Introduction: Catacomb Wall Panels

About: Part-time gardener, tinkerer, and putterer. Should not be left unsupervised around power tools.

When it comes to decorating my house for the holidays (Halloween, Christmas, Arbor Day, etc.), I am faced with a major challenge --the lack of the most common area to put decorations in the United States, i.e., a front yard.

This year, instead of draping spiderwebs down the front of the house and calling it good enough, I decided on upping my game a bit and built a cemetery tableau in one of the flowerbeds along the driveway. The ivy-covered wall of my neighbor's garage made the perfect backdrop, but it needed something to really make it stand out a bit more. Looking around at what existing props and materials I had on hand and a few notepad doodles during meetings later, skull-studded catacomb walls seemed like just the thing. My only design limitations were that it had to be lightweight and easy enough for one person to transport and set up, weather resistant, and it had to be less than six and a half feet tall -- the maximum height anything can be to stand up in my basement without hitting the floor joists above.

Wandering around Home Depot one August afternoon, I ventured to the farthest aisle and struck gold. Or more specifically ... foam! The wall backs and stones are sheets of foam insulation and the skulls and mortar are expanding spray foam. Not only were the foam sheets lightweight and durable enough to withstand whatever hurricane, Nor'easter, or unseasonable blizzard that visits coastal New England during October, but the panels were available in 4' x 8' and 2' x2' sizes, which means I would have to do minimal cutting for two 4' x 6' catacomb panels.

If you made it this far, I thank you. Please bear with me for a little while longer as I do my best to walk you through the steps it took to get from notepad doodle to finished product.

Step 1: Things You Will Need


  • Expanding spray foam
  • 1" thick foam insulation panels
  • Plastic skulls
  • Paint (both spray and acrylic)
  • WD-40 and/or cooking spray
  • 2' sections of PVC pipe in 1/2" diameter and 3/4" diameter
  • plastic cling wrap
  • bungee cords (depends on setup location)

Tools used:

  • paint brushes
  • Bread knife
  • Electric carving knife
  • Hot glue gun

WARNING: As this project makes use of sharp instruments, tools that can give 3rd degree burns or start fires, and materials that give off brain cell-killing fumes, please take care to not injure yourself or others.

Step 2: Let's Make Some Skulls

Start off by cutting the plastic skulls open to create molds for the foam skulls. I had a few already cut open from a project earlier in the year where I used them for molds to make hypertufa (a lightweight mix of Portland cement, peat moss, and perlite) skulls around the garden. Cutting the skulls at different angles will give some nice variety when the foam skulls are mounted. Once you have a sufficient number of molds, spray the inside with a light coat of WD-40 or cooking spray to keep the expanding foam from sticking to the molds.

Begin spraying the expanding foam carefully inside the molds, making sure to cover all the nooks and crannies. Slowly build up the walls of the foam skull in layers. It's not necessary to fill the entire mold with expanding foam, unless you want a solid foam skull. I was able to get approximately 7 skulls out of one can of expanding foam by making them hollow. Giving the foam a light misting of water will aid it in expanding to its greatest capacity.

Once your molds are full or you have run out of expanding foam, or the straw is either broken off or filled with solidified foam, set them aside open side up to cure for approximately 24-48 hours. Make sure to put them in a place or on something where you don't care if spray foam gets on it.

Check on your molds after 24 hours. The foam exposed to the air will have hardened, and you should be able to pull the skulls away from mold slightly. You can pull the skulls out of the molds completely at this point, but there will most likely be uncured foam pooling in the bottom of the mold. If you can hear a faint crackling noise when you pull the foam skulls out, that's a good signal that they're not quite ready.

Step 3: Now Let's Paint Them

First give the skulls a good base coat of a dark-colored paint. I alternated between a dark brown satin spray paint and basic matte black spray paint. If you plan to use spray paint, please do it outside or in an area with good ventilation.

Once the base coat has dried completely and you are satisfied that they no longer look like they're made out of expanding foam, take a moment to admire your handiwork as you begin to wonder just what color old bones actually are.

Hours of looking at reference materials on the internet will reveal that old bones can be any number of colors, from bleached white, to browny-yellow, to mossy green, or even kind of reddish. Using basic craft store acrylic paint, I mixed up a few colors composed mainly of mustard yellow, suede, ivory, grey, and dark tan.

To paint the skulls, I went with a flat 2" paint brush, and with very little paint on the brush, gently dabbed and drybrushed it on. In case you're not familiar with drybrushing, that is a painting technique were you take a flat brush with very little paint on it, and with gentle, even strokes drag it across whatever you are painting, letting the paint highlight raised surfaces and details.

Step 4: We're Gonna Build a Wall

Using one sheet of foam board insulation is preferred for the sake of stability. In my case, each panel consisted of half of a 4' x8' board (so 4'x4') with two 2'x2' hot glued on top. When using hot glue on foam boards, make sure the glue is hot enough to be able to work with it, but not hot enough to melt through the foam. Because it will.

Next, fashion field stones to be glued to the wall. I used a bread knife to cut the rough shapes, and then an electric carving knife to shape them. When you're satisfied with your faux stones, hot glue them to the wall panels.

After the stones are secure, lay the panels down if you have not done so already. Wrap your skulls in plastic cling wrap and arrange them on the wall panels. Wrapping the skulls will protect them when it comes time to paint the walls.

Once your wrapped skulls are distributed, grab several cans of expanding foam and start spraying down the "mortar" that cements your wall together. This can be tedious work, but going slowly will give you greater control over the outcome. When spraying around the skulls, build up the foam a bit to hold the skulls in place. Spritz the foam with water and let it do its thing.

Step 5: We're Gonna Paint That Wall

After the expanding foam hardens completely, you should be able to remove the plastic-wrapped skulls pretty easily. If not, it's a good thing you wrapped them in plastic. If you do remove the skulls, use your photographic memory to remember where each one goes, or do like me and use a marker to number each skull and corresponding hole. Taking a picture would also work if your skulls don't all look the same.

With your skulls are removed and numbered or securely wrapped, take your wall panels outside or to a well-ventilated area, and lay down a nice base coat of matte black spray paint, as you originally did with the skulls.

Once the base coat is dry, use textured spray paint to give the wall panels a more stony appearance. I used grey "granite" spray on the stones and brown and tan on the mortar.

When your latest round of painting is dry, unwrap the skulls and affix them back in place with hot glue. If there are gaps around the skulls, use some expanding foam for its intended purpose (for once) and fill in those gaps.

After that expanding foam dries, paint it to match the rest of the wall. I mixed a dark grey acrylic paint that matched pretty well.

Step 6: We're Gonna Put Some Finishing Touches on That Wall

Once that last round of painting had dried, I drybrushed/dabbed acrylic paint onto it to blend it in with the spray painted stone texture parts, plus some mossy green and reddish brown to bring in a bit more color.

Finally, I hot glued a 2' length of 3/4" PVC pipe to both side edges of each panel. These pipes snugly slide over the 2' sections of 1/2" PVC pipe that were driven halfway into the ground as anchors. Once in place, I used 4' bungee cords woven through the ivy vines and hooked onto the sides of the panels.

Step 7: Glamour Shots / Final Thoughts

Apart from helping my friends the last few years with their yard decorations, this was the first time I built something that I would consider "large scale" for my own house. I started in mid-August and finished the week before Halloween, but that's mainly due to me only giving it an hour or two after work a few times a week and having to stop and figure it out as I went along.

Even with the bungee cords strapping the panels to the ivy, the right-hand panel broke free during the almost-hurricane that blew through the area a few days before Halloween, snapping one of the PVC anchors clean off the side of the panel. For next year, I am going to re-do the PVC on the sides, running it the full 6' height.

What I like about this project is not only is it lightweight and easy to move and assemble, but it has the potential of being a modular design using PVC pipes attached horizontally and vertically on the back much in the same way the ground anchors work. Using this method, it would be easy enough to create a horizontal panel across the top to make a lintel or arch. Taking them indoors, these catacomb wall panels would be a great backdrop for Halloween party photo booths.

Step 8: Bonus! Headstones

Both wall panels were barely in place before I decided that something had to be done about the cheap dollar store Styrofoam headstones that barely last from one year to the next.

These four are carved from leftover foam board, so they're a lot sturdier. The first one I used a skull stencil for the design, the second one is based on more traditional Puritan funerary motifs, and the last two are copied from actual colonial-era headstones here in Massachusetts. For those two, I printed out high-resolution images and then copied them onto the foam board with carbon paper. All four were carved using a utility knife to score and chip out pieces, and a soldering iron was used for the lettering on the last one. After using the bread knife/electric carving knife combo to roughen up the edges a bit, they were given a base coat of matte black spray paint and then drybrushed with a few different shades of grey.

Thank you for reading!

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