roof support posts

[ET1 SS]

I am thinking about building an additional roof to wrap around the outside of our home.

Bolted to the building under the current eaves, going out 8-foot to vertical posts.

We are not interested in building a deck, thinking instead of filling the area underneath with pea-gravel and flag stones.

I had assumed that I would need to dig holes and set concrete cylinders down to below the frostline, wrapped in plastic, to support the posts. Generally this is what people around here do. Cardboard 'sonotube' 5 foot in the ground inside of two layers of plastic, then filled with concrete.

But now I have seen at homeDepot these post anchors.

http://www.homedepot.com/buy/lumber-...ces-88904.html

http://www.homedepot.com/catalog/pro...6f5657_300.jpg

Looking at these I do not think that the frost could heave them.

I would like to hear what you folks advise.

Do you think that these anchors would be enough to support posts holding a roof? Or Would I need concrete?

Thanks.

[Danaus29]

Check to see if what you want to do is covered under any local building codes first.

[motdaugrnds]

Exactly, Danaus29, I would definately ask your county's building inspector for some advice.

[Darren]

That doesn't do anything to increase bearing capacity like the concrete would.

[tiogacounty]

If you have to answer to any type of inspector, the answer is no. They have no real definable load bearing capacity. They rely on soil friction and not a calculated PSI load bearing. In other words the bottom of the sonotube concrete pier bears on a flat soil. The soil has 1500 PSF of bearing capacity, and the diameter of the tube is X resulting in Y # of sq. inches of bearing, so the pier is clearly capable of supporting the load, or not. As a builder I would not do it for a customer. However, if I had to answer to no one, I might try it on my own house. If you fail, and get settling on a post or two, it really isn't rocket science to temporarily support a porch beam and install a poured pier. Good luck, it sounds interesting. BTW, the going rate to have a pier hand dug in these parts is $40-50, including hand mixing the concrete. Once you add seven bags of concrete and a 4' x 12" tube, it adds up.

[ET1 SS]

Thanks.

We do not have a town inspector, nor any county inspectors. The only inspectors that would apply here are state, if you force them to come out, they disapprove everything.

I have now been told that being steel, they conduct temps fast so they will freeze the soil around them faster and thaw faster, which will create even more frost heaving.

Thanks everyone

[Cabin Fever]

A little off topic, but since you're in snow country I have a few off-topic questions.

What slope will the new roof be at?

Is your current roof steel or asphalt? What are you planning for the new roof?

Do you currently have any problems with ice dams?

[ET1 SS]

Originally Posted by Cabin Fever

A little off topic, but since you're in snow country I have a few off-topic questions.

What slope will the new roof be at?

Is your current roof steel or asphalt? What are you planning for the new roof?

Do you currently have any problems with ice dams?

My current roof has a 1-foot rise/10-foot run slope. It is steel. After 5 years it has never had any ice dam issues.

The eave is 12 foot high. I plan to drop down 2 feet and start this new roof there with about 3-foot rise/8-foot run slope. The posts being 8-foot from the building.

This wrap-round porch roof will have plywood and then sheet metal.

[Jim-mi]

What type soil conditions do you have. If gravel/rocky would those things be drive-able to a below frost line depth ?.

[rambler]

Originally Posted by ET1 SS

My current roof has a 1-foot rise/10-foot run slope. It is steel. After 5 years it has never had any ice dam issues.

The eave is 12 foot high. I plan to drop down 2 feet and start this new roof there with about 3-foot rise/8-foot run slope. The posts being 8-foot from the building.

This wrap-round porch roof will have plywood and then sheet metal.

Wow, that is a shallow roof if you are in a snow area, you have to plan to hold all the weight, no slide-off. (Edit - sorry for my bad spelling/typing/lack of proofreading.)

Your porch roof math doesn't quite come out - 12 foot eve minus 8 foot post is 4 feet, minus the 2 foot drop, equals a 2 foot rise in the 8 feet.....

Around here you need to be careful of the snow loads, when you put in drops and change roof angles, wind and snow can make for some very, very interesting snow loads as melt-off changes, drifts pile up. I don't know if this is a concern in your area.

The post anchors you picture are commonly used by real estate places to easily put up and take down their for-sale signs. I don't think it has much of any load bearing ability. I'd maybe try them for a small free-standing car port if I wanted to have fun, but I would not use them as a part of a house addition, even if 'just' a porch.....

--->Paul

Added: The snow let go on my barn this winter, and crushed in the metal chute on the silo. I don't mean dented, I mean _crushed_. It was wicked this year.

[Cabin Fever]

Rambler pretty much addressed the concerns I had when I raised my questions above. I would be concerned that on some warm day the snow load on your home's roof might let go and slide down on top of the new porch roof and crush the structure.

[oregon woodsmok]

Snow load and the possibility of the wind getting under the edge of the roof and flipping it off the house.

So you want to be sure you have enough load-bearing capability and that the posts are anchored securely to the ground and the roof anchored securely to the posts.

[michiganfarmer]

like others here, I dont like them either.

They dont have much flat bottom to suport weight. I tent to think they will sink, and looking like a grade stake, they make me think that a strong wind under the roof might pull them out.

Im not a builder by profession, but Ive built, and helped build a few houses, and a dozen pole barns.

[artificer]

The foundation has two purposes. Support the roof and keep it anchored in an uplift situation. The metal spikes will hardly do either. I know of someone that used sharpened greentreated posts as a porch foundation. Each year he goes out and cranks up the threaded post supports to fix the sag. Not my idea of a good situation. (basically what michiganfarm said)

I would go with either the concrete posts, or a post pad and treated 12' posts.

Michael

[davel745]

Here is what i would use

http://www.sonotube.com/products/son.../tubebase.aspx

Dave

[Beeman]

I've never lived in as cold an area as yours, but even down here I would use a concrete footer deep enough to prevent heaves.
Doing all of that work I would go for 10' at least, 8' isn't much when you start using it. The sliding snow load Cabin Fever mentioned might be a problem. You'd have to tie to your existing structure pretty good, possibly add posts against the building and use heavy rafters. How much wind do you deal with?

[ET1 SS]

Our house is steel. I spoke last summer with a local engineer/contractor that I trust. He suggested that if I lag-bolt a horizontal 2x6 to my horizontal purlin [which is located at 7 foot high] that no further support will be needed where this roof attaches to my house.

He was assuming that I would then be building a deck, which is what everyone else does. But even a deck must have piers with footers below the frost line, or else it will heave.

After much thinking, we really do not want a deck. Posts supporting a roof, a below grade leech line to carry away any surface water, a layer of fancy gravel and some flag stones should be okay.

I saw these post anchors being sold, so I asked. Everyone agrees they are a bad idea. So I am fine with that. As I said before I now know that these anchors will not work.



As for wind we occasionally get 40 knot gusts.

[Beeman]

Wind can get under a roof like that and lift the whole thing up and carry it away. I see a lot of metal roofs that get peeled off when wind gets under them.
I wonder how those supports would work if you sunk them into the concrete?

[ET1 SS]

Our foundation goes down 8 foot to a footer and has a good deal of rebar in it. Each vertical column is bolted onto 18" anchor bolts that each in turn were fastened to rebar before the concrete was poured.

I would be tempted to put some rebar into the concrete forms and attach the bracket that holds each post to the rebar.

[haypoint]

Originally Posted by ET1 SS

Our foundation goes down 8 foot to a footer and has a good deal of rebar in it. Each vertical column is bolted onto 18" anchor bolts that each in turn were fastened to rebar before the concrete was poured.

I would be tempted to put some rebar into the concrete forms and attach the bracket that holds each post to the rebar.

Those tubes are pricy. I'd use a 12 inch post hole diggeer, go down 48 inches, clean out the hole and use a short piece of tube at the top. I would use the tube to insure that the concrete didn't form a mushroom near ground level. That mushroom would allow frost to heave the post.

If the post is deep into concrete, it has stronger side to side strength than a post fastened to a bracket at ground level.

At some time, that roof will need to support all the snow from the house roof, plus a couple inches of rain. It happens. Wet snow crashing down 2 feet onto your addition would require some strong rafters.

Is there any way you could fasten the new roof's rafters to the sides of the current rafters? I'd want to try to maintain the same pitch. Then the next time the roof gets replaced, you could run from house peak to addition eave.

Roof pitch is measured in drop over a span of 12. A 1:10 that you say you have is very flat. Few homes have less than 4:12, 6:12 in snow country.