Investigating Your Back Porch: Structure and Upgrades
As a popular design feature of the Chicago bungalow, the back porch has been a staple in many homes throughout the years. Being either open to the elements or enclosed, they provide a semi-outdoor space that lets you enjoy a nice iced tea on a sunny day, while retaining the classic bungalow look. But with many of these porches being added or modified later by unknown builders, it is worth checking out first hand some potential problems that could be present, as well as corrections. If you are considering modifying your porch, then it is important to note what steps may be required to pass inspection. In this article, we go through some important steps to check when investigating the structure of your porch.
This is perhaps the biggest and most important category, as the porch is literally just wood framing members only. But as the structure may have been built by novice or inexperienced craftsmen, it’s important to check out the story.
To first break it down, the overall structure (superstructure) of your porch is most likely what is called a ‘post and beam’ framing system. This means that there are basically giant ‘beams’ that hold up the floor framing, which are then supported by ‘posts,’ which are attached to the ground (concrete).
In investigating the superstructure, if the porch is unenclosed, look at where the wood post meets the concrete. In a correct scenario (to Chicago code) the wood post will be mechanically attached to the concrete foundation either by being embedded in the concrete or by sitting on a metal post bracket. If your porch is older than around 1980, then it is probably the prior. However, if you are noticing that the post is simply resting on top of the concrete foundation with no attachment, then that is an area of concern. It means the structure is only held down for gravity, and not for any side to side or uplift from wind. The fix involves retrofitting a post bracket, which requires heavy jacking and bracing, and thus the help of a licensed contractor.
(Click to enlarge) Left: This wood post is not connected to the pier below, and the concrete pier is undersized in this case. Right: A typical post base.
At the same time you are looking for where the post touches the ground, you will also want to check and see what size of concrete pier foundation is present. Though there is no hard and fast rule for quickly assessing if a pier is the correct size, common sense prevails here.
Each porch will have different weight (load) on it, so correct calculations are required. However, if you notice that the pier is only about 1 or 2 inches wider than the wood post, it should signal a red flag. The problem with an undersized pier is that it will gradually over time sink into the soil below. This is assuming the pier is not sitting on hard rock below, which is impossible to tell without excavation (or X-ray vision!) Again, have your local professional do a visual inspection to determine if the structure is adequate.
Another problem may be present with the floor framing and supports. If your porch or deck is an open one, then the chances are the decking is running perpendicular to the house. This was designed so that the water would run off and away from the building, and not pool up if the boards were with or parallel to the house.
Floor framing is almost always run perpendicular (or 90 degrees) to the deck, which means that the framing members are oriented in the long direction along the house. If you are able to get underneath the structure with a flashlight, first check if the joists are connected to the beam (along the perimeter) with what is known as a joist hanger. This will be a metal bracket shaped like a ‘U’ that slips under the joist to “hang” it from the beam. Many older decks do not have these pieces and are relying only on the nails from the other side. To reinforce your structure, you simply need to add these joist hangers. If you are up for a little DIY for this fix: First, measure the width and height of the joist. Next, go to a home store and find the appropriately sized joist hangers (often with brand name Simpson Strong Tie) as well as the correct fasteners. Finally, slip the joist hanger around the joist, nailing it to both the beam and the joist. Should you not feel capable of adding these elements yourself, a professional is always available for this task and others related.
(Click to enlarge) Left: The joists are simply end nailed and not using a joist hanger. Right: A corrected hung and installed joist hanger.
The Chicago bungalow is now nearly 100 years old in some cases, with the back-porch additions being just as old. In the time since these porches were first being built, the Chicago code has been updated to reflect higher safety concerns and higher weight thresholds. As it is the duty of any licensed architect to uphold the health, safety, and welfare of a building’s inhabitants, we design all new structures to this code, including remodeling. Though existing structures are not mandated by law to abide to new codes, it is still good practice to always examine older structures to get a good sense of their condition. If you feel your porch and deck is an unsafe structure in any way, please reach out to an architect, engineer, or contractor to have them do a thorough inspection. In any case, having more knowledge of your home is always a beneficial thing.
Parker Brock is an ex-carpenter and licensed architect in the state of Illinois who manages the architecture firm Orlynbock Design in Chicago.