Latest Discussions : Tools & Workshop


05:34PM | 02/11/07
Member Since: 02/10/07
3 lifetime posts
I'm trying to put up some crown molding for the first time. I'm working on my first inside corner and I can't get the coped joint to line up nicely. I thought one of the reasons for using coped joints is that they fit together easily?

Anyways, I mitered the crown at 45 degrees using the "in place" method. I cut what appeared to be a perfect cope joint at the end of the crown. I went to assemble the joint and there is about a 1/8 inch gap at the very top of the joint where the top flats of the moldings come together. The rest of the joint fits nicely, but I can't figure out how to close this gap at the top. I tried tapping upwards on the first piece of crown to close the gap, but that didn't work. My first thought was that I wasn't getting an accurate cut with the "in place" method, so I went through this whole process again using the "flat" method with my compound miter saw, but I ended up with the same gap at the top of the cope joint.

I went back to the "in place" method and tried adjusting the miter angle to see if that would help. I found that the gap would close if I mitered at 41 degrees instead of 45 degrees before cutting the cope joint.

I have read a lot about how to cut cope joints, but there doesn't seem to be much written about how to adjust them to close gaps for a good fit.

I'm looking for advice on the best way to miter, cut and adjust cope joints in order to eliminate gaps at the top of the joint.

Also, are coped joints supposed to be caulked prior to painting?

I'm really trying hard to install this crown the right way by using coped joints for inside corners, but it's just not working. I thought coped joints are supposed to be forgiving for corners that aren't a true 90 degrees? I'm sure I'm doing something wrong and making this a lot harder than it needs to be.

Thanks for your help.


06:50PM | 02/12/07
Member Since: 12/27/02
543 lifetime posts
You don't say what material you are using, if it is paint grade or a situation where can't use a filler to the ceiling, or you just want to get the joints figured out.

Very few installations will require you to cope crown, I have been doing this for 30 years and with the new glues have found not coping the miter is best.. but that also is dependent on the material.

MDF for example is stable once climatized, so I always use a protractor for every corner and make a tight miter, the polyvinyl acetate (PVA) glues are like welding the joint.

But you do need to get the right spring angle as well as the corner angle, it sounds to me like you are cutting 52/38 crown with a 45/45 compound miter.. but it may be the ceiling plane is up in the corner.

Check the plane of the ceiling, and drop by my "how to install crown molding" site to get a bit more info, but basically if the molding rise and run aren't equal it's a 52/38 spring angle... but I've seen some new mouldings coming out of China that aren't designed the the American standards too. and have good articles on calculating the spring angle and installing on catherdal ceilings.. basically why I never covered it in depth on my site.

Alter Eagle Construction & Design | Construction & Design | | Decks, California outdoor living | | Molding and finishing | | Crown tutorial


07:24PM | 02/12/07
Member Since: 02/10/07
3 lifetime posts
Thanks for the reply. I'm really just looking for some advice on how to fit a coped joint to achieve a nice, tight joint with no gaps. My coped joints are good except for a gap at the top flat of the crown. Everything I've read says to use a round file or sandpaper to adjust the high points of the coped joint for a good fit, but that doesn't seem to be working for me. None of the videos I've seen show how to adjust coped joints for a nice fit.

I'm cutting 52/38 crown at a 45 degree miter angle using the "in-place" cutting method, and then I cut the coped joint with my coping saw. This is the method suggested by 95% of the tutorials that I've read. Some of my crown is paint grade pine and some is MDF.

Regarding the mitering of inside corners, I did check out your site and tutorial a few weeks ago. The problem is that your advice contradicts the advice of most other professionals who insist the only way to ensure a good, long-term fit on an inside corner is to use a coped joint. About 95% of what I've read says to use coped joints for inside corners, while only about 5% of what I've read says to miter inside corners.

It's somewhat frustrating for beginners like to me to read so much contradictory advice about installing crown. However, my perception is that the tried and true method is to cope inside corners and miter outside corners. I just need to get better at fitting the coped joints.


10:02PM | 02/17/07
Member Since: 12/27/02
543 lifetime posts
I hear you.

That's why I did my site to begin with. I own the outlet here that sells crown & architectural mouldings, and install it every week pretty well, be it on the custom mantels or the homes I work on doing custom cabinets & finishing work.

It was frustrating for me to see all of the web sites taking bits of information and piecing it together like they were professionals.

I'd tell you the years I've spent studying architecture & applying my trade, even went to Europe to get a closer look at the ancients works... but you'd probably think it was bull.

I'd like to get back to my site and add more and make it even more helpful but it's just too difficult to find the time for free to do it.

On coping.

Like I probably already said, it has it's applications but only on specific materials and circumstances, with the new glues & engineered materials it really isn't the right approach.

50 even 25 years ago it was, not now. Materials and building systems as a whole dictate a different approach.

Coping does have it's place.

If you want to discuss it and find out why you aren't successful use my crown moulding forum we'll go through it in depth.

Alter Eagle Construction & Design | Construction & Design | | Decks, California outdoor living | | Molding and finishing | | Crown tutorial


04:07AM | 02/19/07
Member Since: 04/10/03
116 lifetime posts
make sure that when you cope, you are taking enough material off of the back side. try over exagerating the amount of material you take off the back side just to see if it helps.


10:23AM | 02/19/07
Member Since: 12/27/02
543 lifetime posts
Yeah, good point whit.

Especially on those upslope ogees right, typically you back cut around 5 deg. but in some situations as whit. is so adeptly saying take a bit more so it won't hold the face out... sometimes it's just the simple stuff. :lol:

Alter Eagle Construction & Design | Construction & Design | | Decks, California outdoor living | | Molding and finishing | | Crown tutorial


10:45AM | 02/19/07
Member Since: 02/10/07
3 lifetime posts
I cut out more material on the back side and the joints are fitting a lot better now. Thanks for the advice.


09:51PM | 11/26/18
Make sure both profiles are the same as well, cutting more material helped but I spent past two hours trying to make two slightly different pieces of molding fit together

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