

Post stain

IMG_7202 copy.jpg

MitchellMc

Nice work @Chris_T! That looks very uniform after the stain. I'm waiting with anticipation to see the final results. You've certainly put in the effort.

Keep us updated.

Mitchell

Chris_T

It's been a while, but final got around to finishing the bathroom floor. Looking good, but the improvement is probably not so visible from the photos. This was mostly a preventative measure to try and seal the gaps and protect the boards from water drops from the shower, which it does much better now.

Here's some photos. Boards also match the old boards pretty well!

Thanks for all the help!

IMG_7775 copya.jpg IMG_7777 2 copya.jpg IMG_7789 copya.jpg

MitchellMc

Great work @Chris_T! I'm pleased to see that's worked out for you. As you mentioned, even though there is also a visual improvement, the real benefit will be in preventing rot within the boards.

We can't wait to assist with your next project. Reach out any time you need assistance.

Mitchell

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