How can I make a coil with relief (volute)?

I'm trying to model a facade of an arch and I need to create a spiral as shown in these two photos.

I tried using the addon "Add curve: Extra objects" to create the spiral but I can not remove the smoothing of vertices. Besides, I'm not sure if I'll have any problems when I change the mesh to adapt the spiral. Note that the figure in the pictures has a relief.

Is this the best way to model the figure?

Note: I'm learning Blender and I followed these instructions.

There are probably many different ways to achieve it. I used Extra Objects and F2 add ons.

Start with adding a Spiral (Add-->Curve-->Spirals). Play with its settings in a Tool Shelf (T)

Convert your curve to the mesh (press Alt+C-->Mesh from Curve). Then select the whole mesh (A) and extrude it (E) as pictured below.

Being in Edit Mode add a Circle with the equal number as the Spiral's steps number. Extrude the Circle and use the snapping tool to snap its edge loop to the bottom vertex of a curved mesh. Now use the knife tool (press K,LMB, next C for a straight cut and then Z to cut through) as pictured below. Delete vertices above and below added cuts.

Fill the gaps with F (enable the F2 add on). You may also use the bridge tool to do it.

If you want to sharpen edges with edge loops (Ctrl+R) retopologize the top part as pictured below. This kind of geometry'll also smooth the end of the curvature.

Here's my final topology (with no tris and n-gons), that allows me to crease the edges.

Use proportional editing with a Sharp falloff type to adjust volute's proportions as you like.

• It's what I want! I created my model following your detailed tutorial. Another way might be this, with an array. I tried it before reading your answer. However, I think your solution is more accurate. Thanks @Paul Gonet – Jesus Gomez Feb 12 '16 at 16:18