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Foundation Help: Wood Pilings vs Cinder Block

Posted by suzeec (My Page) on
Sun, May 24, 09 at 11:17

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.

Suzan


Follow-Up Postings:

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RE: Foundation Help: Wood Pilings vs Cinder Block

There is a FEMA document that they issued after Katrina to simplify foundations. I think it was FEMA55, which was the short version, and FEMA550 was the long version. I did a quick search on www.fema.gov, and that appears to be the right number (just type in 55 or 550). I'm not sure what bell bottom pier construction is, so can't help you there.

My impression is that wooden pilings fared better than cinderblock or concrete pilings in Katrina. My theory is that the connections at the ends were better. We saw many cases where the concrete or cinderblock pilings were fine, but the house had floated off. And at the top of each piling was an itty-bitty piece of plate. At most, 4"x1/4". But, there are good brackets available, so what your engineer said about cinderbolck and concrete being stronger than wood if done properly is probably true.

Here is a link that might be useful: FEMA document search


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RE: Foundation Help: Wood Pilings vs Cinder Block

carterinms, I must thank you again. I remember now seeing something on the FEMA website right afte Ike and we were doing all of our mitigation research. So many websites I have visted for sure.

Many of the homes destroyed during Ike were older and in High Velocity zones and from what I hear it didn't matter what type foundation they had, becuase the surge was just so high and the debris field was so broad, that they didn't stand a chance. The ones that were left standing, whether wood or concrete, were the new construction that were at 18'-20' elevation above grade. We aren't high velocity, although after Ike, I don't think I can ever be too sure what may happen. We are a 1/4 mile from the bay and never dreamed we'd get that much water up here!

Have you all gotten to move in yet? I hope so, it certainly was a long time coming. We haven't broke ground yet, but we are closer. Many of our neghbors are back in their homes, so the neighborhood appears to be coming back, which is a blessing. Anyway, I do thank you again. Would you mind posting the link to the journal on your build? I thought I had it in my favorites, but I don't and I can't find my other post.

Best Wishes!


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RE: Foundation Help: Wood Pilings vs Cinder Block

We are in our third week of 4 weeks to go! DH has been working on the staircase - it's gorgeous but has taken a lot of work. I need to update the blog with some new pictures. Maybe tonight.

He still has to finish the porches (2.5 days), sand and finish the floors (1 week?), build and install kitchen cabinets (3 weeks), and finish installing the lights, ceiling fans, appliances, kitchen faucets, etc. (1 week). Then we'll see if the county is going to be a pain about letting us move back in.

Here is a link that might be useful: Bayou Build Blog


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