Crown Molding is a beautiful upgrade that just about any handy homeowner  can manage.  The transforming affect that crown molding offers to a  room is something that you will appreciate every time you step through  the front door.  Crown will soften a boxy room and bring a touch of  class to your unique style.  With all the positive attributes to crown,  there are some hurdles that the inexperienced DIY'er needs to be aware  of before venturing out into the crown molding aisle.  
First of all, you have to get the molding home.  Finger-joint pine and  MDF moldings come in 16 foot lengths.  That definitely won't fit in the  Honda or even a minivan!  If you do have a way to transport 16 foot  boards keep in mind that mdf will weigh about twice what the pine will,  and holding that above your head while trying to nail into the wall can  be a daunting task.  Polyurethane crown moldings come in much more  manageable 8 foot sections but still weight as much as mdf.  Foam  moldings come in 6.5 foot sections and are so light that installing is  just plain easy.
Tools, tools, tools!  Installing wood, MDF and PU crown requires a  plethora of tools.  If you are trying to build up your wood working  garage then grab that credit card head to Home Depot!  If you just want  crown molding in your dining room and don't want to be the next Bob  Villa, then consider EPS foam moldings.  Installation is done with  caulking, so no nails, no need to find studs, no need to put up a backer  board, no cracks in the plaster, no nails penetrating plumbing and  wiring, no easier method to installing crown.  If you can place a  section in a miter box and cut through it with a hack saw, you can  install foam moldings.  The beauty is that once it is up and painted you  have not given up anything over wood moldings.  Actually you will save a  boat load of time and money. 
Corners.  Face it they are a pain in the neck!  If you don't have to cut  corner, don't,  With wood products and PU, the corners have to be cut  on-site.  Most home construction is not done in perfect angles.  Corners  are usually off by a few degrees and that needs to be addressed during  install.  This is also the case with foam moldings but the difference is  that foam is a forgiving material so removing a little material form  the corner is an option when the corner is not perfect.  Foam moldings  come with precut corners and with a little forgiveness in the material,  some fudging by the installer and a little caulking in the seam, it is  not hard to get a perfect corner every time
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Painting  Crown can be almost as hard as installing it.  Fortunately just about  everything comes pre-primed or paint ready.  MDF is usually comes with a  coat of primer.  Painting is done after install because nails tend to  leave holes that need to be filled with puddy and sanded.  Polyurethane  comes with no primer and needs paint but also has to be painted after  install because of nailing.  Keep in mind that PU is extremely smooth  and either needs some primer or some sanding to get the paint to stick.   Not an easy paint project.  EPS foam comes paint ready and is bright  white.  You can paint after install or before.  No nail holes to contend  with just corners and seams.
Seams are the one thing with PU and Foam that people worry about.  MDF  and its 18 foot lengths facilitate fewer seams but create a colossal  amount of waste.  Seaming with PU is a fomidable task and currently  there is no product out there made for seams on polyurethand.  Seams  with EPS foam is rather basic.  If for some reason you do have a seam  that is noticeable after install and painting then a little dab of nail  hole filler or dry wall Spackle (not the lightweight stuff) and some  sanding will make that seam disappear.  Sand with some 400 grit and  repeat if necessary to hide.  Foam doesn't expand or contract so once  that seam or corner is fixed it is fixed for good.
This seams like a lot of information for such a simple project but it is  good to know the facts.  A typical customer install of foam crown takes  about 2 hours.  According to Home Depot, MDF crown molding is one of  their biggest return items.  To drive to the hardware store, purchase  MDF take it home and then return it back to the hardware store, wait in  line for your refund and go back home, takes about 2 hours.  I tell you  what, order EPS crown online at www.SoSimpleCrown.com, they will ship it  to your door with pre-cut corners, and the time it takes you to go to  Home Depot and back, twice, your crown molding project will be done!     Now you can enjoy your weekend 
and your cozy home!