Building an Under-stairs Downfloor Closet

A downfloor is what we here in Japan call a descending split level. They are often used as an accent feature that “mixes up” the otherwise flat and mundane topography of your home interior. Having it in a highly visible place is the norm, such as the living room, but there are times when you want it to serve a more functional purpose.

Downfloor Beginning

Downfloor After

Before and after

For example, the space under the staircase is often converted to storage space, but under normal circumstances there’s not a whole lot of space under there. This is where dropping the floor a bit in this area can really make a big difference. The downfloor shown in the photos was part of a house we built recently, and details the steps, before and after etc.

As you can imagine, building the framing for the downfloor can be quite tricky due to the geometry of the staircase above. Obviously, complexity can vary considerably depending on how closely you want to follow the staircase shape. The more complex, the more head room. But the difference is often very small, and may not be worth the trouble.

One thing to remember here is to completely isolate the framing from the staircase. If any framing is contacting the staircase, there will be a chance of creaking. As people walk up and down the stairs, that kind of weight and movement will transfer to the framing underneath and you can imagine the effects – especially over time.

Tap into the surrounding walls and in most cases, the triangular angles will act to brace the framing in between the walls without having to support it in the center. Using plywood along with regular framing is recommended where the span is wider than you feel comfortable with, as it will serve to stiffen the entire framing network.

Downfloor step 1

Downfloor step 2

Downfloor step 3

Downfloor step 4

Downfloor steps

When building the stairs – even just one or two steps – there are two things you should know:

1. Use screws, not nails. Nails have the tendency to become loose as the wood expands, contracts, or ages. Loose nail shanks rubbing against the surrounding wood is a common source of creaking.

2. Along with screws, use glue (rubbery/urethane-based, or a similar durable type that won’t break easily or dry to a hard, plastic) on surfaces that are in direct contact with other components and have the potential for vertical movement.

Remember, it really doesn’t take a lot of movement to produce creaking, which is what makes this distinctive creaking of wood such a common occurrence with floors and stairs if extra care is not taken during the building phase. Also, even if it’s nice and quiet in the beginning, because wood is an inherently unstable material, it very often becomes a problem down the line.

Aside from the steps you can take, there are some factors in play over which you may not have control: ie, foundation settlement that puts stress on beams, subfloors, and surface flooring, creating gaps and room for movement; inherent material instability of all wooden components; long-term structural effects of earthquakes; or just good ol’ sheer and simple age.

In conclusion, when working with wooden floors and stairs, though it’s unrealistic to expect a lifetime or 2 of absolute silence, you can greatly enhance your chances of an overall, “reasonably” quiet house by following the advice in this article. Good luck!


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