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Jacking up screened-in porch (leveling)

Posted by vate (My Page) on
Wed, Jun 13, 12 at 7:26

I have a screened-in rear porch that was an addition to the house about 25 years ago. It is one story in the air - the space below it is an open lower deck. It is connected to the house on one end (joist board lag-bolted into the house studs). On the other end it is supported by three columns. For each column structure, there is a short steel hollow post, followed by the lower deck structure, followed by a longer steel hollow post(see photos). The steel posts are capped with rectangular steel plates with holes in them, lag-bolted to the house structure. All three of the short ground columns are mounted in concrete in the ground. The concrete (unfortunately) was not formed or poured into a pier on which the columns rest - they are buried in the concrete.

Over the 25 years the deck has settled slightly on the column side. It is not visually obvious, but the gutters no longer drain properly. I estimate that it has dropped about 1.5 inches. I believe most if not all of the settling occurred before I bought the house in 1997 (the gutters have never drained properly). There is no indication of twist - it seems to have dropped consistently across the back of the structure.

I’m getting a new roof and gutters on the house this year, and wanted to set the porch correct before I have the work done. Below is my plan and some questions - any comments or feedback would be helpful.

In short, I plan on lifting the porch using temporary jack posts, inserting spacers on the top of the existing upper posts, and lowering the porch down onto them. My planned steps:

Inspect the porch for separation from the house, ensure that the house side (joist) is properly attached.
Inspect the steel columns for rust and degradation, especially where they are tied into the concrete.
Install three temporary jack posts near the existing columns.
Jack up the porch slowly (one full turn per day)
Once the upper columms are clear, remove them, inspect them, paint if necessary. Replace any of the deck wood on which these rest today if needed.
Over-raise the porch about ¼ inch for clearance
Fabricate spacers
Reinstall original upper columns
Install spacers on top of columns. Attach columns and spacers to structure with lag bolts.
Lower porch slowly onto columns. Continue to tighten lags for correct alignment while lowering.

One question - I know that using steel or aluminum for the spacers would be ideal, but is there anything wrong with using wooden spacers? They would be easier to fabricate. The tops of the columns are about 8” X 8”. I would probably use ½ oak stock that I have (it was for drawers) and glue up pieces of it (using Titebond II outdoor glue) to get to my 1.5” thickness.


Follow-Up Postings:

RE: Jacking up screened-in porch (leveling)

wood no matter what type you use will compress and you will be back in the same situation. Use steel or if you do use aluminum remember to put something in to separate the metals.

RE: Jacking up screened-in porch (leveling)

Thanks for your quick response. Good idea on the aluminum - I've got a friend with a CNC plasma cutting table so he could fab them for me.

With aluminum against steel would I get a galvanic response (with oxidation)? Is paint a sufficient barrier?

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