How do you build winder stairs to save space?
Personally I hate winders, but if you don't have room for a landing, here you go. Here is what the Canadian Building Code says on this subject:
Where a stair must turn: the safest method of incorporating the turn is to use a landing, Inside a dwelling unit however, where occupants are familiar with their environment, winders are an acceptable method of reducing the amount of floor area devoted to the stair and have been shown to be no more hazardous than a straight run of steps. Nevertheless, care is required to ensure that winders are as safe as possible. Experience has shown that 30° winders are the best compromise and require the least change in the natural gait of the stair user. The Code therefore permits only this angle. Although it is normal Code practice to specify upper and lower limits in this case it is necessary to limit the winders to one specific angle with no tolerance above or below this angle other than normal construction tolerances. One result of this requirement is that winder-type turns in stairs are limited to 30° (one winder), 60° (two winders), or 90° (three winders). It should be noted that winders are not permitted to converge to a point.
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As you can see the Code is in metric, however I'm not. Notice the line of arrows marked 251, 259 and 251 around the winders. This is called the line of travel and should be the same run as the rest of the set of stairs.
This line of travel is about 18" from the inside of the steps. This is what causes the winders to trip people if it is too narrow here.
The pointed part of the winder on the inside should be no less than 6" wide, in other words, they cannot come to a point. For this to work, the normal line of the landing comes down the stairs almost a run and the upper set of stairs goes above the normal run and the upper set of stairs goes above the normal line of the landing by the same amount. So, instead of gaining two steps, you lose two, which is about the same for a landing anyway.
Also you mentioned wanting to put in four winders. The code says three is the max with 30° each making a turn of 90°. Lay your particular situation out to scale on a piece of paper to see actually how much you gain and if it is worth the hassle. I learned this from experience when I was renovating for my daughter. I laid the stair opening out expecting to gain two risers and three runs. Wrong! It doesn't work that way. I ended up cutting the opening bigger and putting in a landing.
To see some photos from a member on a set of winders he built see photos.
Dave(Ask Dave) (About Dave)
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