I have been discussing with an owner and an architect the pros and cons of butt joints vs overlapped miters on crown molding.
One arguement is that overlapping holds better because of more gluing and nailing surface. THe other arguement is that in New England, crown will move and it is better to have a straight joint that can be caulked than a scarf joint that will always be noticable.
I would like to hear the opinions of other industry professionals
Replies
We used to overlap and use a backboard (12") glued to the crown's backside. This way it was nailed and glued. Also, have the angle of the cut facing away from the room's main light source. This way when the light catches the crack it is not casting a shadow.
Now we use butt joints and biscuits. Seems to work the same and is much faster.
Season also matters. When installing in Summer we fit mouldings super tight. In the winter, just snug.
With you all the way Frankie - still use the backer if we're doing the glue-up on the floor..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
I do a double 30. Thirty degree bevel, thirty degree miter. Toss in a biscuit or two, depending n the size of the crown, as well as a small backer...again, depending on the size of the crown.
As he previous poster wrote, I also run the bevel away from the light source (artificial or natural) or the main viewing angle, depending...
I'm also in New England.
Tried using biscuits with the double scarf: really had trouble getting the biscuit slots to align. Know a trick ?
Guy I work with uses dowels, but they're drilled in the shop (crown and base are delivered to the site with one end machine coped too). .
Phill Giles
The Unionville Woodwright
Unionville, Ontario
I've never tried biscuits on a compound miter, so I may be blissfully ignorant of some ot the difficulties....
However, it would seem that all you'd have to do is index the bicuit location to two known surfaces. For example, a given distance from the smooth back of the crown, and a given distance from one of the two long edges.
Like I said, I've never tried it myself.... so what happens in reality? <G>
Ragnar
Well, you have to tilt the fence down 30 for one cut and up 30 for the other, that seems to introduce some error. Plus it seems that you have to oversize the slots (deep and long) to get it to assemble..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
Ah.... I see what you mean. If you don't get the face of the jointer against the bevel angle, the cut will end up too shallow.
Maybe if you used a larger diameter cutter (i.e. 3-wing cutter on a router) you'd be able to get enough depth to ignore the bevel angle, and just cut the slot normally.
I just picked up this months copy of the magazine, theres an article in there about hanging crown, the author seems to do all the above, scarf, biscuit, and a backer board behind the joint.
The one point the author made that I was taught is to pre glue your scarf.
Anyway seemed like a good article if your interested
Arrived in my box this evening too - I see he uses much shallower bevel/mitre angles, registers the height from a table-top, and basically ignores alignment by cutting a 20 hole for a 0 biscuit..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
A properly glued scarf joing shouldnt be noticable even if there is movement in the house. A lot of times a fully cured glue joint is as strong as the rest of the wood. Use a high quality wood glue and like someone suggested above back the joint up with a piece of wood in back of it to make it stronger.
Just my 2 cents
I follow suit with previous posters...always a scarf joint. Never seen a butt joint hold tight enough that caulk made it invisible.
J. D. Reynolds
Home Improvements
"DO IT RIGHT, DO IT ONCE"