View Full Version : Building a Cave

03-13-2007, 02:55 PM
We are planning on builiding a cave in our haunt and I was wondering what everyone would recommend. Concrete? Monster Mud? Spray foam? Has anyone used different materials and prefer one over another? Oh, yeah I want cheap also. We went on the Frozen Tundra Tour and we loved the cave at Terror on the Fox. That cave looked like some kind of spray foam.

03-13-2007, 03:11 PM
We are making a mine shaft for our trail, we are using the frame from a car canopy and covering it with vacufoam panels called cave wall. I will get the link from my brother and post it. The panels are 4x8 and can be rolled up for shipping ups or fedex. To save on the cost some of the walls will be covered with wet moss and parts that can not be seen will not have it on it. I'm thinking to do a 10'x20' mine shaft I will use 8 panels so that they will see rock here and there.

03-13-2007, 03:36 PM
wood cutouts, chicken wire, burlap soaked in plaster over it, use thin strips in between joints so you can sectionalize it if portable.

03-13-2007, 04:42 PM
I'm not sure if this would work? or be safe..
I'd like to 'bury 3-4 60' foot steel containers about 4 feet under grade,
with 4 feet of dirt on top,for a cave.
If it didn't collapse.sure would make a good storge place too..
I may be way off with this..ideal" don't want to hurt anyone..

03-13-2007, 04:44 PM
Well as far as the Terror on the Fox cave, I talked to Tattoo about it recently, and came up with about $8,000 to $10,000 worth of supplies to get that room like it was. They used spray foam from www.tigerfoam.com

They sell a kit that costs about $600, and can cover something like 100 sq.ft.

03-13-2007, 05:16 PM
I went and checked out the darkness on my way to transworld this year and Larry has a pretty phenomenal looking cave/waterfall room. I think it was carved out of styrofoam and plastic coated but you would have to ask him to be sure.

Jim Warfield
03-13-2007, 07:15 PM
The only cheap way to create a cave is to use a shovel and every back muscle you own.
I had a 1963 homemade horse trailer delivered to my backyard for $60.00. (4 horse model, I think?)
I cut off the axles , spun it around, cut out the nose-end, re-attached the axles where they now needed to be to wheel it over the chasm, buried some solid concrete blocks , welded legs ontop of the blocks to level the trailer up.
This could have been a cave, a tunnel, but it's my tomb. I laid up 150 year-old soft bricks at the entrance, made an arched doorway. Made a heavy steel door from a huge old electrical box my electrician neighbor threw away. The vines cover the sides of the horse trailer in the summer and fall, hiding it's lowly architectural pedigree.
$60.00, "Delivered!"

Greg Chrise
03-13-2007, 07:51 PM
We built a very long and tall cave outdoors from rebar with hardware cloth over it, then sprayed my secret additive in concrete and sand over that about 3/8 inch think inside and out. Total cost $1800. Caves to go?

It was intentionally half the cost of foam, and a third the cost of gunite. It ends up painted any decor. We have had one outdoors in tornado alley since 1998. The insulating quality of our formula feels like a real insulated underground cave and works well for haunts as this offers that other worldly different than everyday feel to a room or outdoor event.

But, it is secret technology only I know. Well, I did teach one other place how to do this and they have made cool volcanos and giant skulls the same way. Other than them it is a secret.

You must first know how long this thing is to last, wether it will be inside or out, if it must cone in sections or weighing 20,000 pounds is okay. It could be done over wood and very fine screen (harware cloth metal) stapled to it but the outdoor ones should be all welded together with a 12 inch rebar grid.

This same formula can have burlap dipped in it but, I would fire retard the burlap first if it is indoors The concrete and additive or monster mud doesn't burn but when subjected to a hot flame, these compounds crack and pop off and the burlap smolders for ever without fire retardant.

03-14-2007, 05:05 AM
Welcome to Jeopardy!
Alex' please: That would be " Ferrocement" for 100 dollars
try googleing it ,it's a very old cement mix..

Matt Marich
03-14-2007, 06:31 AM
Here's a link to classes and information on ferrocement. Larry, I would like to write on article for HW about a fast technique we developed utilizing spray foam. Would you and your readers be interested?


Jim Warfield
03-14-2007, 06:41 AM
Different parts of this country see very different kinds and durations of weather.
Here we might see below zero for a week or two , spring and summer can be very wet and humid. Mold loves the Miss. River valley!
All things to keep in mind when planning to build, especially if it is supposed to last awhile outdoors.
The corn likes the weather here.

03-14-2007, 07:01 AM
I would be interested in a How To on the foam. My haunt I will be building for 08 Will be underground theme. So My whole haunt is going to be a cave.

Dennis Moyer

03-14-2007, 02:53 PM
I attended the JPJ Synthetic rock construction class several years ago in Arizona. It taught me a lot about concrete and cement. Immediately after I built a huge "spider cave" and 60 tunnel (you can see these in the latest HW video).

If you have a permanent location and want to make something permanent, this this is a cheap and realistic way to go.

Since then I have learned a thousand ways to use plaster and foam, so I probably wouldn't build it the same way today.

Dwayne Sanburn
13th Gate

Raycliff Manor
03-14-2007, 04:21 PM
Matt, we'd definitely love to see the article!


03-14-2007, 05:45 PM
Arrrg, having flashbacks of a paper-mache cave I built about 6 years ago.

Worst idea ever!

And Matt, bring on the info, sounds great!

Greg Chrise
03-14-2007, 07:53 PM
This Ferro Cement method ends up having to be thick to suport it's own weight. With various acrylic resin admixtures it can be as thin as 3/8 inch and be very strong thus potentially portable. Chickens might peck through it over time but far less material is required. It is like "hardcoating the wire mesh rather than building up some thickness in several layers of chicken wire.

You could take some animal dung and straw too but that ends up being thick. What's that smell? There's Methane in that there mine! Why use cubic tons of material when you don't have too. What would Al Gore say?

03-15-2007, 07:13 AM
Here is a picture of our Caverns (9 feet wide, 9 feet tall, and 70 feet long), this is the area after Hell (our Main Cave) It is framed wth scrap lumber and wire mesh and sprayed with Tiger Foam. (Tiger Foam comes fire rated) The great thing is you don't need to paint it, you can light it to make the textures stand out. We found this out after painting ours (we paint everything under scene light) I will try to post more pics of the Main Cave and the Catacombs soon.


Take care,


03-15-2007, 03:11 PM
Thats awsome Tattoo, looks real to me.

03-15-2007, 03:25 PM
That cave is great.... What color is the foam before you painted it?

damon carson
03-15-2007, 04:09 PM
That cave looks really cool! Man fogged out and with some cool lighting and sound effects it probably really freaks people out!

Jim Warfield
03-15-2007, 04:30 PM
Making it look so really cave-like could open up some great opportunitys to create hiding places in the cave walls.
People's minds would see a round boulder here and there and make it have a round far side in their minds of it as nature makes them, then the far side could be flat, or hollow, creating a good hiding place right there in the wall, very unexpected.

03-15-2007, 04:45 PM
It dries to between a tan and yellow color, kind of like expando foam.

Jim, that is exactly what we do in our cave areas and there are several great hiding spots in the one picture I have posted. I will post more soon.

Take care,


03-15-2007, 05:25 PM
Do you use the slow rise or regular stuff from tiger? Thanks!

03-15-2007, 06:31 PM
We use the following:

Tiger Foam 600 bd. ft. Kit - FR
ASTM E-84 Fire Rated Foam Kit. All kits are complete with hose and gun and extra nozzle tips. This kit yields 600 board feet (square foot at 1") or 50 cu. ft.
Price $640.00

FR = Fire Rated

This foam sets up VERY FAST! Within a couple of minutes, if you use this product make sure your path is planned out so you can keep spraying very smoothly.

Take care,


03-15-2007, 06:33 PM
Thanks for all the detail it will def help!

03-15-2007, 06:36 PM
It will also get VERY WARM in the areas you are working because of the chemical reaction of the foam setting up. Read the directions VERY CAREFULLY!

Take care,


03-15-2007, 07:29 PM
De careful when using expanding foam. It releases vapors that are potentially hazardous.

03-15-2007, 07:33 PM
Just as reference I believe others have used Burlap soaked in Hydrocal... probably a lot more heavier then the foam but perhaps easier to create then using cement or other rock like material...

RJ Productions
03-15-2007, 09:34 PM
Thanks alot for posting that picture Tatoo. Just rub it in that some of us didn't get to go on tour and see your attraction!!! LOL!!!

All kidding aside your stuff looks great. I like the lighting you guys utilize. Maybe an article in Hauntworld on haunt lights or haunt photography, you seem to do both well.

Man, now I have to plan a whole trip to Greenbay...it would have been cheaper to do the tour for $177.00 !!!!!!

03-15-2007, 09:57 PM
We built our cave out of foam. But we hired a local foam insulation company to come in and do it. It was cheaper and the guy who did it for us was having so much fun that he did a bunch of extra stuff for free. Only thing we found out the hard way was that when you use that much foam it floats and we are close to the river! Had to put some cement in to tie it down to in the spring.

08-09-2007, 09:21 PM
we just tried making a cave themed area out of wire mesh and burlap covered with monster mud and it turned out pretty well,it wasnt as strong as i would have liked it to be but all and all looks pretty nice.

Chambers of Horror
01-30-2008, 04:56 PM
Matt, I'd love to read that article. I am a home haunter going pro for the first year (2008). I did a short cave entrance last year for my home haunt out of carved foam boards coated and painted. I am looking to do an entire cave maze this year and would love any tips and info you can give.



01-30-2008, 10:44 PM
Instead of using monster mud, use cement or concrete with a sand aggregate. Much stronger.

Greg Chrise
01-31-2008, 01:41 AM
Instead of using monster mud, use cement or concrete with a sand aggregate. Much stronger.

That's what I'm talkin about. Screw Monster Mud!

01-31-2008, 11:35 AM
Screw Monster mud?!? Ewwww! That sounds so kinky and messy. But you're right. Even regular plaster is better than Monster muck. And if you use fiberglass matte cloth with cement or plaster it makes an even stronger material.

01-31-2008, 06:09 PM
How would be the fire rating to use fiberglass cloth for a cave?

Greg Chrise
01-31-2008, 06:30 PM
Generally our caves are cement formulas in either an aliphatic or acrylic resin, spray tectured onto a mesh and rebar frame.

I experimented with taking low grade burlap and coating it like monster mud might be done then hold a torch to it.

The cement and acrylic depending on how thick acts as a natural insulator. It doesn not catch fire but with tremendous continued heat the burlap, untreated would begin to smolder. The solution would be to first dunk the burlap in fire retardant.

In the case of fiberglass cloth, I doubt it would obsorb fire retardent and it would melt. But, the actual test is an open flame for 30 seconds and just having the cement certainly does that. My tests were what happens next to a plumbers torch for a good 10 minutes.

High heat will pop anything realtive to moisture content and heat absorbtion. The ultimate instalation would have a fire retardant in the final sealer on the top coat of the concrete. How it works it as it is heated it is releasing chemicals for some time dispersing any open flame. The result would not be a penetrating heat such as a torch unless you were hit with a fire bomb.

01-31-2008, 07:57 PM
Many of the artificial rocks at theme parks and zoos are made from cement/fiberglass/rebar cast from flexible urethane or latex molds taken from real rocks. The molds are powdered with a cement release agent, then a surface coat of cement is sprayed in, followed by layers of fiberglass/cement layups with the rebar set into place. Several different molds are used to keep a natural look. The forms are pieced together like a jigsaw puzzle, welded together, then seamed with cement. When assembled, and the seaming is cured, the rocks are pressure washed to remove the release agent, then painted. A great book to get is "Artificial Rock Waterfalls - Rock Making Techniques For the Professional and the Hobbyist". It is available at http://www.rockandwater.com . They also have a how-to DVD and materials for rock making.

Greg Chrise
01-31-2008, 10:06 PM
Now is this mixed in strands or an actual layer of matting? Strand is no big deal and nearly doubles the strenght but generally would require a final skim coat to hide the strands in the structure.

01-31-2008, 10:19 PM
I rip the matte cloth into 3 to 4 inch pieces and dip them into some fresh mixed cement. I then place them onto the back of the surface layer and press into place, rubbing to smooth out. Also at this layup stage, I like to mix some Acryl 60 into the water for the cement. Makes a stronger bond.

Greg Chrise
01-31-2008, 10:42 PM
I might have to try this as a sample. I have fiberglass and even refined concrete products and mainly use the Acrylic additives but never put the peanut butter in the chocolate.

This expense wise sounds like THE thing. Burlap is too grainy and nasty, steel mesh is very expensive. Fiberglass mat might be just right.

01-26-2010, 09:48 PM
Here is a pic of my cave it was done with spray foam.