What is the frost line depth?


Old 06-20-03, 11:04 PM
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Question What is the frost line depth?

I was wondering if there's such a thing as a map, book or any publication that shows how deep the frost line is in various parts of the country. I posted this question to usenet not too long ago, but nobody seemed to know. I did a Yahoo search and, even though I found quite a bit of "bury it below the frost line" type of advice, I still couldn't find any information on the frost line depth itself. Considering how important this is, I find it hard to believe that nobody has ever published anything on this subject. Does anybody here know where I can find such a thing if it exist?

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Old 06-20-03, 11:43 PM
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Well I found a link to a publication on First Gov. web site.


go to page 167 of 483 pages, this is a large file, if you are on dial up it could take awhile. This link will take you straight to the file. There is a map in there but it is hard to read.

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Old 06-22-03, 12:18 AM
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Thanks for the URL. Even though I've found Air-Freezing Indexes before, I never knew that there was a table that I could use to translate the AFI into frost line depth information with.

I did manage to find a clearer AFI map for anyone else who might be interested: http://www.ncdc.noaa.gov/img/fpsf/airfreezeusa_lg.gif

I also found AFI stats listed by city: http://www4.ncdc.noaa.gov/ol/9712/AFI-pubreturn.pdf

This makes me wonder why 18" is code in Chattanooga, TN. After all, according to the list, there is no frost line worth mentioning in this city. I guess 18" is the minimum allowable depth no matter where you go even though some people are obviously known to bend the rules a little. After all, my existing water line is only buried about 8" deep.

Old 06-22-03, 12:27 AM
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The fastest source of "frost line depth" should be the local Building Inspection Department.
Obviously it is different everywhere, such as the difference between Phoenix and Philadelphia.
I'm in Eastern NC and I think that it's 18" here too, but I have no clue why. It probably hasn't frozen that deep where I live since the Ice Age. LOL
Old 06-22-03, 05:20 AM
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Many codes have the minimum burial at 12" BELOW the frost line for your area.
18" would have a 6" frost line. Not very cold where you live.
Where I'm at 42" is really common, but I seen 36".
One of the worst days of my life involved a backhoe with an ice tooth, 48" depth of frozen street, and a 8" water line. Cast Iron feels like frozen dirt....
Old 10-30-09, 11:35 AM
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frostline depth in fort worth texas

does anyone know what the frostline depth is in Fort Worth Texas?
Old 10-30-09, 11:54 AM
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RCB..there are general charts..but a quick call to your local building department might be quicker and more accurate. We have some guys here from that area..but no telling when they might be around to answer.
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