Introduction: Make a Troll Cave for Your Boss

About: I work in a hardware store and lumberyard, which gives me all kinds of inspiration and resources. It's also like being a therapist, as I convince people to do things the right way, give them confidence and ins…

Our boss got moved to a little space under the stairs; this was actually good as it gave him more privacy from being interrupted on the retail floor, but it was a cozy space. At some point, he started calling it the “the troll cave” or “the ogre’s bridge.” He would actually page employees to his desk using this moniker. Our retail location has wonderful quirkiness (and a hardware store/lumberyard at that) to support such a good sense of humor.

Much to my surprise, and sense of loss to many, he gave his notice as he was going to relocate to be with family out of state. Well, despite the feeling of loss, the time to make use of my prior endeavors in theatrical design. It was time to make a troll cave.

Step 1: Getting Ready


Burlap material- enough for your set location


Spray foam

Spray paints, flat green, brown, black, white

± ¼ pint each of flat black and white

Dixie cup to make some grey paint

Smaller pieces of cardboard, newspaper, or paper bags

Gaffers tape

Miscellaneous screws

1/8” plywood door skin. A piece 3' x 7' fit my set design

Cabinet screws (I had washer head 1" screws)

Scrap lath for screws on backside of archway

Scrap 2x6 lumber

Weights (two at about 5# each)

Joint compound, about one quart

Other scenic design elements as discussed below

One boss with a very good sense of humor


Tape Measure

Drill/screw gun and screwdriver

Ability to rip the door skin to size (table saw, etc., or have the lumberyard do it for you)

Jigsaw to cut a half round


Staple gun and staples


A bit of a streak of madness

Step 2: Conceptual Design

Knowing the space, I had a general idea of the look I was after and how I was going to do it. Not being the best at planning, I took rough measurements, but didn't do anything beyond basic conceptual design. This had it's pluses and minuses. While I came back to measure more than once, it helped me work out some of the bugs. I also took pictures and video from the beginning so I could review (without being on-site and looking suspicious) the visual dimensions and where I might hang or install things. Had I to do it again, I would have taken about five times as many surveillance photos and videos, paying particular attention to place to hang things.

Step 3: Creating Forests

One of the elements will be burlap drapery that will give the idea of vine-y, forrest-y area and feel of concealment of a troll cave/ogre’s bridge. We're going to cover key areas of this office area to achieve this effect.

Make sure you use untreated or natural burlap. There are other products out there (that I almost used) that will smell from the preservative used on them.

Cut the burlap to size for the various areas you're going to place it. Cutting jagged triangles on the ends helps give the impression of hanging vegetation.Take your pieces and spray random, broken lines vertically with green and brown spray paint. The burlap gives an earthy, organic feel while the greens and browns help define a look forest vegetation.

One one piece, perhaps out of public view (for PC reasons, and to keep it an inside joke too) you might spray in black “Beware of Ogre's and Troll's”

Step 4: Expanding Foam Rocks

This was tricky. I used black landscaping foam for rocks so I didn't have to paint them. Do this on a plastic drop cloth as the foam will stick to anything. Wear gloves too, as it will take about a week for it to wear off your hands.

Ball up some newspaper or something into an organic form, tape where needed, and cover in foam. (Note: Because of how the foam dries, you can pick up a dried rock, but the bottom edges where it sat on the drop cloth will still be tacky. At this point, just leave it upside down for a while.)

The trouble was, because of the tubular nature of the foam when dispensed, the dried product looked like a pile of poo poo from a really huge animal. This was not the effect I wanted. Fortunately once dry, this stuff can be cut, which gave it a porous look, like lava or something. So I made random cuts to get an organically shaped surface. On the last rock, I disturbed the foam right after spraying it, and this had interesting, less objectionable, results.

Step 5: Building a Bridge, Part One

The bridge is going to be an assemble-on-site, so all the construction had to be made in pieces. My bridge was going to be 4 feet wide by 5 feet tall to match the opening in his area where he looks out on the store. The bridge will be eight inch wide pillars on each side and an archway at top. The top piece has an archway cut into it such that it is one foot tall at the top and curves down to two feet at the sides.

Have your lumberyard rip the door skin to size, or do it yourself. You will likely have to cut the curve of the archway yourself, or make some other design. Once cut, spray paint everything white. Assemble the arch and the legs, screwing the layers of doorskin together and into the scrap pieces of lath on the back side, making sure to get it all square. The self tapping cabinet screws I was using went in like a breeze with my screw gun.

Somewhat arbitrarily, I decided to have my top piece attach from behind the uprights. In any event, you'll want to draw a couple of pencil lines where things overlap to define what surfaces will and will not be seen. I then took it all apart to make things easier for our next step.

Step 6: Bridge Part Two, or Fun With Stonework

Take out your joint compound and spread it randomly over the bridge uprights and archway. I used a wide piece of hardboard to get a mass of joint compound onto the surfaces of the arch. I then paddled it from random angles to give it texture. The idea is that you're going for a rough, irregular surface to approximate a rough hewn marble surface. Remember that you're going to reassemble all of this, so don't cover the seams with joint compoundwhere the columns and the arch will meet. This is an important reason why we primed everything white in the first place and in the last step drew some pencil lines where the arch and leg pieces overlap.

Step 7: More Fun With Stonework

Once the joint compound is dry get out your black and grey paint. (Again, I already had some white, so I didn't get any grey, but made my own instead)

Your mission is to paint hints of organic shapes of grey over the white joint compound to introduce “veining” into the marble, and then vein the grey and white areas with black, darker shades of grey, etc. You're creating rough hewn marble with natural color variations. You could also use the black to define the borders of blocks that make up this structure.

If you wanted to be really crazy, you could take some green and make some moss, ferns, etc growing in certain places. Were I to do it again, I would have spray painted the marble effect on the backside of the piece so he would have something to look at while at his desk. I wouldn't try to use joint compound on both sides; something tells me it would get too heavy and more prone to crumble.

Step 8: Load-In Plan

Because I will be quietly doing this after hours, I have a little over an hour while people are working the closing shift before they'll be locking up for the night. Fortunately this “under the stairs office” is out of the way, so my coworkers will likely not know what I am doing. Planning is key.

So the checklist of stuff to bring from home:


Each of the burlap drops, rolled up and labeled

The bridge, in sections, with screws

Foam rocks

Other props (Snake to hang at manager level, butterflies to hang on a burlap drop, mini plastic trees for the keyboard, red light to backlight rocks)



Staple gun and staples

Gaffers tape

Knife and scissors

Red party lights for atmospherics (borrowed from the lightbulb section).

In my dreams, dry ice

Half dozen apple fritters from the Donut Station in Capitola (his favorite)

Prayers that the higher ups don't say take it down.

Step 9: Actual Load-In

I had my stuff boxed up and snuck it in the back through the lumberyard prior to close. Once the store was closed, it was go-time. I started with the burlap draping. I gaff taped the burlap that was installed at eye level locations or draped it over shelves where available, but allowed myself to use a staple gun in a few non-visible locations.

The install for the bridge was location specific, so it was seat of the pants. However what paid off was that I studied the location several times (I saw what computer cables needed to be gently moved, how certain aspects would present challenges in the install, etc.) I got it assembled, and then got it up with the help of a coworker, and we tied it off from above to hold it straight up.

Draping random pieces of long twine from the archway gave a good roots/vines effect, and hid the fact that one of those pieces of twine was actually helping to hold it straight up. Were I to do it again, I would have used some burlap to cover gap between the outer edges of the bridge columns and wrap around the permanent posts of the stairs, again, going for a draping look of forest and vines.

I finished off by hanging the snakes and butterflies, and placing the rocks with the red light for backlighting. I also bought a fake torch (the kind with a flashlight bulb and a fan to blow a piece of orange fabric in a random pattern) to put in the cave.

Step 10: Reception

My boss was blown away. I didn't get in the following day before he did, but he couldn't believe it. He let it stay up for almost three days before disassembling it, feeling like there was pressure from the higher ups to take it down. It was short lived, but fun as heck to make, even if I spent way too much money. It was proof that I could pull off theatrical set type of work and quite gratifying.

Thanks to:

The Instructable community for championing creativity and ingenuity.

The GC gals for a good burlap recomendation.

The yardies for cutting my stuff.

The very few that I shared it with for keeping it under wraps.

Kelly Tighe for teaching me in High School all the concepts I used here.

Donut Station for the best fritters and donuts I've found (I do it in moderation, honestly).

Howdy for being a, decidedly fair, yet awesome assistant manager.