I'm really surprised by the power of the blast.

I'm guessing you've probably never seen a grain elevator explode in person. I have (although it was a looooooong time ago).

Anyway, the difference between a fuel air explosion (deflagration) and a detonation is that a detonation produces an omnidirectional overpressure wave. A confined gas explosion in a house won't. It is creating pressure; it will push on the walls and ceiling but as soon as the pressure finds an outlet (usually by ripping the roof off the walls) the acceleration stops. In this way the house is behaving more like the cylinder of an engine and the roof is acting like a piston.

This is why a bomb in a house tends to leave a crater (or at least, a cleared area surrounded by debris) where a fuel explosion tends to leave a big pile that's fallen in on itself. A very, very small bomb might produce the same effects, but it won't flare up as soon as it gets more oxygen.

I'm really surprised by the power of the blast.

I'm guessing you've probably never seen a grain elevator explode in person. I have (although it was a looooooong time ago).

Anyway, the difference between a fuel air explosion (deflagration) and a detonation is that a detonation produces an omnidirectional overpressure wave. A confined gas explosion in a house won't. It is creating pressure; it will push on the walls and ceiling but as soon as the pressure finds an outlet (usually by ripping the roof off the walls) the acceleration stops. In this way the house is behaving more like the cylinder of an engine and the roof is acting like a piston.

This is why a bomb in a house tends to leave a crater (or at least, a cleared area surrounded by debris) where a fuel explosion tends to leave a big pile that's fallen in on itself.