This is a multi-school, leveled skill. When a building is torn down by a player with this skill, a fraction of its construction materials will be recovered. Higher skill produces a larger fraction.
Note: Compounds produce no salvage. For buildings that require a Small Construction Site or Medium Construction Site to be built first, materials are not returned for the site itself.
Upon further review, third telling salvage rates do not seem to fit any nice function, as the classical diminishing returns to scale seem to stop, or at least pause. Maybe it's all a bunch of goofy rounding.
When a building is salvaged the above percentage of materials will be returned, with a random component of plus or minus one or two of each material.
This roughly translates to "get level 3 for 200 firebricks, 1000 cc and 100 candles". This will give you 75% rather cheaply. The remaining 4 levels are of much more debatable value. - Cappu
The biggest value, I would think, is in repeated building testing - mines for gem grids, quarries for random drops, Life towers for bonus veggies. A savvy player can almost undoubtedly recoup the cost of level 5 or 6 with a little bit of effort. --Sedelyan
remember you can't salvage aquaduct towers. - Menoblack
Tale 2 data is here.