High and dry

Masonry arches for making roofs
Covered with timbers again and again
Proving again these basic truths
Stone stops fire, wood stops rain.

A masonry arch alone is strong
For centuries it’s not weak
Stone alone will last so long
But is all too prone to leak.

Cathedrals and churches use a roof
both inside arches made of stone
and outside wood and waterproof
Stone stops fire, dry as bone.

This old tested proven approach
Still works well, still today
Another topic for us to broach
Of thermal mass and its way

To keep a building truly warm
Helps if there is radiant heat
Stored in rock or stony form
For this to work, is a feat

Insulating the outside’s needed
For allowing radiant heat to pass
To the inside unimpeded
Bare stone inside: thermal mass.