How to repair damaged Jarrah floorboards?

[Rys]

I've noticed a few weak wooden blocks that seem like they might break if any pressure is applied. The damage shown in the first picture was caused by the couch legs pressing into one of the blocks. I’d really like to fix that specific section. Personally, I feel that replacing just that particular wooden block might be the best option—if that’s even feasible. I have zero experience with this kind of repair, but I’m highly determined to learn and get it done right.

[MitchellMc]

Welcome to the Bunnings Workshop community @Rys. It's sensational to have you join us, and many thanks for your question about repairing floorboards.

 

When it comes to repairing your floorboards, there are really two main approaches. The first is replacing the timber board entirely, which is generally the most robust and long-lasting solution, especially if the board is weak or partially broken. Since you mentioned the boards feel unsupported, the subfloor may also need reinforcement, which could mean adding new timber battens or blocking under the damaged section before installing a replacement board. If you can source a board of the same size and species, and it isn’t tongue-and-groove, a D.I.Y. replacement is quite feasible. You would need to remove the damaged piece, reinforce the subfloor if necessary, and install the new board securely. However, if the boards are tongue-and-groove, replacement becomes trickier, as the new board has to fit precisely, and sometimes adjacent boards need to be loosened or partially removed to insert the replacement. In this case, a professional carpenter or flooring specialist is often the best option to ensure a seamless fit.

The second approach is filling the missing piece with wood filler, which is something you could realistically attempt yourself. The challenge here is that the area of missing timber is quite large, making it difficult to achieve a seamless finish that matches the surrounding wood. If you still have the missing piece, it might be possible to glue it back in with some filler for support. Without the original piece, filling will result in a noticeable patch, and matching the colour and grain of Jarrah can be tricky. While filling can work for minor damage, it’s less durable and less aesthetically perfect than replacing the board entirely.

In either case, addressing the support beneath the floorboards is important. Even the best repair won’t last if the subfloor continues to allow movement or has weak spots. For a long-lasting and visually seamless result, replacing the board with proper subfloor reinforcement is ideal, but if you’re keen to try a D.I.Y. fix and accept some visible patching, filling with wood filler is a possible alternative.

Please let me know if you have any questions.

Mitchell
 

[Rys]

Thanks Mitchell, 

I don’t feel like there’s a subfloor—I’m only saying that because when I walk, I hear a lot of foot noise. Or am I mistaken? Also these are tongue-and-groove boards, so I may need to seek a professional for this job.

[MitchellMc]

Sorry @Rys. When I say subfloor, I'm referencing what's below the board, specifically the joists and bearers. You likely need to add additional joists or blocks under those areas if they are not well supported.

With tongue and groove, I'd recommend seeking professional assistance.

Mitchell

[Rys]

I initially thought by subfloor you meant was what’s highlighted in the image below:

 

However it’s the joists block underneath and structure somewhat similar to the below image.

I’ve also confirmed this with a stud finder, as the density only increases in the areas where the nails have been placed. 

[MitchellMc]

If a timber board is flexing underfoot, it's likely that the joists are not supporting it well, and additional support should be added @Rys. This could be in the form of a block of timber between the joists that runs underneath the flexing board.

Mitchell

[Rys]

What type of timber should I use for the support blocks between the joists, and how thick should these blocks ideally be? Also, what other materials and tools would I need to get started on this project?

[MitchellMc]

The size of the blocks really comes down to the area that needs supporting, @Rys. You'll need someone under the house and someone inside. The person inside can step on the areas, causing them to flex. Once the areas have been identified, you can install the blocks of timber beneath them. Something like 70 x 45mm timber would be suitable. You'll need a drill driver and screws in order to install the blocks.

For the floorboards, will you be hiring a professional to replace them? If so, I'd recommend you have them do that first, as they'd likely be able to install some additional support blocks if needed. You might find that once the damaged boards are replaced and reattached to the joist, the flexing goes away.

Mitchell

[Rys]

Got it, thanks Mitchell for all the advice and recommendations.