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  1. #11
    Join Date
    Jun 2011
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    208

    Default Re: Coping Crown Moulding

    I THINK I KNOW!

    Lemme cover my A$$ by saying right up front that I've never installed crown molding. But, I'm intimately intimate with plaster walls and I've coped more than my fair share of miters.

    Loveswood said: "My house is rather old..."

    If that's the case, she has PLASTER WALLS, and that means she has EXPANDED METAL corner beads where walls meet ceilings.


    (only an inside corner bead instead of an outside corner bead)

    As anyone who's ever done any renovations on plaster walled buildings knows, the plasterers would have put the plaster on thicker at the corners to cover the nails and expanded metal corner bead. I've seen plaster in corners that was a full 1 1/2 inch thick (instead of 3/4 inch)!

    So, maybe the root of the problem is that Loveswood's wall/ceiling corner isn't a 90 degree angle like you're more likely to get between a wall and a floor. If she's got something LARGER than a 90 degree angle between her walls and ceiling, then fitting crown molding into inside corners where walls meet is gonna be darn near next to impossible to get right.

    Same for outside corners where walls meet.

    Loveswood: Do this:
    Check the wall/ceiling corner angle with a carpenter's square.
    Also, if you have some crown molding's you've already cut, try fitting them in at a 90 degree corner, between fridge and floor, say. If your wall/ceiling angle is funky, but your crown molding fits well when the corners are all close to 90 degree angles, then that's what the problem is... you're trying to fit crown molding that's meant for 90 degree angles into corners that can be considerably larger than 90 degrees.
    Last edited by Nestor; 07-24-2011 at 05:12 PM.

  2. #12
    Join Date
    Jan 2010
    Location
    Northern Virginia
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    1,132

    Default Re: Coping Crown Moulding

    Real plastered corners are usually squarer than the modern drywall equivalents, expanded metal reinforcements notwithstanding. Plasterers will float or rod their browncoat dead flat, because the white coat's easy application demands it. Impossible to drive a finish nail into, yes, but out of square, no.
    Drywall finishers will typically only feather a wall/wall or wall/ceiling corner out the width of a 6" knife. So every drywall inside corner comes with an out-of-square guarantee. Anyone who runs baseboard and crown will know of which I speak.
    Casey
    Remove not the ancient landmark, which your fathers have set.

  3. #13
    Join Date
    Mar 2008
    Location
    nova scotia, canada
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    1,522

    Default Re: Coping Crown Moulding

    i hear yah on that one casey...
    your right about the plaster walls being square... technically they should be more square. but it also comes down to the framing job and how much the old house has moved

    hense why whenever i go into a old place i always expect nothing to be square, every corner is checked for teh angle first and i always test the peice first before i cut to the final length
    fire up the saw and make some dust

  4. #14
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,775

    Default Re: Coping Crown Moulding

    It shouldn't matter if the corner is 90 degrees or not when coping, which is what she said she did. Copping will work when the wall is out of square by several degrees.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  5. #15
    Join Date
    Jun 2011
    Posts
    208

    Default Re: Coping Crown Moulding

    Loveswood:

    You have nothing to lose and much to gain by simply checking your wall/ceiling corner to see if it's less than, equal to or greater than 90 degrees.

    In my building, the plasterers nailed up expanded metal on all inside and outside corners. This expanded metal is a good 1/8 inch thick, much thicker than the paper tape used today. As a result, the plasterers would lay a thicker brown coat of base plaster as they approached inside corners so as to cover this expanded metal corner bead. But, since this kind of work wasn't done with screeds, but freehand, sometimes they applied way more plaster than was necessary to cover the expanded metal corner bead. But, since no one was going to be installing crown moldings, as long as it looked OK, it was primed and painted.

    I am reminded of that every time I clean a wall or ceiling with my Taski Vertica cleaning system. This tool is essentially a squeegee 16 inches wide which you can connect to a wet/dry vaccuum cleaner. EVERY TIME I run that squeegee along the wall/ceiling corner, I leave behind a puddle of water on the ceiling about in the middle of the squeegee. I can see that water because my windows come almost up to the ceilings in my building, and light reflects off water differently than it does of damp paint. To prevent those puddles, I have to run the squeegee perpendicular to the wall/ceiling corner so the rubber follows the contour of the plaster.

    Regardless of what was said in the previous two posts, the plaster in my building gets thicker toward the inside corners where walls meet ceilings and where walls meet walls. If your house is the same, then the root cause of the problems your experiencing is that you're not installing your crown moldings into 90 degree corners meeting at 90 degrees. You've got something like 95 degree corners meeting at 95 degrees, and that's gonna leave 5 degree tapering gaps all over the place.

    And, as a result, it's no wonder you're having problems getting your coped miters to work, whereas the exact same procedure yields nice fitting baseboard moldings at the base of your walls (where the wall meets the floor at an angle very much closer to 90 degrees).


    JLMcDaniel: You said:
    It shouldn't matter if the corner is 90 degrees or not when coping, which is what she said she did. Copping will work when the wall is out of square by several degrees.
    What you're saying is correct if the walls meet the ceiling at 90 degrees, but the walls don't meet each other at 90 degrees. That happens all the time when installing baseboard moldings. In fact, most of the reason we cope miters instead of just cutting the moldings to 45 degrees is to accomodate the fact that walls can meet walls at something other than 90 degrees. However, coping miters won't work if the walls don't meet the FLOOR at 90 degrees (which is the situation Loveswood is dealing with at her wall/ceiling).

    Imagine you're installing baseboards in a house. Imagine that instead of the wall being vertical, imagine it sloped away from you at 95 degrees. Now, imagine you have in inside corner where two such sloping walls met; both sloping away from you. If you butt one baseboard into that inside corner, miter and cope the other baseboard, you'll discover it won't fit cuz both baseboards are leaning backward at 95 degrees. There's a gap at the top that you wouldn't have if both walls were vertical. And, that's the problem Loveswood is trying to overcome at her wall/ceiling corners.

    I'm willing to bet Canadian dollars to American donuts that Loveswood knows exactly how to cope a miter. I'm also willing to make that same bet that NONE of us could do any better a job than she's doing installing crown molding because coping miters only works where the walls meet floors or walls meet ceilings at 90 degrees (or close to). As the reality of the situation gets further and further from that ideal situation (as it does in my building), then coping miters is going to give progessively worse and worse results. And, that's exactly what you run up against with plaster walls and plaster ceilings where the plastering crew put on a greater base coat plaster thickness at inside corners to bury expanded metal corner bead. The surface of the wall doesn't meet the surface of the ceiling at 90 degrees anymore, thereby creating exactly the same problem you'd get if the walls weren't vertical.

    PS:
    It occurs to me that homeowners having trouble installing crown molding is a COMMON question in these forums. I'm wondering if in most, if not all of those cases, it was homeowners trying to install crown molding in older homes with plaster walls and ceilings.
    Last edited by Nestor; 07-25-2011 at 02:26 AM.

  6. #16
    Join Date
    Sep 2009
    Location
    florida
    Posts
    598

    Default Re: Coping Crown Moulding

    Quote Originally Posted by jkirk View Post
    you may also have 52 degree crown...

    there are two different types of crown, there is 45 degree and 52 degree

    52 degree sits more on the wall and less t the ceiling. where as 45 deg has the same lie on both wall and ceiling. because of this the angle of the cut ends up being different
    JK the degree of the crown makes no difference when cutting the crown standing up in the miter saw. It will if your laying the crown down flat on the saw table....then you need to use compound degree settings.

    The 2 different crowns are 52/38 & 45/45, if you add the to numbers together on both different crowns they will always equal 90 deg.
    Gizmo

    Cut it 3 times & it's still to short.
    Inventor of the Miter Master Plus.

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  7. #17
    Join Date
    Jun 2007
    Location
    Coventry, RI
    Posts
    340

    Default Re: Coping Crown Moulding

    Installing crown molding as we all know is probably one of if not the most difficult finish carpentry tasks. Your dealing with molding that doesn't sit flat on the wall, working overhead, out of square walls and ceilings, etc.

    As for doing molding whether it be crown, baseboard, or chair rail, on walls that are out of plumb or a floor or ceiling that is not level or both you can still get good tight coped joints with a little extra work.

    For the case where you have a ceiling and a wall that do not meet at 90 degrees or a floor and a wall you need to figure out what angle they are actually meeting at. You could use a simple bevel gage or some of the fancier electronic toys they have out there. Either way once you figure this out you can set your bevel and cut a test piece (the longer the better I would say at least 2 feet since the ceiling or floor might not be flat and a longer piece will give you a more accurate fit).

    Once your test piece fits tight against the wall and ceiling or floor with no gaps you have your bevel set and can then set up to cut your 45 degree miter to eventually make your coped cut. So in reality to are making a compound miter with both a bevel and a miter. For crown you may need to do a little more tweaking since you are actually holding the crown upside down and at an angle on the miter saw.

    I have an old house and the walls are not at all square to the floor but using this method I was able to get nice tight coped corners on my stained base board so there wasn't the option of caulk and paint.

    Mike

  8. #18
    Join Date
    Jan 2010
    Location
    Northern Virginia
    Posts
    1,132

    Default Re: Coping Crown Moulding

    A handy tool for fine-tuning copes is a sheet of 120 abrasive glued (spray-mount adhesive) to the face of a scrap of crown; a crown-shaped sanding block. Use one for stain-grade where there's no place for fillers.
    Casey
    Remove not the ancient landmark, which your fathers have set.

  9. #19
    Join Date
    Aug 2007
    Posts
    17

    Default Re: Coping Crown Moulding

    ***!! Thank you all for all of your extremely helpful information! In don't feel like such an idiot seeing how many variables there are in installing crown! After a few glasses of wine and a good night sleep, a clear head does wonders! After uninstalling all of my crown I gave it a final successful try! Taking my time and double checking my cutting directions I realized that I was lining my jig up with the line I had drawn on my fence for a different crown moulding job! Duh! I think maybe having your husband tell you that it should only take me an hour or so to install 4 pieces of crown was a little too much pressure! Lol! Well at least I can say that I have learned a huge lesson and I have actually mastered the art of coping!!!!

    Thanks again to you all!! I always turn to the forum for answers and I always get great advice!

  10. #20
    Join Date
    Jun 2007
    Location
    Coventry, RI
    Posts
    340

    Default Re: Coping Crown Moulding

    Glad to hear that everything worked out for you. I think a lot of people who have never done a project before think it should take a lot less time than it actually does take. It is simple mistakes that will drive us all crazy especially when we are tired. You should post some pics of your handy work for everyone to see.

    Mike

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