Finishing MDF Baseboard

[Doug Kock]

I am looking for advice on what to use on my baseboards to fill gaps. We had all of the baseboards (mdf) in our house professionally installed but my wife didn't like the way the installer was going to "stair-step" the baseboards down a short flight of steps - so she told him to let it go and I would finish it. Lol...

Anyway, as you can see in the pictures, I've completed it the way she wanted it to look but, for various reasons, I had to fill spaces with additional mdf pieces (cut from extra baseboard so the thickness matched). The problem is that not only do I need to fill some gaps, but due to the sheetrock beneath, the points where the edges meet are not all flush (even though the mdf is cut from the same product).

I am hoping that someone here can offer advice on what material I can use, not just to fill the gaps, but also spread a skim coat that will allow me to sand the whole panel smooth (this rules out caulk). I tested using basic wall mud on a sample joint and it seemed to work but I''m not sure about its durability or that it won't crack over time. While I am doubtful, I am hoping that whatever material I use will survive any movement in the mdf (swelling, etc.). Once the gaps are filled and the baseboard sanded smooth, it will be painted to match the rest of the baseboards. Can anyone here point me in the right direction?

Thanks for any help,

Doug20180210_165246.jpg20180210_165240.jpg20180317_091924.jpg

[Bill McNiel]

Bondo will probably do fine.

[Michael Pyron]

your installer wasn't worth his salt if he was unable to put a skirt board in and do the look your wife desired (that's certainly a big part of any tradesman's job...make the customer happy and do as they desire (in general...there is always a budget and perhaps a boss's directives to consider))

that being said, unless you glued all joints then any attempt at filling is bound for failure due to material moving.

Bondo is used all the time in the field as prep for paint grade work. I use it myself when being required to hand the painter a fully complete, ready to paint project. I've even been required to prime anything I do that leaves exposed material.

[Doug Kock]

Thanks for the responses. I see now that Bondo actually has a wood filler product with the same 2 part process. Would you recommend this or the standard auto body version?

[Michael Pyron]

I, and the majority of painters I deal with, use the auto body version...I prefer the one with red hardener as it's far easier to see by resultant color what the mix is...too much and it hardens too quick, too little and it doesn't harden.

[Doug Kock]

Thanks for your help

[Bill McNiel]

I, and the majority of painters I deal with, use the auto body version...I prefer the one with red hardener as it's far easier to see by resultant color what the mix is...too much and it hardens too quick, too little and it doesn't harden.

I am with Michael on this. I believe the auto body stuff is a little less costly as well.