Stilts or Slab, which costs more?

3 Replies

I have a property on lake Travis that I would like to build. The main obstacle is that the lot is  nearly 20' below the floodplain and would require some significant stilts. There are many houses built this way in the area, but do any of you here on BP have any experience with homes built on stilts; pros cons cost difference from a normal slab? The size of the home would only be around 1600 sq ft. and I am looking at going with a basic rectangular shape. Any one that has built one in the austin area, or anywhere for that matter? Any help/ advice/ tips would be much appreciated! 

We do a lot of work in flood zones and from what I've heard regarding "stilts"(we call them pilings) is you're looking at 20-30k extra over a traditional slab with a crawl space....Most of our footings are within a couple feet of sea level so we've never needed pilings but if you're indeed that deep you defintiely can't pour a footing on top of muck.....The other concern is flood insurance - the lower your first floor elevation the higher the flood insurance - I'd imagine if your first floor is under 10' the insurance would be astronomical.....your best bet is to talk to an engineer, get a survey, and go from there.

Definitely contact an engineering firm that has experience in deep and elevated foundation design; 20 feet below floodplain... that's rough.  

Do you know the exceedence interval that estimate is from (e.g. 100-Year Flood = 1% chance of water reaching that elevation in a given year)? FEMA requires infrastructure that provides a minimum risk reduction of 1%EI to even get flood insurance, and I doubt you'll find it economical to elevate above 20 ft, if that's what you need.

Good luck!


Hey Joseph and Joseph... thanks for the responses! The lakes "full" level is only 681' where the FEMA 100 year flood plain for the Lake Travis area is 722'MSL, and the property is at around 705' +/-. the circumstances would be a little different than coast front as it is not mucky soil as suggested. The property is level but fairly rocky soil as Lake Travis is mainly limestone based. Due to the difference in the "full" lake level, and the FEMA flood zone, building this high (or close) above floodplain is typical of lake front homes in the areas of Lago Vista as well as Graveyard Point as lake travis is part of the colorado river and not a constant level lake. Codes are for the living space to be at least 1' above the flood zone (so at oor above 723') which I believe would make flood insurance similar to any of the properties in the area that are out of the flood zone simply because the living space is above flood plain. I am probably best off meeting with a builder that builds flood plain homes in the area, but just wanted to get an idea of what to expect.

The responses are appreciated!-James

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