Re: OT: Deck building

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Posted by Igore (71.32.191.180) on 08:36:37 07/16/08

In Reply to: OT: Deck building posted by Peter

I live in Minnesota and my subsoil is clay so there are lots of frost problems (6 to 8 feet down in bare ground). In our situation...

The concrete pillar with the post anchored to the top is very good design. The main thing is to include some rebar in the pillar. The concrete is usually poured in cardboard tubes. The tubes are fairly smooth on the outside and resist being lifted by the surrounding frost.

This foundation system was even stable enough to anchor my old large satellite dish on a 3 point mount where frost movement would be critical.

I've had good luck with fences with the following supports; I use a treated 4 x 4 set in a hole in the ground. I then back fill the hole around the post with dry quickcrete mix. A liberal application of water then sets the quickcrete in place overnight. This fills all the voids in the hole and prevents water from pooling in the clay like it would if I used crushed rock or gravel.

I've had some of these posts in for 20 years now and they haven't moved at all. The one for my mailbox even has the box hung on a 4 ft twistaway pipe so that when the snowplow hits it it just moves out of the way. This is the oldest one and it has stayed with no problems even with the overhung load and no back support.

I've also done this on fences with a heavy gate hung on the post.

I've built wheelchair ramps using treated 4 x 4 posts set on the ground on top of a 12 x 12 inch piece of treated plywood. The structure is loose and independent of the house. These posts just bear on the plywood. As an added plus, the plywood keeps grass from growing next to the post and cuts down on the trimming. This has also held up well, though it has probably moved over time. If the movement was too extreme, the post could be jacked up and the plywood re leveled.

If your building code doesn't specify anything specific other than footing depth, I wouldn't be afraid of setting the 4 x 4 or larger treated post in concrete as described above.

: The closest I can come to making this relevant is that I will likely haul parts and materials for building the deck in the Sub.
:
: I am putting a long & narrow porch/deck on the front of my house. The back edge will hang on a ledger. The front will be supported on posts. Deck height is 17" above grade and length/width is 46'x6.5'. My question is about the posts.
:
: Background -
: *I live in northeast Ohio and have significant snow and ice in the winter.
: *City requires supports to be set at least 36" below grade.
: *Ground water is not an issue.
: *The reputable guy at the lumber yard (small local place - not big box) says most everything I have read is overengineered for a small simple deck like mine.
: *All structural lumber is pressure treated.
: *Cost IS a factor - but I don't like to do things twice
:
: My question is: I have read about various methods for setting the posts. Set at/above grade on a metal base anchored in concrete, set in concrete, or set in the ground with compacted dirt or gravel.
:
: I have to believe that pouring a concrete pier and using a metal base is probably the best option but also the most expensive (cost for concrete and anchors). The two methods for setting the post in the ground are probably similar although it seems that not using concrete may be better for drainage and therefore longevity. I have also heard from people that used gravel as the fill around the post instead of dirt.
:
: I am hoping that with this forum's vast store of odd knowledge, that someone may have something to share that can help.
:
: More info/drawings on request.
:

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Comments:	: I live in Minnesota and my subsoil is clay so there are lots of frost problems (6 to 8 feet down in bare ground). In our situation... : : The concrete pillar with the post anchored to the top is very good design. The main thing is to include some rebar in the pillar. The concrete is usually poured in cardboard tubes. The tubes are fairly smooth on the outside and resist being lifted by the surrounding frost. : : This foundation system was even stable enough to anchor my old large satellite dish on a 3 point mount where frost movement would be critical. : : I've had good luck with fences with the following supports; I use a treated 4 x 4 set in a hole in the ground. I then back fill the hole around the post with dry quickcrete mix. A liberal application of water then sets the quickcrete in place overnight. This fills all the voids in the hole and prevents water from pooling in the clay like it would if I used crushed rock or gravel. : : I've had some of these posts in for 20 years now and they haven't moved at all. The one for my mailbox even has the box hung on a 4 ft twistaway pipe so that when the snowplow hits it it just moves out of the way. This is the oldest one and it has stayed with no problems even with the overhung load and no back support. : : I've also done this on fences with a heavy gate hung on the post. : : I've built wheelchair ramps using treated 4 x 4 posts set on the ground on top of a 12 x 12 inch piece of treated plywood. The structure is loose and independent of the house. These posts just bear on the plywood. As an added plus, the plywood keeps grass from growing next to the post and cuts down on the trimming. This has also held up well, though it has probably moved over time. If the movement was too extreme, the post could be jacked up and the plywood re leveled. : : If your building code doesn't specify anything specific other than footing depth, I wouldn't be afraid of setting the 4 x 4 or larger treated post in concrete as described above. : : : The closest I can come to making this relevant is that I will likely haul parts and materials for building the deck in the Sub. : : : : I am putting a long & narrow porch/deck on the front of my house. The back edge will hang on a ledger. The front will be supported on posts. Deck height is 17" above grade and length/width is 46'x6.5'. My question is about the posts. : : : : Background - : : I live in northeast Ohio and have significant snow and ice in the winter. : : City requires supports to be set at least 36" below grade. : : Ground water is not an issue. : : The reputable guy at the lumber yard (small local place - not big box) says most everything I have read is overengineered for a small simple deck like mine. : : All structural lumber is pressure treated. : : Cost IS a factor - but I don't like to do things twice : : : : My question is: I have read about various methods for setting the posts. Set at/above grade on a metal base anchored in concrete, set in concrete, or set in the ground with compacted dirt or gravel. : : : : I have to believe that pouring a concrete pier and using a metal base is probably the best option but also the most expensive (cost for concrete and anchors). The two methods for setting the post in the ground are probably similar although it seems that not using concrete may be better for drainage and therefore longevity. I have also heard from people that used gravel as the fill around the post instead of dirt. : : : : I am hoping that with this forum's vast store of odd knowledge, that someone may have something to share that can help. : : : : More info/drawings on request. : : : :
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