I always found that the problem with Lego was that although amazing things could be built, they never fell down in a realistic manner.
With my brother we did the creative destruction using bangers, but this tended to be 1) very loud, 2) damaging to the lego and 3) bloody dangerous to life and limb of 10 year olds. Nevertheless, fireworks did prove an effective way to destroy traditional lego buildings (Video anyone?)
At playtimes, therefore, the object was to decide if either construction or wanton destruction was the object of the play and modulate the build technique accordingly.
Using common 4×2 lego bricks, it's possible to make constructions that behave in a far more dynamic fashion when blown up \ knocked down \ hit with toy cars. My problem as a kid was always that lego buildings were brill in every respect in every way except for those temporary constructions made only to be creativly destroyed. creative, realistic destruction and lego don't go together. Here is presented a breif ananlysis of other methods for building with lego to construct more deformable buildings.
Pretty effective technique for reducing lego buildings to constituent parts. Carries side effects such as extreme noise, bloody dangerous and tends to both leave scorch marks on the lego and break the parts into smaller pieces than intended. Much smaller. Many of what are now my sons lego blocks carry residual burn marks from my own experiments as a youngster.
Sideways block building
The technique is simply to ensure that the building rests together. make the walls by having the studs on the side. Looks best when the studs face outwards. Interlock the blocks like normal. Use short blocks. If you are patient, use 'thinnies' like 6×1 or 4×1. insert doorframes and windows in the correct orientation. use the long technics bars for joists. Be patient with this method and it will pay dividends.
Sideways block building has the potential to provide the most realistic results. It should be completely feasible to built 2 or 3 story buildings. Fully sloped roofs will be hard though. perhaps hybrid the technique with the playing card method.
At destruction time, you will like the results: those technics roof beams fall in a most realistic way.
In this Technique, use playing cards and 2 x 4 bricks on end to build large open structures which deform most marvelously. Use the blocks sparingly: spared them out at the corners so that one brick can support 4 card corners. Fill in the walls with upright blocks if necessary, but I find that huge carpark type building look great when open.
In the past, buildings of 20 floors with 6 packs of cards have been built and demolished.
Pretty much the same as playing card floors really, but use those AOL CD's instead. Pretty easy to build free standing structures as tall as a room: say 12 feet with no problem. Careful when it comes down: CDs falling from ceiling height can hurt a bit
Apart from the earlier mentioned method for desposing of standard lego structures, I generally find that the best way to 'blow 'em up' is to chuck 2×2 squares at them. these tend to cause just the right amount of damage without it taking too long.
More recently, I've been using a BB Gun equipped remote control tank. Marvellous!