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Repairing the Wood Porch on Your Historic House | Wisconsin Historical Society

General Information

Repairing the Wood Porch on Your Historic House

Repairing the Wood Porch on Your Historic House | Wisconsin Historical Society

If you own a historic house, it probably has (or had) at least one wood porch. An open porch that provides homeowners with a place to sit in the shade and watch over their neighborhoods is the hallmark of most historic houses. Open wood porches are often adorned with delicate moldings and gingerbread, making them vulnerable to weather- and moisture-related problems.

Your historic wooden porch might exhibit any of the common types of damage described below. You can repair some of these types of damage yourself, while others will require the services of an experienced carpenter.

Sunk Footings

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The right side of this porch floor is sagging due to the pier footings failing. Source: Bob Yapp

Most historic wooden porches were built on masonry pier footings. A pier footing is a brick or stone column that supports the entire weight of the porch. Piers were typically installed under columns or porch posts. If the footings at the bottom of the piers supporting your porch were not installed below the frost line, your footings could heave, settle or deteriorate and fail entirely. A pier failure can cause a column to sink, as well as the deck framing and the box beams that rest on top of the column.

If your porch has sunk or settled significantly, a professional masonry contractor can dig around the original pier and footing to make repairs. This work will often require the wood deck, columns and roof to be supported while the old footings are removed and new footings are installed.

Rotted Posts and Beams

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The base of porch columns are susceptible to deterioration due to excess moisture and abrasion. Source: Bob Yapp

Since most wood porches were designed to be open to the weather, wood rot is a common and sometimes serious problem. If you do not regularly maintain the paint and caulk on your porch, wood rot will be inevitable. These two areas of your wood porch are the most vulnerable to rot:

  • Column and porch post bases. The bottom of any column or porch post is the end grain of the wood. Moisture wicks into end grain more than any place on a piece of wood. As a result, rotting is common on the bottom of structural columns. You can hire an experienced carpenter to remove the rotted portions of columns or posts on your porch and add new wood. This repair is called “adding a Dutchman.” The carpenter will first jack up the porch roof, then add the Dutchman repair and set the column back down onto the deck and piers.
  • EnlargeImage of failing porch, with sagging box beam.

    The box beam resting on the columns is clearly sagging. Source: Bob Yapp

    Box beams. Most historic wood porches have a horizontal beam that rests on top of the columns. These beams are often a hollow box beam instead of solid dimensional lumber nailed together. Box beams hold up the entire roof framing structure. Box beams can rot or sag. Moisture from a leaking roof can cause structural rotting of a box beam. A box beam can sag if it is structurally weak or the distance between two columns is too great. 

    You should hire an experienced carpenter to repair a rotted or sagging box beam. The carpenter can replace rotted portions of your box beam without jacking up your porch roof structure. However, if you have a sagging box beam, the carpenter will need to jack up the roof structure to take pressure off the box beam. The carpenter will remove the old beam and replace it. It is best to replace a hollow box beam with 2- x 8-inch or 2-foot x 10-inch or 2- x 12-inch dimensional lumber ganged together to create a very sturdy beam or header. Have the carpenter cover the installed beam with 1-inch x material to make it look like your original hollow box beam.

Rotted Flooring

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The ends of tongue and groove porch floor boards are typically the areas in which deterioration occurs first. Source: Bob Yapp

Most historic porches have 3-1/4-inch wide x ¾-inch thick tongue and grooved fir or pine flooring. Fir was used most often because it was harvested from old growth trees and therefore was more rot resistant. Porch flooring is most vulnerable to rot on the exposed end of the individual boards and around columns.

All porch framing should have a 1/4 inch pitch per foot. For example, if your porch floor extends six feet out from your house, the pitch from your house to the outside front edge of the deck should be 1-1/2 inches. A pitch less than this will not allow water to run off the porch effectively, causing wood rot to the flooring and structure below.

You can patch in new wood pieces into areas where the old wood has rotted. Tongue and grooved fir porch flooring is readily available in nearly the exact same dimensions as historic porch flooring. Be sure to hand-pick your new fir floor boards at the lumber yard. As you sift through the stack of fir flooring, look for quarter sawn or rift sawn pieces.

Rotted Steps and Balustrades

The open wood steps of your historic Wisconsin porch are constantly exposed to rain, sleet and snow. Your porch steps can rot away if you do not maintain them with caulk and paint. You can often repair minor problems with rot using architectural epoxies.

The balustrade (railing system) of your porch is also vulnerable to both rot and sagging. If the balustrade between two columns is not supported in the middle and the distance from column to column is too great, your, balustrade could sag. You can help support this railing system by adding a block of wood under your sagging balustrade midway between the columns or posts. You can often repair a rotted baluster (spindle) or railing by splicing in new wood. In rare cases, you might need to replace the entire railing or baluster.

Leaking Roof

A leaking porch roof is more than merely annoying. Water that penetrates a deteriorating roof can cause wood rot to the structural roof frame and the box beams that support the roof. The best approach to this problem is to prevent damaging leaks by keeping your porch roof in good condition.  Perform annual roof inspections for any missing or damaged shingles or for flat roofs, any possible penetrations in the roof membrane.