That looks good. 100 hit points? Or is that too low?
No that's plenty. The statue is tireless remember, so it can repair a structure 24/7. It can just stick to the job until it's done.
A three-foot thick stone wall has 540 hit points (I don't think the rules say how wide the wall is, but I'm guessing that's for a single 5-foot section). Thus a half-destroyed wall would need ~270hp to repair and take the statue 2.7 hours to fix.
Over a day a statue can repair 2400 hit points of building, or 8.88 sections of 3-foot thick stonework - which should be enough to completely fix a half-destroyed 15-foot square solid stone shrine with a shattered door and ceiling. [nine 5-ft squares, seven of which are occupied with walls (7*270hp), one square with a stone door (60hp), plus a stone-slab roof over the central square (60hp) - total 2010hp to repair]
Looking at it like that it seems quite a lot, however it's only the equivalent of Fast Healing 1/6, so it isn't anything that is effective during combat-time.
Although that makes me think we should add a note that it only works on inanimate structures, and that the Statue can never repair Constructs or petrified creatures?
Actually, come to think of it I like the notion that they can repair other Statues That Work or similar stone golems. It would help explain why they're still around - one of the statues duties is to keep each other running.
Revising...
Repair Structure (Su): A statue that walks can magically maintain or rebuild a building or other structure, molding stone or wood as if they were putty (treat as the
stone shape or
wood shape spells). It can smooth damaged sections back to their original condition, or form raw materials into new parts for a structure that is partially destroyed. For every hour the statue spends repairing a structure it can repair X hit points of damage.
A statue that walks can use repair structure to heal the damage of another wooden or stone golem, including other statues that that walks. It can not heal any other kind of golem or living creatures that have been petrified, nor can it fix a wood or stone golem that has been destroyed.
