Here I'll show you how to make a fake rock cave/basking spot for your reptile cage. This is one I've made for my Bearded Dragon, Viggo.
Step 1: Design!
This is my original design I made months ago. The design has changed since then, but this illustrates the basic concept of what I wanted to make. A large cave, with a door allowing access to it from the outside, a basking spot above, and a ramp going up. PLAN AHEAD. I can't stress this enough. It will make things much easier for you. I've used Google SketchUp to render this 3-D model. Google SketchUp is a great FREE architectural 3-D design program. I'd consider this (or a similar program which may not be free) to be an essential tool for any craftsman/designer/builder. You can download the program here,
Google SketchUp Download
Step 2: Gather Materials and Tools.
Styrofoam ~ Free (This is trash, you can find it for free. It's used to pack all sorts of things. Try going to the back of an electronics store and asking if they've got any you can save from the landfills. I used a broken styrofoam cooler and some odd packing bits.)
Grout mix ~ $8.98 (I got a carton of Sanded grout mix in HEMP color. The sanded leaves a rougher texture than unsanded. The hemp is a kinda dark gray color that already looks like rock. It gives a nice dark base color and could be used without coloration if you want)
Cement Color ~ $4.96 (I used Terra Cotta. Mixed with the Hemp grout it gave a nice red rock color. This is a liquid color mix. You can also use powdered grout color mix. It's about a buck cheaper, but they were out of the color I wanted.)
Great Stuff Expanding Foam Insulator ~ $5.00 (Trust me, this stuff will make things much easier and is well worth it)
Water ~ (To mix the grout)
Water Based Polycrylic Satin Sealer (Go for Satin, not as shiny as gloss and gives a more natural look. You'll need enough for 3 coats. A small can will probably suffice. )
Knives and hand saws (to cut styrofoam and shape your cave)
Hot Glue Gun and glue sticks (works great for gluing pieces together and it's safe. DO NOT USE SUPERGLUE. Superglue, or other such chemical glues will melt/eat through styrofoam and give of toxic fumes)
Bucket (For mixing grout in)
2 Cheap Bristle Paint brushes (One for applying grout, one for sealer)
Step 3: Start Building!
The best advice I can give you here is to actually work inside your viv. This helps you make sure it will fit, as well as gives you an idea of proportions. You wouldn't want to accidentally make it too large. Remember to leave some extra room around the edges. You don't want it to be a tight fit now because you still have to grout it.
Start with a real rough cut, just laying things out. Don't glue anything down yet. It also helps if you can draw on the floors and wall of the viv to give yourself reference points for shape. If you don't actually want to mark your floor, lay down some newspaper you can draw on)
Get your basic shape together. Don't worry about leaving holes and don't do any detail carving yet.
Step 4: Glue
In order to get everything back the way you have it now, it really helps if you draw marks and lines onto your shape. Trace the outline of a piece onto the piece below it. Trace the bottom footprint onto the bottom of your viv or newspaper. Take off each layer and start gluing things down working from the bottom up (don't glue it to the floor!)
Step 5: Expanding Foam!
This stuff is truly great. I guess that's why they call it "GREAT STUFF"
Spray it in to fill in all those little holes and gaps.
Use a little more in places you want it to build up.
Leave it to expand and dry overnight.
Step 6: CARVING!
Pull out your knife and saw and go to town! Time to get creative and let your artistic side show. What you're carving now will be the shape of the final piece. Remember, don't go into too fine detail. The layers of grout will fill in a lot of the small stuff completely. If you want it to show up, cut it deeper!
Step 7: Grout!
Ok now, time make this look like a rock, and not a big chunk of foam.
Mix your grout. Don't mix it all at once. Leftovers will dry out while you're waiting between coats. Try using about 1/4 of your grout per coat. I don't really have a set measurement for water, but you want it to be kinda thin and soupy. It will brush on easier that way. If you're using coloration, this would be the time to mix it in.
Once you've got your soupy grout, start brushing it on.
Make sure you get in all the cracks and crevasses, including the bottom.
Let it dry overnight between coats.
Apply 3 coats! This will ensure everything is covered and it will be nice and strong.
Step 8: Paint!
I didn't paint mine, just used the cement color, but if you're gonna do that, now would be the time. Acrylic works best I hear.
Step 9: Seal It.
This is a very important step. Use a safe, low fume sealer such as Water Based Polycrylic sealer if possible. Shellac also works well but will leave it shiny. I actually ran out of polycrylic so I used shellac inside the cave and on the bottom where it wouldn't be seen.
Use your other brush and apply 3 coats of sealant, once again, making sure to get into every crack and crevasse. Sorry, no pictures here, cause there's not much to see while sealing. Once you've finished, let it air out for a few days, preferably with a fan blowing on it.
Step 10: Enjoy!
Well, this step isn't so much for you as it is for your dragon, but hey, you can still sit back and enjoy looking at your handiwork.