diaramas ruble

I'm in agreement with Muzzleflash, to a point. I use gravel and smash it with a hammer. Keep the dust from the gravel also, as it can be spread around the grounds and the buildings. You would want to use white glue to keep it in place.

Similar methods here on my end, I pour plaster (usually tinted with some different colours), smash it up, put it in ziploc bags, different bag for each colour to save for later.
I have a little tub of toothpicks that I've painted different colours and all snapped apart, along with bags of ballast and some bricks, brick coloured gravel from Michaels craft store (Xmas Village stuff)
I take all "ingredients", and mix them in a jar, and pour onto my base, then start adding bigger beams of balsa wood, shingles, etc. Once I'm happy, I glue the whole mess down with white glue/water, and add a wash once dry, some drybrushing and top off with weathering powders....a couple of examples...

Ha-ha, very good!!

Remarkable. I never though about that. I bought some nice bags of stuff at a model show. The guy was dumping them for a buck a bag and with the exess of stuff I had laft over from a Custom Dioramics kit I'm in fat city. I've got a ton of sticks I got from eating State Fair corn dogs. Square off the edges and they make beautiful timber. Popsicle sticks are kinda wide,but they work to. I shave them with a hobby knife to get long slives to simulate busted up wood to put in bombed out/destroyed buildings. Here's a trick for large piles of debris. Build a lump out of celluclay. I painted it grey with streaks of a brick color. Then i took my brick and stone rubble using white glue and liberally dropped the debris on it adding the broken timber slivers.

lay a shallow tin of plaster, let it dry, go outside and throw it on the ground, then paint as needed. for brick rubble bang up a brick

for concreat rubbel and stuff like that just take a chunk of concreat and do what Muzzleflash88 suggested

hahahahah i was going to suggest the same as muzzleflash.....
it's the only way .when you need red brick rubble...and if you need stone.a lump of sandstone given the same treatment will also get you the desired results....

get a no-bounce hammer,a shop towel or rag, a red brick,and a glass of ice tea.

go outside.
wrap the brick in the towel
beat the daylights out of the brick until you get the rubble consistency you wish :)

refresh with ice tea as needed.

(well that is what i did recently and I will post pics of the dio completed soon)

2 good woods for making bombed out buildings are basswood and balsa. Balsa might be cheaper but basswood is more stable. At least thats my opinion

Kitty litter makes great rubble, so does chunks of sheet rock (gyproc), bits and pieces of old bricks work too. Just about anything.