Crown molding is one of the most underestimated (and beginner friendly) dwelling renovation projects anyone can undertake to upgrade the visual impact of a room. Cove molding adds flair and personality to a room, and shows that thought has been taken to specifically make a home more visually alluring. They brightens a room by radiating light that would otherwise just die in a dark corner brightening up the room as a whole. It also (sometimes subconsciously) increases the perceived warmth of a room by softening the sharp corners where the wall and ceiling intercept. It is important to know the details of how to crown molding to have everything pre-planned so that you can get the cornice molding installed as quickly and smoothly as possible.
Material
There are a few different materials when it comes to crown molding, each having its own advantages and weaknesses. Wood cornice molding is the most common and has been around for centuries. Unfortunately, it is hard to make seamless and tends to crack in the first year or two after being installed, requiring repairs. Plaster moldings are gorgeous and used on upscale homes, but are burdensome and typically require a skilled trade person to install.
There is a new molding material out there that uses expanded polystyrene (EPS/styrofoam) coated with a mixture plaster of paris / drywall compound. Coated styrofoam cornices are more flexible than wood, and simpler to join and make uniform so you do not have to touch them up after a year or two. These styrofoam crown moldings give the look of costly plaster cornices, but at a sliver of the weight. Because of the light weight, they are far easier to install as well using only drywall compound, you can press them into place and leave them. They will be the focus of this guide.
Planning
You want to ensure you do not have any important occasions happening around this renovation. Most (actually, all in my experience) renovations end up taking 50-100% longer to complete than the home owner is expecting. Installing styrofoam crown molding around the room is no exception. To figure out how much cornice molding is required, measure the length of the walls where the styrofoam cove molding will be placed from corner to corner. There are 2 ways of knowing how many pieces of molding will be needed the first is to add 10% to the total of wall the walls (e.g. 12' x 15' x 12' x 15' = 54' + 10% = 59.4' = 60')... and the second is to divide each wall by the length of each molding piece (e.g. for 8-foot molding lengths: 12' / 8' = 1.5 pieces, which you would round to 2, & 15' / 8' = 1.8 pieces which you would round to 2, thus 2 + 2 + 2 + 2 = 8 [8' pieces]). The second method is more accurate to assure that you have enough and do not risk running short, but as you can see with either method, you are picking up 8 pieces (for this example).
You want to ensure you have a dry, airy room to store your molding.
Double checking you have the right tools will make the whole process much easier as well. Make sure you have:
1. New Rag (to prepare wall surfaces)
2. Drywall compound and putty knife
3. Miter box + Handsaw (so that you can cut the right angle, smoothly)
4. Step ladder (tall enough so you can easily reach the ceiling)
How To Cut Crown Molding
Non Woven Mask Manufacturers Always follow good safety procedures use gloves to handle materials, goggles when chemicals can get into your eyes, and a respirator mask when sanding and patching. Make sure you wear some old clothes that you do not mind becoming ruined.
Always move furniture away from the walls and protect them, so that you have unblocked access to your working area and your furniture does not get ruined. Prep the corner of your ceiling and wall where the styrofoam cornice will be placed from dirt by going over it with a moist cloth, and allow it to dry before installing the cornice.
I hear (and say) this so frequently that it is completely cliche but it must be said Measure twice, cut once! This applies to styrofoam cornices as well! On the day youre installing crown molding, make sure to measure everything again. This will keep you from wasting a $30 piece of trim because you cut it incorrectly.
It is best to start your styrofoam crown molding installation behind the entrance to the room, so that the most visible portion is sure to have the least number of joints. When you get to a corner, you will need to use your miter box to cut the molding at a 45 degree angle. To use the miter box, ensure the ceiling edge of the crown molding is along the bottom of the box, and the wall edge of the molding is along the side of the box opposite from you (so that, it is upside-down). Dry fit the two ends of the pieces into the corner prior to installing in place to ensure a decent fit.
No corner is ever 90 degrees unfortunately, and you may have to play with sandpaper or fill with drywall compound to join the two pieces together properly.
How To Install Crown Molding
Using your drywall compound, apply a fair amount to the molding along the ceiling and wall contact sides. Carefully move into place with the molding and press the cornice against the ceiling and wall simultaneously. Drywall compound should queeze out a little use your cloth to wipe it clean. At this point, the drywall compound should be able to hold the styrofoam crown molding on its own, and you can release it. If you want extra security to ensure the molding stays in place, you can use a small nail at 1' from each end, as these penetrations can be easily repaired using the drywall compound when removed during the touch up stage. Apply drywall compound to the sides of moldings before butting them up against one another, cleaning the drywall compound as it squeezes out when pressed together. Leave the trim in place to dry for 24 hours.
After 24 hours, you can re-touch the styrofoam crown molding using drywall compound, and smooth out any excess drywall compound using a fine-grit sandpaper. Because molding looks different depending on lighting (natural -vs- interior lights) you may want to check up on the room at times during the touch-up day and try all the different light settings you will be using.
