Introduction: Alcove Update With MDF and Moldings

About: I'm a Houston, TX carpenter teaching beginners and hobbyists how to develop a Builder's mindset in their shop, their lives, and beyond.

In this tutorial I'm going to show you how I used cheap 3/4" and 1/2" MDF and store-bought moldings to renovate this entry way alcove for a huge update. I won't go over paint selections just because there are so many out there, it's best to ask your local paint store what they recommend for a finish coat, but I've got you covered on primer (pun intended).

Hand Tools:


Utility Knife

Small Pry Bar

Adjustable Pliers

Tape measure

Kreg Pocket Hole Jig

Quick Clamps

Wooster Paint Brush

Power Tools: You can get around not having most of these tools or substituting for cheaper tools. The problems you'll have are getting around the regular drill (for use with the Kreg Jig) and the nail gun. If you at least have the drill you can pre-drill the holes in your trim and hammer in nails, then set them with a nail set.

Air Compressor

18 Gauge Nail Gun

Brad Gun

Dewalt Drill

Dewalt Hammer Drill

Table Saw (can be done with circular saw)

Cross Cut Sled for Table Saw (DIY)

Shop Vac Miter Saw (can be done with miter box)

Crown Cutting Jig for Miter Saw (DIY)

Caulk Gun


3/4" MDF (I also substituted in some scrap 1x3 pine in a couple of places)

1/2" MDF

3/4" trim molding

Crown molding

Wood Glue

3/4" brad nails

2" 18 GA nails for nail gun

1 1/4" 18 GA nails for nail gun

2" drywall screws


Sand-able Primer

220 Grit Sand Paper

Trim Paint

Prep: Protecting the floor: When I did this project I was in the middle of replacing all of the baseboards in the entry way so I already had paper taped down to the floor with painter's tape. You can really use whatever you have like old towels or a tarp. You're trying to catch dust and paint and protect the floor in case you drop a tool. Don't pretend you don't drop tools like I do...

Step 1: Remove the Bottom Trim

You'll need to use a sharp utility knife to score the outside of this bottom trim piece, otherwise when you try to pull the trim you'll end up ripping the drywall paper. Once you've scored all around the trim, take a knife or a painter's multitool and hammer it up under a bottom corner. Start to pry the corner away from the wall a little at a time, working your way along the bottom of the trim piece. Eventually it will pry off the wall and you can pull the whole thing off without damaging anything. Go ahead and mark a 3/4" MDF strip to width so you can cut it and install it later.

Step 2: Build the Inside and Outside Trim Assemblies

Inside Assembly: 1/2" MDF

Rip some strips of 1/2" MDF on the table saw to make the inside trim. I ripped mine to 2 1/2" wide, then cut them to fit just inside the alcove, held together with screws. You could also use nails and glue if you're careful. This is going to be the inside assembly.

Outside Assembly: 3/4" MDF

Rip strips of 3/4" MDF on your table saw, I ripped mine to 3" wide for the sides and 2" wide for the top of the "Outside Assembly" or "face framing." I wanted the face frame to stick into the alcove by just a 1/4" in from the inside frame. Basically, if you stick your head in the alcove, I want you to see a 1/4" lip on the back side of the face frame. Cut your strips to the size you need and get ready for assembly.

I used my Kreg Pocket Hole Jig to pre-drill screw holes that will hold the face frame together since the frame pieces will be connected edge to edge, unlike the Inside Assembly. I decided to drill the pocket holes in the top strip, but you can do it whichever way works best. You'll have to adjust 2 things based on the thickness of the material: The tabs on the Kreg Jig and the collar on the drill. Otherwise you won't drill the holes deep enough your you'll drill all the way through. Not good.

Once the holes are drilled rub some glue where the pieces of the face frame will meet before clamping everything in place with adjustable clamps. Check the Kreg Jig chart to see which length of screw you need to use, in this case if you're using 3/4" thick MDF you'll need 1 1/4" pocket hole screws.

When you drive the pocket hole screws in, use some force. This is not a "let the tool do the work" scenario. If you don't take charge on this part the screw won't bite into the second piece well and it will mess up the look of the face frame. Take charge!

Step 3: Dry Fit the Two Frame Assemblies

Unfortunately nothing is 90 degrees in homes just because of how framing and drywall are applied. It's no one's fault (usually). But it does mean that if you're trying to be exact and you attach the face frame to the inside frame without dry fit testing them first, you'll end up having to hammer your assembly into place.

First set the Inside Frame Assembly in place, then the Outside Assembly face frame exactly where they'll go and mark where the two meet on the back side of the face frame. This is where you'll attach them so everything will slide smoothly back into place once it's one big unit.

Step 4: Combine the Inside and Outside Frames, Install

Lay the Outside frame face down on the table and match the Inside frame up to the back side where you marked it out last step. Use wood glue to attach the two frames together. You can use brad nails to secure them will the glue dries.

Once the glue has dried, carry the whole assembly back to the alcove and put it in place. It should fit in smoothly since you took the extra time to line everything up. You might want to use some construction adhesive on the back side of the frame just in case, but I skipped this step. Use your nail gun with 18 gauge nails to install it. Shoot some through the face frame into the wall and some through the inside frame into the wall.

Step 5: Cut and Assemble the Head Casing

Main Body: 3/4" MDF

Rip 3/4" MDF on your table saw to make the main body of the head casing. I ripped mine at 7" tall. Cut it to the same width as the face frame you just finished installing in the last step. Next rip MDF into a skinny strip for the bottom of the head casing and a bigger strip for the cap on top. I wanted a 1/2" reveal on the lower strip so I cut it at 1 1/4" wide (1/2" reveal plus 3/4" thickness of MDF frame). The top cap I cut so that when I install my crown molding I'll have a 1/8" reveal. My crown molding sticks out 1 3/4", plus the 3/4" thickness of my MDF head casing, plus my 1/8" reveal so I ended up cutting 2 5/8" wide. Cut it to length leaving enough room for the crown molding plus the reveal as well.

Trim on Top and Bottom: 3/4" Molding

I bought my moldings from Lowe's, but you can get them wherever you want. The molding is 3/4" tall so it matches the 3/4" MDF perfectly. This is where the Miter Saw and my Miter Saw jig comes into play. You can cut the molding without the jig, but in my experience my Miter Saw eats the end of the molding and shoots it across the shop. The jig keeps everything in place and minimizes projectiles. You'll be cutting molding to cover the three exposed sides of the bottom and top caps. Set your Miter saw to 45 degrees to make the cuts. I usually cut a little bit longer than where I mark, then cut a tiny bit off at a time to make it fit perfectly.

Attach your moldings to the caps with glue and your brad nail gun. Make sure to get the glue in to the 45 degree cuts on your moldings so the corners are nice and strong. Last step on these is sanding any rough edges on the moldings, hit everything with 220 grit sandpaper.

Attach the Top and Bottom Caps: Glue and Screws

If you have a drill it for counter-sinking screws this is the place to use it. You can also just use your nail gun, but I get scared my nails are going to make a turn and poke out the head casing. Use a bead of glue between the caps and the head casing before attaching them with your choice of screws or nails. You now have the head casing assembly done, we're moving on now to the crown molding. You'll see why that's not part of the head casing assembly in this tutorial.

Step 6: Make an Assembly Out of the Crown Molding

Using your Miter Saw and jig, cut the crown molding to fit around the head casing. Once you've cut your three pieces, go ahead and dry fit them in place to make sure they fit properly. Then take them off to be assembled separate from the head casing. The reason I'm not immediately attaching the crown molding to the head casing is so I can hide some screws behind the crown molding. I want to make sure the head casing is attached solid to the wall.

Use glue and your brad nail gun to pre-assemble the crown molding off to the side. This also helps make sure the joints on the crown molding will be perfect no matter the condition of the head casing.

Once the crown molding is assembled, go ahead and drill some holes in the head casing to prepare it for the screws that will hold it to the wall properly. Then carry everything back over to the alcove.

Step 7: Install the Head Casing, Crown Molding


If you've got it on hand, use construction adhesive for this step. It scares me to think of someone up on a ladder grabbing onto the head casing for support and it comes off in their hand so make it stick! I ended up using wood glue because that's what I had on hand, but I'm also using plenty of drywall screws too. With the adhesive applied to the back of the head casing, hold it in place and drive your drywall screws through into the wall.

Crown Molding:

Take your crown molding assembly, add some glue to the top and bottom where it will be in contact with the head casing and the cap, and attach it with 18 gauge nails from your nail gun. Try to remember where the screw heads are and DON'T shoot one with a nail, it's not pretty. Also, wear protective glasses, I've been hit in the eyelid with a nail that took a bad turn. That's too close, wear your equipment.

Bottom Molding:

Remember that bottom piece we cut forever ago? Put some glue on the back and tack it in place with 18 gauge nails from your nail gun.

Step 8: Fill Nail Holes With Spackle

I use the product in the picture that goes on pink and turns white when it dries. Helps me see what's fresh and what is dry enough to sand smooth. Wipe a little spackle on all of the nail holes including the nail holes from the tiny brads in the moldings. Trust me, primer and paint won't hide anything, you need to use spackle. You might also want to apply spackle to any of the MDF edges because it will save you money on primer. Work the spackle into the end grain of MDF with a drywall knife if you have one, or a putty knife.


You should be wearing a respirator with this stuff to begin with, but even now when you're really just trying to sand the spackle you should still wear stuff to protect your lungs. Grab your 220 grit sandpaper and sand all of the spackle so it's smooth. Add more spackle to any areas that didn't fill in all the way and sand those areas again. The end grain that you covered in spackle will put out a ton of white powder so keep a vacuum handy.

Step 9: Prime With a Sandable Primer

There are a lot of different primers out there, some of them can be sanded smooth and those are the ones you want. The primer in the picture is the best one I've ever used, it bites into any surface I put it on and sands super smooth. Sherwin Williams Wall & Wood Primer is the best thing for trim work. Using your high quality paint brush, apply a single coat of primer over every surface, and don't worry if you get any on the wall, just feather it out so it doesn't run. Make sure you get a good coat on the edges of the MDF that you coated with spackle in the last step.


Use your 220 grit sandpaper again to sand every surface smooth. Be careful with the corners that you don't sand all the way down to the bare MDF, you'll need to re-paint them with a little bit of primer again before putting on the final topcoat.

Step 10: Caulk and Apply the Top Coat, Wall Paint


You want to make sure that whatever caulk or silicone product you use is PAINTABLE. It should say "paintable in 30 minutes" or something like that. If you get non paintable caulk you'll have to pull all of it back out with a putty knife and reapply the right stuff. Trust me, the non paintable stuff is specially formulated to be slick, it won't work. Run a bead of caulk along between the trim work and the wall and wherever two pieces of trim or molding come together. Keep a damp rag on hand for when you use your finger to push the caulk into all of the joints.

Top Coat:

You'll need at LEAST 2 coats of paint as a top coat depending on the brand. Sometimes it pays to do 2 coats of whatever color you want, then a clear coat on top of that. 1 coat of paint won't protect your work and it won't hid any variation in your primer coat. Also, avoid the temptation to paint with thick paint like the primer + paint one-coat brands unless you want to see every single brush stroke. For some paints it may even be valuable to add an "extender." For example, if you're using an oil based paint, you will sometimes want to use a specially formulated extender to extend the drying time of the paint. The idea is that you have more time to brush on the paint, then brush over any areas where two brush stroke directions come together like in corners. It also give the paint more time to "self-level" meaning that your brush strokes start to disappear while the paint is still wet because it levels out a bit. Ask your local paint shop what they recommend as a top coat, they can at least point you in the right direction.

Wall Coat:

Use whatever wall color paint you want to cut in around the new trim work. This is the final step and it really makes the work pop out from the wall. Pick up all your tools, take the painter's tarp off the floor, let it dry, and throw in some color in the form of a floral arrangement or whatever. Congratulations!

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