Curved Staircase Help

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I am working on drawing an existing home in Chief, to start a remodel.

The staircase is curved and I am needing the model to replicate the existing staircase!

First, does anyone know how to find the angle of an existing staircase? (This might be a question for a carpenter!)

Second, how do I get the staircase in chief to match the existing staircase curvature? I don’t have an existing plan or PDF.

I appreciate any help!

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If the existing is truly is a radius, i.e., is a single arc then do this, then measure from the center point to the staircase to get the radius.

Once you have that, I usually draw CAD line in CA to snap to with the stairs.

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You can set the radius of a curved staircase in the 'Section Number' section of the DBX for the stairs. I see no reason why you couldn't do this in reverse by drawing a new staircase over the existing one if you have a PDF of the existing plan.

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17 hours ago, ericepv said:

You can set the radius of a curved staircase in the 'Section Number' section of the DBX for the stairs. I see no reason why you couldn't do this in reverse by drawing a new staircase over the existing one if you have a PDF of the existing plan.

Unfortunately, I don’t have an existing plan/drawing for this home or I would simply trace over the plan!

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17 hours ago, CharlesVolz said:

If the existing is truly is a radius, i.e., is a single arc then do this, then measure from the center point to the staircase to get the radius.

Once you have that, I usually draw CAD line in CA to snap to with the stairs.

I’m sorry, in my post I put that I’m looking for the radius, but I’m actually needing to know the angle or how curved the existing staircase is.  I’m sorry, I made a mistake by putting radius!

I am needing to figure out the curvature of the existing staircase in order to draw it accurately in Chief!

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51 minutes ago, RGerbig said:

I’m sorry, in my post I put that I’m looking for the radius, but I’m actually needing to know the angle or how curved the existing staircase is.  I’m sorry, I made a mistake by putting radius!

19 hours ago, RGerbig said:

The staircase is curved and I am needing the model to replicate the existing staircase!

Sounds like to me you need the radius and the tangent (angle) somewhere along the curve (or arc).

Just call me so we can chat.

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• Solution

This way may be easier to measure the existing stairs close enough in the field. I am still assuming that the stairs curve along a single arc as shown. It is using the Intersecting Chords Theorem which says that the product of the lengths of the segments of any two intersecting chords is equal. When you use perpendicular chords you can measure A, B & C close enough and calculate D and thus the radius of the existing stairs.

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SInce the treads are already built, make a template of a few of them (to verify their consistency) take one and add control lines using a square that plumbs the nosing overhang of the tread above (to subtract this), and then measure 6" in from either end of the template tread nosing and square a line 90 degrees off the front tread you can determine the rear offsets of the nosing overhang.  In chief you can draw the inner trapezoid fairly easily.  Then extrapolate the template tread using the control line offset measurements.

Now extend the front nosing line and the rear nosing line of the tread above out until they intersect and you will have your radius..

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2 hours ago, CharlesVolz said:

This way may be easier to measure the existing stairs close enough in the field. I am still assuming that the stairs curve along a single arc as shown. It is using the Intersecting Chords Theorem which says that the product of the lengths of the segments of any two intersecting chords is equal. When you use perpendicular chords you can measure A, B & C close enough and calculate D and thus the radius of the existing stairs.

Mark,

This worked!  The radius is 128" and looks perfect in my plan!  I really appreciate your help with this!