# temporarily supporting porch roof



## dom-mas (Nov 26, 2011)

I have to remove a brick column and rebuild. I want to support the porch roof (just a roof no live load) with 2x material attached to a stake maybe 6' back from the porch. the porch roof is about 10' above grade so the bracing would be greater than 45*, closer to 60*. Just wondering how deep the stake would need to be to not move (clay and loam type soil, not sandy). I'm thinking 2'-3' should be enough. Also what size braces I'd need. I'm thinking 2- 2x10-16's but wondering if 2x12's are warranted


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## dom-mas (Nov 26, 2011)

Oh, the other thing i could do, since the column is on the corner is to put a beam across the corner and use a shoring jack on either side. Any benefit to this? The drawback that I can think of is that I would probably have to have the jacks a bit closer to the column. But maybe not


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## Kowboy (May 7, 2009)

dom-mas said:


> Oh, the other thing i could do, since the column is on the corner is to put a beam across the corner and use a shoring jack on either side. Any benefit to this? The drawback that I can think of is that I would probably have to have the jacks a bit closer to the column. But maybe not


I've done this, it works, and is my favorite way.


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## dom-mas (Nov 26, 2011)

What's the benefit? did you put anything under the posts as a footing?


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## TheHomeTeam (May 3, 2014)

This was how I did one a few years ago when I had to rebuild a porch deck. The braces were 2x4's screwed together "T" style, and screwed to the scrap boards staked flat on the ground so they wouldn't slide.


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## dom-mas (Nov 26, 2011)

2x4 in a T huh? so 3.5+ 1.5= 5". so maybe 2x10 is even overkill


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## Dan_Watson (Mar 1, 2008)

I have seen houses leveled using the 2x4 t and a bottle jack...Just stay away when those things explode!


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## Dan_Watson (Mar 1, 2008)

dom-mas said:


> 2x4 in a T huh? so 3.5+ 1.5= 5". so maybe 2x10 is even overkill


Remember that the T shape 2x4 is not the same as a 2x5 (using his math). The two boards, perpendicular to each other, counteract the flexing/bowing. Think I beam.


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## TheHomeTeam (May 3, 2014)

Well I guess 2x6 would have been more conservative, but it worked the way I did it. But I did deliberately set them as close to vertical as I could and still have room to work, figuring it would be stronger that way, and to transfer the load more straight down than out at an angle.


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## dom-mas (Nov 26, 2011)

Dan_Watson said:


> Remember that the T shape 2x4 is not the same as a 2x5 (using his math). The two boards, perpendicular to each other, counteract the flexing/bowing. Think I beam.


really? The two 2x's are oriented in the same strand direction. The roof can only fail in 1 direction so as i see it there's only 1 direction that you need to put the strength (to a point obviously). 

But if you guys thing that 2-2x8's would be enough, I'd do that. I want to have enough material that I can make a check to bear the roof on, like a reverse birdsmouth. But then again with the T'd 2x4's (I'd probably go 2x6's just to make me feel better) I could just lower the one 2x to bear on the beam of the roof.


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## superseal (Feb 4, 2009)

I usually slam two 2x6's together in a sandwich and pepper them with nails.

Bird mouth the top cut and dig a small kicker in at the bottom - of course I'll usually have post jacks in place somewhere so I can slightly jack up the roof to release the column. stakes go down about 18" to 24"

Could also use a permanent steel or wood posts in place, then just build around it if your not changing out the footing.


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## TheHomeTeam (May 3, 2014)

A peice of 2x can handle immense weight if it is straight down like a column, as long is it is prevented from bowing. The T shape makes them way more rigid to avoid bowing out and snapping under load.


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## dom-mas (Nov 26, 2011)

Thanks SS. That's about the angle I'll be dealing with. enough room to work. yes I'll be repouring a footing. Also the porch is supported by the column which is typical for homes of this age (1920s-30's) around here. 

If 2-2x6 is enough That's what I'll go with and save myself $80


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## dom-mas (Nov 26, 2011)

TheHomeTeam said:


> A peice of 2x can handle immense weight if it is straight down like a column, as long is it is prevented from bowing. The T shape makes them way more rigid to avoid bowing out and snapping under load.


Right and that's the issue. I want and need as much space as i can get around the work area. The 2x4 on it's side is only 1/2" thicker than 2 2x4's sandwiched together. I think that 3" is enough to keep it from bowing laterally but would still like a bit more mass to keep it from deflecting. I might even beef up to 2x8 because they used A LOT of wood in these houses in the 20's and the porch is a good 3' above grade making the height closer to 10' maybe a bit more


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## Dan_Watson (Mar 1, 2008)

dom-mas said:


> *really? The two 2x's are oriented in the same strand direction. The roof can only fail in 1 direction so as i see it there's only 1 direction that you need to put the strength (to a point obviously). *
> 
> But if you guys thing that 2-2x8's would be enough, I'd do that. I want to have enough material that I can make a check to bear the roof on, like a reverse birdsmouth. But then again with the T'd 2x4's (I'd probably go 2x6's just to make me feel better) I could just lower the one 2x to bear on the beam of the roof.


The 2x are perpendicular to each other. And the roof can come down, or pull away, but the 2x is not perfectly vertical so there are other loads on the 2x that will make it bow. 

Think about strong backs, gable ends, why trusses need to be braced so much....putting 2 pieces of lumber, perpendicular to each other and fastening them properly makes one hell of a strong member.


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## dom-mas (Nov 26, 2011)

Dan_Watson said:


> The 2x are perpendicular to each other. And the roof can come down, or pull away, but the 2x is not perfectly vertical so there are other loads on the 2x that will make it bow.
> 
> Think about strong backs, gable ends, why trusses need to be braced so much....putting 2 pieces of lumber, perpendicular to each other and fastening them properly makes one hell of a strong member.


I understnad that, but as i said above...a 2x4 is only 1/2" wider than 2 2x4's nailed together. I would think that 3" is enough to stop any bowing especially seeing how there are 2 other existing posts stopping the roof from moving


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## Dan_Watson (Mar 1, 2008)

So after all that we agree.. ha


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## Kowboy (May 7, 2009)

dom-mas said:


> What's the benefit? did you put anything under the posts as a footing?


I run a doubled 2x10 across the corner supported by a 4x4 on each end with a screw jack and plywood pad under each end. Level the plywood and plumb the 4x's. Unlike the other methods shown, this system is adjustable so you can raise your porch a tad, then set it right down on your columns. If the 2x10s are long enough, the 4xs are out of your work area.


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## RobertCDF (Aug 18, 2005)

superseal said:


> I usually slam two 2x6's together in a sandwich and pepper them with nails.


I've seen doubled 2x's start to bow under weight, a T is SO much stronger. Next time try the T you'll be a lot happier with the results.


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## RobertCDF (Aug 18, 2005)

2x4 T posts are all that's holding up this deck and pergola, the piers had not been poured yet.


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## pwagg3712 (May 1, 2014)

https://courses.cit.cornell.edu/arch264/calculators/example7.1/index.html


Only thing stronger than a T shape is a square maybe some 4x4's. it all comes doen to how the brace is pinned to the ground. for under 100 bucks you can get a pretty strong metal shape 20' long,, metal does better with bending. don't know if you have already done the work but I can do some BASIC structural calcs for you. what are the dimensions of the overhang covering the porch,, what is the distance to the next column or bearing point


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## pwagg3712 (May 1, 2014)

really I just send it to my amigo who is a structural engineer


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## dom-mas (Nov 26, 2011)

Well i didn't use any of those approaches. The ground is so thick with roots that I couldn't get a stake more than about 6" deep an I tried in quite a few spots. Worst digging ever, did more work with the sawzall and a pruning blade cutting roots than with a shovel.

ended up supporting the deck and putting a post up on either side of the column, bearing on a plate to spread the weigh. it's not ideal because it leaves me less room to work but any beam I made to go across the corner would have to be 14' to avoid the stair and the hole we dug. Anyway, it's solid


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## Jeff G (Apr 5, 2010)

Yeah, Dom-mas, I was going to say that I've done quite a few of the temporary t-posts, or doubled 2x's, bearing directly on some type of 2x cribbing sitting on top of a larger piece of 3/4" plywood, if (and I do emphasis the word "if") there isn't much of a load. In fact, on light enough loads, I've even done this on just a piece of 3/4 plywood large enough to evenly distribute the load.

Then again, the entire shoring you're proposing (or anytime any of us do this) depends entirely on the loads imposed on the column (posts), the length of the columns, even the species of wood used for the columns. 

In reality, the ultimate stresses that would actually cause failure in the column is variable due not only to live/dead loads placed on it, but also due to defects, size and location of knots, lumber density, and even moisture content. If you're interested, there is a formula we can use to insure a safety factor to let us know that the loads placed on any column/post will result in it buckling so badly it could fail under those specific conditions. I usually will implement the calculation of all this if I am questioning the situation at all. It helps me to better design my posts, or spacing, footers, etc, in order to prevent a disaster. But suffice it to say (and as already mentioned) that the t-post will resist buckling more so that if the same two pieces of dimensional lumber were tied together with the grain running parallel.


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## dom-mas (Nov 26, 2011)

I'm still just confused as to why the grain is running in a different direction if it is in a T rather than doubled up. The grain is still running vertically. Only 2 directions for grain right?

And for this sort of stuff i prefer to just overbuild. There is virtually zero weight anyhow. The porch is maybe 24' long with a post @ the far corner , then another at the steps that are about 4' wide then the post I'm working on. Most of that roof is cantilevered from those 2 remaining posts. The column came down so easily that there was no way any serious weight was on it. 

By the way. how common are hollow wood columns in other areas? Around here hollow 8x8-12x12 columns made of 1x material are the usual in the older neighbourhoods.


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## Jeff G (Apr 5, 2010)

dom-mas said:


> I'm still just confused as to why the grain is running in a different direction if it is in a T rather than doubled up. The grain is still running vertically. Only 2 directions for grain right?


Posts rarely fail in compression unless they are very short. Most often a post will fail in buckling. That is why the carrying capacity of a post/column is always based upon its L/r ratio, or "slenderness" ratio. In other words, the post will buckle in its thinnest (slenderest) dimension (which is what it must be designed for). The t-post will simply increase the slenderest dimension (provided it is sufficiently tied together with proper type and placement of fasteners to resist shearing).


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## dom-mas (Nov 26, 2011)

Yeah Ok, I understand that. it makes sense with 2x6, but a 2x4 it only increases the width by 1/2".


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## Jeff G (Apr 5, 2010)

dom-mas said:


> Yeah Ok, I understand that. it makes sense with 2x6, but a 2x4 it only increases the width by 1/2".


I know a 1/2 inch sounds insignificant, but it can mean a lot when considering buckling of a post (also depending on some of the other factors I mentioned earlier). Kind of like what you were talking about when "overbuilding" something. I tend to err on the side of overkill myself. If I can make a post stiffer, even by a little bit, I typically do. Under small loads, buckling really doesn't come into play, especially if one simply exercises good common sense when placing the temp shoring.

Sounds like you've got a good handle on everything, Dom-mas!:thumbsup:


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## RobertCDF (Aug 18, 2005)

I've seen idiots try to jack things up with a bottle jack and 2 2x6s nailed together (like a double) and that post will bend, I've shown them a 2x4 T post and it lifted the load no problem.


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## Walrus11 (Oct 3, 2021)

RobertCDF said:


> I've seen idiots try to jack things up with a bottle jack and 2 2x6s nailed together (like a double) and that post will bend, I've shown them a 2x4 T post and it lifted the load no problem.


What the heck is a 2x4 T?


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## Tinstaafl (Jan 6, 2008)

Also called a strongback. You're not a contractor, are you?


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## Railman (Jan 19, 2008)

2x4 T will support huge loads. Even better when jacking with one is to use a 2x piece flat ways so small bottle jack ram top don't pierce and compromise 2x4 T bottom.


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