Short Run Patch and Match Pieces for Custom Crown Moulding

Suggestions for ways to match the look of old existing crown in a few small areas. August 15, 2011

I'm doing some work for a customer that has 5-1/5" crown (approx 70 lin. ft.) already installed/painted. I need only 2-3 ft to splice into areas where previously there were structures that interrupted a run; a couple of 6" voids, a 10" void, etc. I’ve been to all of my suppliers and nothing comes close.

Any ideas how to make something that would work? I've seen how plaster crown is recreated with an onsite profile made of the existing moulding and then pulled along with plaster. Can't mix plaster with wood, but would some other material work - bondo, or other? Any ides would be welcome. I really don't have the option of replacing crown in the entire room ($400-500) or having knives ground for 3' of crown that probably would be close to the same price.

Forum Responses
(Architectural Woodworking Forum)
From contributor B:
Bondo will work. Just be sure to use marine bondo, that's the green or blue one. The hardest part will be making to pull knife. I've used 1/4" plexi with great success. If you have the wire contour tool just put it to the existing crown to get your pattern. Then detail it with a file and sandpaper. I always try to put an angle on the draw edge.

Build up the area with wood that has some crossed kerfs in it for the bondo to grab on to and it will give you a bit more strength. Try to get the wood close to the pattern you need. Do a buildup of the bondo - usually it takes three times. The first pass does the main profile, the second fills in the gaps, and the third is the finishing pass. Feel free to mix it a little bit hot for the first time. Sponge sanders work nice for the final detailing.

From contributor M:
If nothing comes close at the retail yards you'll have to suck it up and get it made custom. Some millwork shops have lots of profiles, so maybe someone in your area has a close match that would work. As far as a work around, we always say "you’re tripping over dollars looking for dimes".

From contributor Y:

I don't know what the profile is, but if it's not too complicated, you might try putting in a 6" piece of 6/4 or 8/4 white pine and going at it with a block plane, chisel, gouge, and sandpaper. Or you might scribe the profile on the end of a piece of wood and bandsaw it out. Be sure to screw it to a larger block or hold it with clamps so you don't lose a hand. You’d be surprised at how easily some profiles can be made. I once bandsawed out a three inch piece of oak mold for man who had been all over the country trying to get someone to run a short piece. I did it in about five minutes and it made him very happy. The bondo might be just as easy though.

From contributor C:
Anyone with a CNC could make this moulding if you provided them with a profile. A thin slice can be scanned into a program like Aspire and run on a Shopbot. We do this sort of thing frequently, and it is really not that expensive. Look for someone in your area.

From the original questioner:
Thanks to all for the ideas. After putting up what's left of the pieces, its two 4" pieces so I think the bondo route is the way to go.

From contributor M:
You guys have got to be kidding me - CNC, plaster, bondo, and carving blocks? There would have to be a really good reason other than the money to not simply remove the old crown and replace it with new. I ran the numbers and for 70lf of crown in poplar 5-1/5" with a new knife and it would be $480.00 in my shop. As far as install, a good carpenter would have that old crown down and the new in before your first layer of bondo even dried or you fitted and secured your first carving block. Add in the hack factor and the appearance of a patch job, I just can't see the other methods being cost effective. Am I missing something?

From contributor Y:
Contributor M you are right, but if I understood his question it was how to do it without making new mold and replacing the old. I would charge $50.00/inch for knives, 6" knives = $300.00, $50.00 set-up, and about $2.00/ft for the mold. This is $490.00. I'm not sure what carpenter labor and painting would be, probably another $300.00 or $400.00. He wants to know if there's a less expensive way. I agree with you about just replacing it, but if I were doing that, I would try to use a stock mold rather than custom running it since there are so many profiles available now.

From contributor U:
Thanks to Contributor M for making sense of this thread. I have never heard of so many round-about solutions to a simple problem. Replace will take less than a day and be cost effective. Even to make a matching knife and running 12-16 l/f may sound expensive but is very cost effective.

From contributor H:
How about posting a tracing of the moulding profile? Many shops have hundreds of knives on the shelf and somewhere there could be a reasonable match.

From contributor B:
Since you only need the two 4" pieces , simply bandsaw them a little wide and cut them to fit after final scraping and sanding. It may take you an hour or so but it will be perfect to the eye.

From contributor V:
I make all kinds of molding in short runs, mostly to match the molding on homes in the area which were made 100 years ago or so. I would like to see a profile of the piece and I can tell you more. Other than this I agree with the person who said to use a bandsaw. For very small runs this is the most efficient way to produce a custom shape. Remember that you don't have to run the wood all the way into the wood you can just cut to a profile line. If the piece is too small glue it to something else or use a screw if it is to be painted. Don't think so hard and the answer will come to you.

From contributor F:
The original poster said he needs 3-4 ft, which puts bandsaw solution out of the question. A bondo solution would work (moulds were made like this for centuries) but to get good quality with sharp detail and no ripples you will need a lot of skill and patience which is also expensive. My bet would be to run it on a flat bed CNC router. Machining should take two hours max. No custom tooling and you have a perfect match for any crown, in any species.