Futher to my other post about the external old termite damage, I have discovered some historical termite damage in my floorboards that have made some small areas "spongy" - obviously there's some cavities in the wood. There is still structural integrity in the boards overall, so I'd rather not go down the path of replacing the boards just yet - I'd just like to fill the spongy areas so they don't continue to deteriorate. My initial thought was to fill them with builders bog and do a layer of timber filler or mixed sawdust glue to make them less noticeable. Just wondering if there's a better approach or if I'm way off?
My other (insane) idea was to cut out a chunk and replace with similar board material (I have left off boards from a renovation). I've seen people do that sort of thing on YouTube, but feels kind of intense!
And yes, if anyone is following my other posts, I haven't yet done the bathroom boards (work just got crazy) but I'm back on the DIY renos now, so that will be updated soon!
There are likely a few methods that could be employed to fill this area @Chris_T.
I'm in the corner of replacing the section of the board if you have a matching length. That's a permanent solution and likely something a carpenter would advise. You have some great experience with fillers now, so I'm unsure what more I could add to that. To assist any filling you do, you might like to use some Earl's 250ml Wood Hardener to bind and solidify the surrounding timber. It can also be put in a syringe and injected into the timber. However, anything that can easily be removed by digging it out with a screwdriver should be taken out.
I'd suggest you start by doing a bit of exploratory work. Take a flathead screwdriver and start digging in the area. If everything around the hole is solid, you might like to fill it, but if you can dig out a much larger hole, I would personally replace the board section.
Please let me know if you have any questions.
Thanks @MitchellMc - I was afraid you'd suggest the board replacement! I think one of the reasons I'm nervous about doing that at the moment is that I'd like to give the boards a few years to reveal the actual extent of the damage to see if other nearby boards start to soften, and then do a replacement en masse, rather than replace a couple more next year, then a few the year after that. Pessimistic, I know, but I haven't been in the house long enough to really see what the seasons do to the boards.
Luckily they're all in areas that have very low foot traffic and not obvious to the main house, so I can afford to experiment a bit with them. Maybe I'll give the filler a go and if its not a great result, I'll bite the bullet and replace the boards. I'm more confident with revarnishing now after my bathroom investigations, so I'm less concerned about not being able to match the new boards with the existing ones.
Thanks again for your advice, gives me a little more confidence I'm doing the right thing!
I'll document my journey, and report back - but I should probably get that bathroom done first!
If there is a plan in the works to possibly replace more boards, then I suggest giving the filler a go @Chris_T. If that doesn't work, you can always replace the board section. I can't see any harm in attempting to fill the area first. Since there is going to be low foot traffic, filling is less of a concern for me now.