Roof Load Zone Map

[JD]

This post is a continuation from a post in the Repair Forum from Dean3.

I believe the current HUD roof load map was established in 1974 but the map was based on the existing CFR (Code of Federal Regulations). I guess the CFR regulations were difficult to discern because of many revisions and ammendments. The HUD roof load zone map was produced because of this confusion but did not change the map that CFR already used.

Also in 1994, further definitions and codes were produced with BOCA and Miami-Dade requirements. And as always, local jurisdictions were able to increase the requirements (with approval) set by HUD for factors pertaining to their local area.

For a sleepy read, this information can be found at http://www.tiedown.com/pdf/d3280.pdf

What I find interesting is the South Zone. I am in the same zone as nwwoman with the snow problems and my daughters that have seen up to 2 feet of snow this year. The heaviest thing to land on roofs in my area (short of ponding water) are repair guys and big birds.



JD

[Dean3]

On the map on My data plate(actually its a sheet of paper)it shows the northern zones similar,but not the same. The one You posted is roof load tho and I think the one in My furnace closet shows more generalized "North" "Middle" and "Hurricane" zones. It mentions both wind and snow "live load".

It is marked Ansi A58.1 - 1972 although My home is a 1976. The lower left corner of the plate is missing,that lower left is one place the zone names should be so some deciphering is needed to determine the snow load ratings per zone.

This site mentions My map for wind;

http://www.gostructural.com/article.asp?id=1401

I haven't found a duplicate map image on the net,most of the PDFs and such are wind related and/or don't show the map,at least I haven't found one for free.

Looks to be that both nwwoman and I are close to the Middle zone on Your map,on My map it is called "North" and I'm in it(near MN)but not by much. On My map the eastern 1/3 of Washington State is in the North zone.

I'll guess it is the Pacific winds that keep most of Washington State classified as Southern.In that respect maybe My map is shaded a bit more acurately,I would think that farther inland the Canadian cold would drop down and influence the eastern end of Washinton,,just a guess tho.

As to North Dakota(not to mention SD)being in the South zone HUH?!?! Its gotta be colder than He** and snowy! Maybe they count on high wind to blow the snow off of roofs?!?! I'm mystified. ND isn't shown in the North zone on My map either,,kinda hinky I think,,I've never been there but do believe they get lots of snow.

Wait a minute,,could the mountains explain the western black-shaded Middle zone and lake effects explain the other 2 black ones? Do lake effects back up against prevailing winds to explain MN? LOL! I'm missing something or these maps We have raise more questions than answers. Ahhh well,its fun and educational.

Dean

After perusal of My post I deem it "sendworthy",by My messed-up standards that is!(hmm looks like a good signature for me)

[nwwoman]

Nice map. From what I heard on the news, we needed to have 40PSF to deal with the snow here in SE Washington. I'm 6 miles from Idaho and about 50 miles or so north of Oregon...so right on the area where the three states converge, although I'm on a plateau at about 2000 feet above sea level. Many roofs in this region have collapsed... Wal Marts, schools, grocery stores, a church, awnings and more. I've lived here for a long time and never seen anything like it!

[JD]

My home state is Washington. From the Seattle area though. But when I was a pole barn builder, we went to Yakima, Mason, and other places I don't remember now often. Yes, difference of night and day between Eastern and Western Washington, both winter and summer. I would think the 40# roof load would be what's needed in Eastern WA. But my daughters are in Western WA and they got the 2' of snow. I have seen many 20# (1x2 trusses) roofs in that area. Can't imagine that that is enough.

JD

[Greg]

I think the "Load Zone " map is due for an update. Syracuse NY, the snowiest city in the country is in the same zone as Miami. Must be a Government map!! Greg

[Dean3]

Too true Greg. Maybe there should be a line on the old Mason Dixon straight across to the western slopes of the Sierra Nevadas,then north. Naaaa,never work would it?!

I just did some snow load googling,the pdf files seem to say it is a very local thing. Looks to Me it would be costly,to say the least,to make an acurate national map. I would guess it should be interactive,like google earth,just pan/zoom for local details.

I did see some advice on a forum result that sounded good, "for Your area results,go to local Government to get live/dead load info",not an exact quote but close enough.

Do We engineer to budget or engineer for safety? Looks like "a rock and a hard place" to Me. When You build a super strong roof then You might as well continue down the walls and keep building strong to the base.Ummmm,not in that order usually!

Dean

[nwwoman]

A friend with a double-wide on 10 acres in panhandle Idaho..just outside Moscow, Idaho...experienced beam failure, ceiling collapse during the snow of last week. Contractor told him that snow load requirement for his place is 60 psf???? They are trying to determine if his walls will support that type of a new roof...otherwise house will be declared a loss.

60??