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-   -   Replacing Porch Columns (http://www.diychatroom.com/f19/replacing-porch-columns-70903/)

mcwolfe6 05-10-2010 02:10 PM

Replacing Porch Columns
 
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We have decided to remove our support posts (4x4's) and railing on our front porch and replace the columns with 8x8 columns and no railing to give the porch a more open feel. We would like to remove the 8 columns currently there (6 along the front and 2 at the rear of the porch) and only use 4 of the 8x8 colums at the front.

1st question - can i remove the front 6 columns and only replace them with 4 columns (1 at each end and 1 on each side of the door)? will the span between columns be too great?

2nd question - how do i determine the structural weight of the front porch roof to ensure that the new columns can support it? each new post can support 10000 lbs.

3rd question - how do i know if the current support beam (which is 4 inches wide and spans the length of the porch) can handle the distance between the new columns/

4th question - do I need to replace the columns at the rear of the porch? The porch roof is attached to the house?

I have included a photo of the front of our house so that you can get an idea of our current setup.

Thanks for any feed back.

kwikfishron 05-10-2010 02:43 PM

Probably not, you really need a Structural Engineer to positively answer those questions for you.

How big is the beam?

What’s the span between post?

Is your beam breaking on one of the post you want to remove?

It may look like one piece of wood spanning the porch but I’m sure it’s not. It’s just painted up real good.

The post against the house are more than likely decorative but can't say for sure.

HooKooDooKu 05-10-2010 05:07 PM

Assuming the 1st floor wall and 2nd floor wall are flush, the weight of the front porch likely isn't that great. From the point of view of simply being able to support the weight, I'd bet a pair of 4x4 posts could hold it. But the real issue is how well the porch can support itself BETWEEN the posts.

I'm guessing the reason six 4x4 posts were used was so that the span between posts was relatively small allowing for the use of shorter joists. As a guess, I think 2x6s were used between the posts. Had they wanted to use only four 4x4 posts, they would have had to jump up to 2x10s (again, a guess) causing the roof pitch to be nearly flat or the front edge of the porch to sit too low.

So the only way you are likely to be able to switch to only four support posts is if you find a way to reinforce the joists between the existing posts. I doubt you'll find a way to easily do such a thing yourself using standard dimensional lumber, therefore as kwikfishron suggests, you would likely need to assistance of a structural engineer to determine your options.
So likely the only way you could leave the roof profile the same and switch to only four support posts would be if the joists that sfrom post to post could either be replaced by an I-beam, or doubled/trippled up (li
I bet two 4x4 posts could hold the weight... but the real issue is how well the porch can support itself BETWEEN the posts. The reason 6

mcwolfe6 05-11-2010 09:26 AM

Kwikfishron - I was thinking I would need to get an engineer in to look at this but was hoping someone on here may know the answers to some of my questions. to answer some of your questions...

How big is the beam? it is 4 inches deep and 6 inches wide but it's wrapped in aluminum so i can't tell where the breaks are but the total span is roughly 28ft.

What’s the span between post? 5ft from post to post with the exception of the span between the posts on each side of the door. that's about 7ft.

Is your beam breaking on one of the post you want to remove? It's wrapped in aluminum so I can't tell where the break is but posts i want to remove are the ones in the center of the rail on each side. they are only five feet from the end of the porch and I can't imagine the break would be at 5ft.

Scuba_Dave 05-11-2010 09:49 AM

It might not be a 4x6 beam
Could be made up out of 2x4's & framed out to what you see
You will need to verify what is under alum wrapping
Spanning 12' with roof & snow load might need more support

tpolk 05-11-2010 09:54 AM

yes you need to see whats holding roof up

mcwolfe6 05-12-2010 12:30 PM

Okay. I just spoke with the contractor that built our house and they are sending me a copy of the house plans. They told me over the phone that the porch support beam above the pillars is a triple stacked 2x10 beam. Would this beam be sufficiant to support the roof without sagging if we remove the support columns I mentioned previously?

Yoyizit 05-12-2010 12:37 PM

Quote:

Originally Posted by mcwolfe6 (Post 439943)
1st question - can i remove the front 6 columns and only replace them with 4 columns (1 at each end and 1 on each side of the door)? will the span between columns be too great?

Assuming infinitely strong columns, how much sag between columns can you tolerate, either cosmetically or structurally?

tpolk 05-12-2010 07:51 PM

depends on if there are open splices in beam between columns


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