A pony wall is a small wall that is not more than a wall. It is also sometimes called "knee wall" and "cripplewall". This guide will help you understand what pony walls are, as well as how to make one.
Pony walls can be described as walls that are short and carry floor joists where there is no foundation. They also include non-structural walls that act as room dividers and guards for balconies or stairs.
Another example of a structural example is the short walls that rafters often bear in Cape-style houses. These walls are almost always called "knee walls".
Pony walls are a very short wall and can be used interchangeably with "kneewall" or "cripplewall".
Pony walls are similar to regular walls. They have top and bottom plates. These are the horizontal members that the vertical screws attach to. The spacing between the studs is the same as elsewhere in the house, either 16 or 24 inches. Exterior walls such as foundation walls are covered with structural sheathing, such plywood or OSB. The interior pony walls are drywalled, and then finished.
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Load Bearing Pony Walls
Pony walls should be framed in a way that aligns with the floor joists. If the pony wall extends from a foundation wall's wall, the studs should be placed so that they are below the floor joists.
Attic knee wall studs should be below the rafters. This allows for easier wiring and plumbing, as well as creating what is known to be a continuous load path. This means that each framing member (e.g. a stud or joist) bears directly on the member below it. The path continues all the way to a beam, or to the foundation.
To prevent rot, the bottom plate of a pony wall that rests on a concrete slab or foundation should be made from pressure-treated lumber. Code requires that the bottom plates of pony walls resting on a foundation be bolted to concrete. This is similar to the mudsills that connect the rest of the house framing and the foundation. This is done to prevent the building's shifting in earthquakes and very high winds.
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Interior Pony Walls
Many pony walls are not designed to carry a significant vertical structural load. They don't have to be strong, however. A pony wall should not be used as a room divider that can be moved if someone leans against it.
A pony wall needs to be strongly anchored because the wall acts as a lever for someone pushing on the top. This is easiest when the pony wall meets a perpendicular walls. You can fix or screw the pony wall's last stud to studs, or block in intersecting wall braces that finish well.
It is more difficult to build a rigid pony wall if its ends (or end) are located in the middle of a floor. It won't be enough to attach a wall to the floor by framing it and nailing it down.
Good carpenters will cut holes in the subflooring to allow the end stud to be extended into the floor framing. If you are lucky enough to be able to plan the floor and wall layouts beforehand, the stud should lie directly next to a joist. The two can then be joined using lags and structural screws. Blocking between the joists and the stud is a good option if the stud falls in the middle or center of a joist bay.
Pony walls are often used in bathrooms to provide privacy for the toilet, shower, vanity or partially enclosing an soaking tub. These pony walls are often tiled so waterproofing is essential.
Stair and Balcony Walls
Code requires that guardrails for residential balconies and stairs must be capable of supporting a 200-pound sideload. They must also be at least 36 inches above the noing of the stairs, or the finished floor of the balcony.
These rules also apply to pony walls. While it is possible to measure the height of the guard, there are no reliable methods to determine its side load capacity. Carpenters build them as strong and durable as possible.
The pony wall is built using continuous studs to guard stairways. These studs are connected to the rough stringer by lags or structural screws. This ties everything together in a fixed assembly.
This works well if you're closer to the top of a stairway, but at the bottom the wall creates a lever which can overcome a simple connection stud-to plate. This is where the floor framing should be found below.
The balcony walls' ends almost always end up being braced with other walls. If the balcony turns, it may be another pony wall. The pony wall at the stair ends where one end meets the other. These connections provide all the strength required for residential situations.
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