This was a quickie job for a film that required a suburban house to blow up. A section of brick wall from the real house was photographed and a pattern repeated in Photoshop. Then, 8.5x14 inch sheets of bricks were  printed out on a standard Epson ink jet printer and spray-mounted in place. The tree out front wasn't an exact match since it was never seen in the connecting footage; only in the explosion shot.

This shot gives a better idea of scale. That's me prepping the model with a light drizzle of gasoline. A 4 inch mortar was positioned behind the balsa wood door of the model. The mortar was filled with compressed packets of gunpowder, sawdust soaked in gasoline and debris.

Yours truly.

Because the shot was filmed high speed, two charges were used. One for the blast that blows open the door and a second blast that launched debris trailing the fire ball. To achieve the split second delay for the secondary charge, a "relay-chain" was used. Essentially, it is a group of 10 double poled relays in a series with one relay activating the next relay, etc. By experimentation, it was determined which relay would give the right amount of delay for the second charge. The delay was totally repeatable, even though operating in time increments of a thousandth of a second or less.