Foam crown moulding goes up with adhesive, a mitre saw and a few brad nails. Cut your corners with the moulding upside down against the saw fence, glue it where the wall meets the ceiling, and fill the joints with caulk. Most rooms take a day, and it's light enough to do on your own.
This guide covers the part most people get stuck on, which is corners, plus how to pick a size and how much to order.
Pick the right size first
Crown looks best when it suits the ceiling height. Too thin on a tall ceiling and it disappears. Too big on a low ceiling and the room feels squashed. A rough guide:
| Ceiling height | Crown height to look at |
|---|---|
| 8' | 3" to 5" |
| 9' | 5" to 7" |
| 10' and up | 7" and up, or a built-up profile |
This is a rule of thumb, not a law. If you're between two sizes, go bigger. Order a $15.50 sample and hold it up in the room before buying the full run.
Our ULTRAlite plaster-coated EPS crown comes in 8' lengths. Most profiles come in several heights, for example ME-IN-M003 in 5", 6" and 7", from $31.25 a length at time of writing. Browse all ULTRAlite crown profiles.
How much crown to order
- Measure the length of every wall where the crown will go.
- Add them up and add 10% to 15% for cuts and mistakes. Rooms with lots of corners need the higher number.
- Divide by 8' and round up.
Example: a 12' x 14' room is 52' around. Add 15% and you get about 60'. That's 8 lengths.
Order all of it at once. One shipment costs less per piece than two, and 8' lengths ship by courier, not freight.
Tools and materials
Tools
- Tape measure and pencil
- Power mitre saw, or a mitre box and a fine-tooth hand saw
- Coping saw (optional, for coped inside corners)
- Caulking gun
- Brad nailer, or a hammer and brad nails
- Utility knife and a sanding block
- Stud finder
- A scrap piece of crown for test cuts
Materials
- Crown moulding
- Construction adhesive. We recommend PL Premium
- Paintable acrylic caulk
- Paint. ULTRAlite crown comes paint-ready, no primer needed
Watch the adhesive. Some solvent-based adhesives can melt foam. Stick with PL Premium, or check the label says it's safe for foam before you swap in something else.
Step 1: Mark a guide line
Hold a scrap of crown in place, tight into the corner between wall and ceiling. Make a light pencil mark on the wall along its bottom edge. Do this every few feet around the room, then connect the marks. Now every piece sits at the same height, even if the ceiling dips.
Step 2: Start with the longest wall
Put up the longest wall first with square-cut ends that butt straight into the corners. Every inside corner after that gets cut to fit against this piece. It's the easiest way to keep the whole room tight.
Step 3: Cut inside and outside corners the easy way
This is where most people give up. The trick that makes it simple is cutting the crown upside down and backwards. You never have to work out a bevel angle.
- Set the saw to 45°. No bevel.
- Put the crown on the saw table upside down. The edge that goes on the ceiling sits on the saw table. The edge that goes on the wall rests against the fence.
- Hold it at the same angle it will sit on the wall. Both flat backs should touch the table and the fence. A strip of tape or a block on the table helps you hit the same spot every time.
- Cut.
Which way to swing the saw
| Corner | Piece | Saw angle | Keep this side |
|---|---|---|---|
| Inside | Left piece | 45° right | Right side of the blade |
| Inside | Right piece | 45° left | Left side of the blade |
| Outside | Left piece | 45° left | Right side of the blade |
| Outside | Right piece | 45° right | Left side of the blade |
Easy way to remember it: because the crown is upside down, a piece that goes on the left in the room is always the part you keep on the right of the blade, and the other way round.
Cut a test pair on scrap first. Hold them up in the corner. If there's a gap, the wall isn't square. Adjust the saw a degree or two and cut another test pair until it closes.
Step 4: Cope inside corners for a tighter fit (optional)
Walls are rarely a perfect 90°. A coped joint hides that better than a mitre.
- Cut an inside mitre on the piece as in Step 3. The cut exposes the profile's outline on the face.
- Run a pencil along that outline so you can see it.
- Cut along the line with a coping saw, angling the blade back so the back of the piece is cut away more than the face.
- Test fit against the square-cut piece on the wall. Sand or trim until it sits tight.
Foam cuts easily, so a sharp utility knife works for small trims.
Step 5: Glue it up
- Run a bead of PL Premium along the top and bottom flat edges on the back of the crown. Don't cover the curved face in between.
- Put a little adhesive or caulk on the cut ends at every corner and joint.
- Press the piece into place on your guide line.
- Pin it with a few brad nails into studs or joists to hold it while the adhesive sets. On a light profile, painter's tape can hold it instead.
- Wipe off any squeeze-out right away with a damp cloth.
Step 6: Joining two lengths on a long wall
On walls longer than 8', you'll need a joint.
- Cut both ends square, or at matching 45° angles so they overlap (a scarf joint). A scarf joint hides better.
- Put adhesive on both ends and push them tight together.
- Try to land the joint over a stud so you can pin it.
Step 7: Caulk, fill and paint
- Run a thin bead of paintable caulk along the top and bottom edges where the crown meets the ceiling and wall. Smooth it with a wet finger.
- Fill corner and joint gaps with caulk. Fill nail holes.
- Let it dry, sand lightly if needed, then paint. ULTRAlite crown is paint-ready, so no primer.
Caulk is what makes a DIY job look professional. Don't skip it.
Tips from the shop
- Buy one extra length. A spare piece costs less than a second delivery if a cut goes wrong.
- Label every piece. Write which wall and which end it goes on the back.
- Measure at the ceiling line, not the floor. Rooms are often a little out of square top to bottom.
- Go bigger on a tall ceiling. A 7" or 8" profile reads better on a 10' ceiling than a 4" one.
FAQ
How do you cut crown moulding inside corners?
Put the crown upside down on the saw, ceiling edge on the table and wall edge on the fence. Set the saw to 45°. For the left piece of an inside corner, swing the saw right and keep the right side. For the right piece, swing left and keep the left side. Cut a test pair first.
Do you need to nail foam crown moulding?
The adhesive holds it. A few brad nails or some painter's tape just hold it in place while the adhesive sets.
What glue do you use for foam crown moulding?
We recommend PL Premium. Some solvent-based glues can melt foam, so check the label before using anything else.
Can I install crown moulding by myself?
Yes. Foam crown is light, so one person can handle an 8' length. A second person makes long walls faster.
How much crown moulding do I need?
Add up the wall lengths, add 10% to 15%, then divide by 8' and round up. A 12' x 14' room needs about 8 lengths.
Planning a room? Shop ULTRAlite crown moulding, order a $15.50 sample, or send your room sizes and ceiling height to customercare@foamcore.ca for a quote within 24 hours.
