I found some MDF CM I want to install. Ceiling and walls drywall. Pretty straight I think. How should I attach it? What type nails or glue? Should I rent a nail gun? Should I predrill the MDF? Must I nail to studs only? Can I hang it myself or is this best left to two people?
Must all inside miters be coped? Must it be coped at all?
Thanks.
Replies
Ive done a lot of MDF crown in the past year, so here's my thoughts.
Definitely rent a nail gun. Trying to nail anything over your head by hand is a nuisance, you won't have set any nails after driving them, you minimize any damage caused by missing with the hammer ( we've all done it ), and the gun nails leave a smaller hole than reg. nails. You should at least catch the wall studs and the ceiling beams where possible. Using a small bead of construction adhesive can help some, but its not entirely necessary.
Unless you have all relatively short lengths, you will need help holding the crown in place. It's a little to flexy to easily manage with one person.
As far as coping goes, I like to cope all my inside corners. MDF copes really easily, just be careful with the coped edges because they can be a little fragile. I think inside miters tend to open up over time and leave a gap thats difficult to fill.
I have had good results with this method. I cut a triangular backing block a little bit less than the hollow area behind the crown. I nail it all along the wall/ceiling corner. then when i shoot nails through the crown I can always hit something. And you can still twist the crown around a bit because the moulding dosnt actually touch the backer.This helps with minor fudging. I miter outside corners as well as inside ones. I always have a scrap test piece with each cut(l-r in or out) To avoid getting a piece too long or short. There are a couple ways to holdup the long end. A springpole or one of the newer telescoping tools (like the 3rd hand) I always glue my miters. Bob
Something I like to do is to turn a piece of base upside down and install it to the wall and ceiling. It is easier to attatch that to studs. Then you can simply install your crown molding to the base trim. Plus, it adds more depth to the crown. Very nice!
You can save time on your mitres by back cutting using a blockplane. Also make 3 jigs 1 outside corner, 1 inside corner, and 1 straight run w/returns on each end. I use these to mark the walls and ceiling to assist w/measuring and placement. W/ long lengths I mark the walls and ceiling in a few spots and tack a few nails to help hold the stock while I fasten it. A long nail (16d) will usually catch the top plate if driven through the center of the crown, but I always try to hit studs and ceiling joists. W/crown a nailgun is the only way to go.
"You can save time on your mitres by back cutting using a blockplane."
Can you explain please?
"Also make 3 jigs 1 outside corner, 1 inside corner, and 1 straight run w/returns on each end. I use these to mark the walls and ceiling to assist w/measuring and placement. "
Do you mean that you make up a small corner (inside or out) then make a mark on the wall and then measure from there? I was thinking accurate marking of long lengths would be a problem.
returns?
If you are going to miter the corners: cut the peices long so they can be snapped in tight. If it is a square room two (oppossing sides) would be cut exact and the other two about 1/8th long. This will help to keep the joints tight but you need to play with the corners as they come together to get them to line up so nail the crown in the center of the room and don't nail any ends till you are done adjusting the crown corners. Also many time when you cut a 45 degree miter the crown has to "roll up" the wall to close the gap (caused by drywall tape and mud) so I have moved to cutting 44 degree miters for inside corners, 46 degree miters for outside miters. This negates much of the problem. Use glue on both miters - the MDF sucks it up. We become by effort primarily what we end up becoming
- Zig Ziglar
So you just mitre the corners and don't do any coping?
On MDF the coped edge will crush under the pressure I put it under, I do cope real woodWe become by effort primarily what we end up becoming
- Zig Ziglar
I like to use the triangle backing blocks.
Some of the Mdf crowns are huge and you will not be able to hit the top plates in between the studs.
the backer blocks allow you to have a place to nail where ever you need to.
Coping Mdf is more difficult than wood.
Get you miters accurate and you can use a little caulk (Heavens NO!!) to fill any minor gaposis.
When doing your mitres make sure both pieces coming into the corner are at the same angle that they are sawn for (the spring angle of your crown).
In the field you may end up twisting a little to get the crown tight which is OK as long as your corners are good.
If you have any odd angles or big crown that needs to be cut flat, or don't know the settings for your mitersaw, get the Bosch angle finder.
Not only will it tell you the saw settings but you can tell if your corners are out enough to adjust your cuts.
If you need to splice in the field the backer will allow you to do it any where instead of just on a stud.
spices will look the best if you don't have to distort the crown to get it to match.
To long and you have to sand and change the profile slightly, which may show up in the wrong light.
A hair or two to short can be filled and sanded smooth to look perfect.
to short is to short and will always look bad.
If you don't do a lot of crown then you should buy a Bosch 12 dual sliding CMS and when you are finished mail it to me!!
May the Carpentry gods smile on your project!Mr T
Do not try this at home!
I am an Experienced Professional!
Remodeling Lead Carpenter w/ 20 years exp.
+ A Construction Engineering Degree
Located in Elmira, NY
For another option..throw up corner block details..no miters , no copes. Makes even a newbie look like a carpenter.
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Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
What exactly are "corner block details"?
you can make, or buy premade..boxes that handle the inside corner, and boxes with a corner cut out for out side corners. They useually have a pendant like lower detail, that "picks up" the design of the crown. They are large enough to engulf the whole edge of the crown so all you do is butt square cuts to them. I will see if I can locate a pic. to post. I am certain that Lowe's or HD has at least one design in paint grade and oak stain grade. They work well in some designs..maybe some else here has a pic. too..
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Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
http://www.imperialdesign.on.ca/ELEMENTS/HandCarving/CORNERBLK/cornerblk.htm
like this..
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Spheramid Enterprises Architectural Woodworks
Repairs, Remodeling, Restorations.
Thanks to all for the good advice.
all of the advice seems that it should help you get your job done. I work alone alot of the time and the way that i install crown molding by myself is by cutting a 10 degree mitre on my butt jointswith the short point of the mitre on the face of the material[crown] that way when i put up the next piece it will be held in place by the slight mitre which will have the 10 degree angles short point on the face.