10-22-2013, 12:54 PM
quote:
Originally posted by ericlp
with the earthquakes we get around here ... I'm thinking wood will outperform steel. As wood will flex unlike steel. But what's just me. There is a lot info on the net. That's also a concern with cracking of slabs during a nice jolt.
Steel is strong and stretchy while concrete is weak (in tension) and stiff. Unless the steel is pre-stressed, cracking is normal and inevitable and the steel is there to hold the chunks together. This works well enough most of the time. In cases where a certain amount of cracking is unacceptable pre-stressing of the steel is done. Pre-stressed post-tensioned slabs are not uncommon in certain parts of the country where the soil expands and contracts a lot over the course of the season. I personally think that spending the money for the extra materials to make the slab strong enough to span any crack that forms underneath it is the way to go, plus put it on top of a double thick layer of crushed stone fill to isolate it from the ground. Make sure it is NOT keyed to the rock underneath. Now build whatever you want on top, pinned to the slab. The ground can move underneath it for all you care. The whole bit about houses on piers walking in a productive way has always struck me as deep rationalization.
Steel reinforcement of concrete is a mature technology. Ships have been made of the stuff that have lasted for decades. Those that last are very well built with extreme attention to steel placement and cover. I have never seen a house foundation built with that sort of attention to detail. I don't know the specifics of the Castleblock and similar systems but I bet that either the components are factory made with good quality control or for example in the case of ICFs the design of the block makes it very difficult for the builder to get the re-bar wrong.