Thanks Bill. I saw that study from CSU as well. Will attaching the beams to the posts be strong enough with just carriage bolts supporting all the weight? I would imagine the setting the beams on top of the posts and using a Strong-tie would be the way to go.
On 8/20/2011 8:28 PM, Bill Chmelik wrote:
-----Original Message-----
From: DoIt_Yourself@yahoogroups.com [mailto:DoIt_Yourself@yahoogroups.com]
On Behalf Of John S. Moss
Sent: Saturday, August 20, 2011 2:44 PM
To: DIY Group
Subject: [DIY] Deck Construction Questions
I'm building a free standing deck landing with stairs next to an existing
deck. It will be 4x4 on 4 6x6 PT posts with 2 2x beams.
1. I'm located in Denver. What's the frost line? I have seen anywhere from
24" to 40".
How deep is the frostline in the winter in various parts of Colorado?
A good question for which little quantitative data are available. It is a
function both of temperature (related in a general sense to elevation but
not strictly) and snow cover. Where snow accumulates deeply, little frost
penetration occurs. Here in Fort Collins where we measure soil temperatures,
there was one winter back around 1930 with extreme persisting cold and very
little snow when frost penetrated to more than 30 inches. In most years, the
max frost penetration on level, non-shaded ground is only 10-14" (much more
in shaded). The greatest penetration in the past 20 years has been 18" at
our site. We have had many mild winters recently, and we've had some with
only a few inches (3-8") penetration. The ground is most likely frozen from
just after Thanksgiving until sometime in early March at our station. This
year, the ground remained unfrozen all January except in the top 2 inches at
night and in the morning. This was very unusual.
A location known for deep frost penetration is the San Luis Valley since
they have little winter snow but prolonged cold temperatures. Penetrations
as great as 5-6 feet have been noted, although 3 feet is more common.
In snowier locations, frost penetration is not a big deal -- only a foot or
two -- except for where roads, driveways, sidewalks, etc are kept clear of
snow. There the frost penetration is much greater. We always recommend
contacting county building officials in each individual county, since they
are much more familiar based on regular contacts with experienced excavators
-- they don't have data, but they do have experience, and that has usually
been place into county building codes. -- Answered by Nolan Doesken
2. What size beam should I use? Is a double 2x12 overkill?
A four foot by four foot landing will be fine with 2x8's and for a four
foot spread they do not have to be doubled beams
3. Should I notch the posts to accept the beams or set the beams on top of
the posts?
You don't need to notch the posts, use 2 carriage bolts per connection
4. How far can I cantilever the deck past the posts/beams?
Cantilever is dependent on the spacing of the joists, the size of the joist
and the material the joist is made of, most codes allow between two and 3
feet on decks.
I've seen many different answers and am just trying to reach a consensus.
Any further info or links would be helpful and appreciated.
Thanks,
John
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