How to patch Masonite siding prior to painting?

Our house was built in the 60s with Masonite (may not actually be Masonite, but you get the idea) siding. In the past few years, some of the siding has been damaged due to old cables being removed and my dogs gnawing on a few edges. The siding itself is still in good condition, but some small areas/patches have the interior of the siding exposed. Of course, it has a rough texture and needs to be sealed against moisture.

What’s the best way to do this? I could apply a primer or sealer, but that won’t help the texture. I guess I could use joint compound, but I’m not sure it would last in the exterior environment. Would a pro painter just say, “I’ll take care of that for you for $X?”

Is there an experienced person out there who has dealt with this issue? The exterior is going to get painted soon, but I don’t want them painting a surface that looks like the inside of a biscuit.

You can still buy similar siding and patch the bad areas on your house.
Lowes and Home Depot stock several patterns. You should find something that will match.

This is just one example. They offer several styles of siding.|G|Base|D22|22-53_VINYL+SIDING|Generic|PLA|71700000033888451|58700003921204974|92700031718658394&gclid=CjwKCAjwtvnbBRA5EiwAcRvnps5q2XxJvaIiZHAVMDMGg4BNoZPNUocClAkaohp8pFih22vNoFYSxhoC_RsQAvD_BwE&gclsrc=aw.ds&dclid=CM2H4Jqrg90CFYZ9Ygodlu4A3A

My house was built in the 50’s. The original #105 yellow pine siding is still available. I built an addition and it matches perfectly with my old house.

My first house had Masonite siding. I repaired a few areas with ordinary auto body filler - Bondo. It worked quite well.


The best way to deal with this is buy new pieces of Masonite and replace the broken pieces … if this isn’t available, find an out of the way part of your house and remove the Masonite, put up some new siding and use the pieces to replace the broken ones … lacking this just use Bondo or some other plaster to fill in the broken spots … just make sure you have a good bond and that water will shed properly …

You’re painting and paint covers a multitude of sins …

Thanks for the suggestion about replacing it, but this is definitely what I want to avoid. There’s nothing at all wrong with it…no warping or bubbling. It’s just that some cable got removed and, since it had been painted in place, it peeled off some of the paint and finish in small patches (3"-5"). I’m looking for a $20 repair, and I would have to have at least eight pieces of siding replaced to get all the problem areas.

I may give Bondo a shot at it. Hadn’t thought of that.

I’m also thinking that there are some exterior vinyl spackles I might try. I can use a broad putty knife and then sand it a bit. The surface is rough and fibrous, so it ought to adhere pretty well.

Just went thru this with another round of repairs and then a complete paint job.

The current replacement material is HardiePlank ™. Unfortunately for me they don’t make it as wide as the existing siding. So for this job the painters really scrounged around for some of the right width and style (beaded edge). It came out looking pretty good.*

There are several ways Masonite gets damaged. The bottom edges can peel off. I’ve glued them back down and if that’s not possible I caulked them. I made a tool the shape of profile and would smooth it out like a plasterer.

Nail holes and such can be filled with standard painters putty. Be sure to caulk all the edges where the boards meet molding. Protecting edges is the key to making Masonite last.

For bigger issues, an epoxy type filler should be best. I find Bondo to be too quick setting, hard to smooth out, and hard to sand flush. There are two-part things that are more like wood filler that I find easier. OTOH, the squirrels like it a bit too much if they can get to it. :frowning:

  • They bought too much so now I have several long pieces that I have to get rid of. Any takers in the Atlanta area?

Thanks, ftq. Helpful.

As I said, there’s absolutely no need for me to replace any of the siding. It’s perfectly sound except for the few pieces of finish that came off. The whole job would probably use less than half a cup of filler/spackle.

I wish I had something around the house that would work on the beaded edge, since I have a couple spots that could use filler/spackle and just need something of an appropriate radius to smooth it.

For smoothing off shapes, trim up a piece of plastic from a gallon milk container or similar using shears, scissors, or a knife. I did that several years ago for repair on some siding (I used bondo - great) and got a good match with the existing grooves/beads. Passed the 10 foot test anyway.:slight_smile: