Porch Column Replacement

By Robert Robillard on Columns

Replacing Wood Columns With Fiberglass Columns

Replacing wood columns with fiberglass columns is usually a straight forward and easy project.  On a recent project we were asked to replace three wood columns, one of which was severely rotted and caused the porch to settle 1 inch.  A project like this requires a building permit and experience understanding and building a temporary supporting column / post.

 supporting a porch to Replace Wood Columns with PVC Columns

Steps For A Porch Column Replacement

1.  Jack the structure:

Normally when replacing columns I release pressure on the porch columns with a hydraulic jack, raise the roof slightly and then provide structural temporary supports to hold the porch roof weight while I remove the porch column.  This porch had a second floor and a roof – it was heavy.  Using a 4 ton jack resting on a 3×6 plank spanning the side and main deck beam we jacked the porch corner up one inch.

2.  Build a supporting wall or post:

Unsure of how the ceiling beam was constructed, we installed two temporary load bearing posts on either side of the column to support both sides.  These posts also sat on spanned planks to spread the porch weight on the deck frame.

A double 2×6 support post assisted from the front, street side of the porch.  This post was more precautionary, I looked at it as cheap insurance.

3.  Remove the old wood post.

Once removed we used the old post to establish measurements.  We also ran a string to check the porch for level.  It dipped 1 inch on one corner where the porch column base had rotted.  Tear down your existing wood columns. Use your hammer and your pry bar and tear out as much of the existing column as you can. Depending on how the columns were built, you may need to use a reciprocating saw to cut them out. Try to minimize damage to nearby walls, ceiling and floor.

4.  Replace the decking beneath the rotted column as needed.

5.  Measure and cut the fiberglass column.

Cutting round columns can be a challenge. Round columns are typically smooth, the shaft is tapered and made of wood or fiberglass composite.

Round columns have a consistent diameter on the bottom 1/3 of the shaft height which allows for cutting to adjust for fit. The columns top 2/3’s height have a slight taper.

Tip:  Make sure that you ensure you have concentric loading of the column. 100 percent of the bottom must come in contact with the deck or floor, and 75 percent of the top of the column must contact the beam or sofit.

To cut the fiberglass porch column I used an abrasive masonry blade, but a carbide blade works too. Remember to wear a dust mask.  Steps To support porch roof and Replace Wood Columns with PVC Columns

Secure the porch column to the saw horses with bungee cords.   Trim the porch column shaft [lower section for tapered columns] Minor adjustments can be made with a rasp, sander, grinder or the side of the masonry blade. Sometimes adjustments are needed to ensure you have even load distribution on the bearing surfaces.

6.  Check the column for plumb on two sides:

The bottom third of these columns is consistent enough to get a real plumb measurement from a level.  The tip two-thirds of the column is tapered and will throw off the level’s plumb buble.

7.  Install the new column

Replacing wood columns with fiberglass columns:  Stand the new PVC columns up as close to the desired application as possible. If you have trouble getting them in, shave off some of or jack the porch up higher.  Do not hit your columns with a hammer. PVC can shatter with enough force. When the column is in place lower the weight onto it and fasten it at the top and bottom with supplied support brackets.   Pre-drill everything going into a fiberglass column.

There may be brand-specific installation instructions enclosed in the box or directly on the box.Fiberglass porch post

We chose Poly-classic 8″ round columns with faux base and capital trim detail.  Poly-Classic offers architectural fiberglass columns that are suitable for use in load bearing applications.  They also offer decorative columns that are so effective in wrapping existing porch support posts.

Poly-Classic columns include FlameGuard, a features that makes the Poly-Classic FRP column the best column available when it comes to flame resistance. Poly-Classic Columns have a Flame Spread Index (FSI) of 15 and a Smoke Developed Index (SDI) of 335, resulting in a Class I Flame-Spread classification.

8.  Remove the suppoort posts and move to the next column:

When we got to the corner that had sunk we jacked the porch up to compensate for the sinking as well as a 1/2″ to get the new column in.

Related Posts:

Tips For Cutting Round Columns

Steps To Replace Wood Columns with PVC Columns

Replacing A Porch Column.



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About the author

Robert Robillard

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzzr As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising-the-bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

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