Foundation Help: Wood Pilings vs Cinder Block
I need help determining what type foundation will work for us, that will not sacrifice structural stability, but will still be cost efficient. I live in Southeast Tx, on the coast. We are in the flood plain, but not a high velocity zone. We have very heavy clay soil. We had soil samples taken and they suggested 10' bell bottom piers. The house will be elevated 8' above grade. The total sq ft including wrap around porch is 2800 sq ft. Our current design is spec-ed with 42" Bell Bottom Piers @ 10' deep and a 14"x24" Perimeter Beam. The columns are 16x16 CMU (Cinder Block). We will have 34 piers total. We chose the cinder blocks for 2 reasons, first being that we were getting the cinder block and re-bar dontated to us by a friend in the refractory business and second, when I discussed it with the engineer he said that structurally cinder block was stronger (when done correctly) than wood. He also said that poured concrete was the best option, but that is definitely out of our budget range.
The dilemma now begins, we started getting bids and most builders/contractors prefer wood pilings for cost reduction. I would like to be able to compare the 2 based on actual cost. We thought that getting the cinder block and re-bar free would reduce the cost of going this route, but that doesn't seem to be the case. The additional cost we will incur if we go with wood, is going back to the engineer and having them redesigned using wood pilings. My concern is that with wood, will we end up with more piers to drill? That would alter the way intended on using the lower level (as a garage and entertaining area).
I tried to get a number from the builders, like concrete cost per pier is 'x' as opposed to wood is 'x', but with wood we would need 42 instead of 34. Then we could make an informed decision. Make sense?
I also wondered if anyone has knowledge of the difference between wood pilings vs the bell bottom pier construction. My Dad just finished his build and he used wood pilings. He is in a high velocity zone. His pilings (24 of them) are 10'x10' @ 8' elevation above grade (not sure how deep they went), but there was no concrete poured around the base of the pilings. Is that typical? Does using the wood, aleviate the need for the bell bottom pier? I tried doing some research online and didn't have much luck. There was alot of information on the strength of the materials and their actual load capacity, but most of the info, was over my head!! Our engineer is out of the country right now and won't be back for a month (maybe longer) or I'd call him, but we have got to make a decision quickly, so we can get some good numbers for our budget.
Any assistance would be greatly appreciated.