A Note:

A fully tested Traditional House includes an attached 3 car garage, outdoor pool, L-shaped stairs, walkout basement, (wet sports bar, workout room, bathrooms, home office, theater room, game room), 11 bdrs, 14 ba, 2 level sunrooms, drafting room, home office, kitchen/nook, family/formal dining room, laundry room, and enclosed decks, grill/playground area.

• Customize The Sims™ 3 with official items. Browse and shop for all your favorite Stairs items.
• A guide to creating U-Shaped stairs with the modular kit, that requires Open for Business, but uses no special cheats. What you will need. Open for Business Stair Behaviour when making split level staircases (by Jonesi) MikeInside's Modular-Stairs Tutorial (by MikeInside) Tutorial. Easy U-Shaped Modular Stairs. Originally posted.
• Instead of doing U shaped modular stairs, you can make L shaped modular stairs by doing all the steps above but replacing the L shaped frieze with a basic 1x2 frieze. You must do a 1x2 frieze. Although you can place modular stairs on a 1x1 frieze, it won't work in-game. Also, it looks stupid.
• STAIRCASE SHAPES An Architect Explains. An Architect has described the different shapes of staircases, Straight, with Landing, L-Shaped, U-Shaped, Winder, Curved, Circular, Spiral, Elliptical. Sims 4 Mods Sims 3 Houses Ideas Sims Ideas House Ideas Sims 3 Cc Finds Sims 4 Bedroom Sims 4 Clutter Sims Building Sims 4 Cc.

Sims 3 Grand Staircase

As far as I know, there is no cheat to make it so friezes can be placed on ground floors. For that, you should probably just do the traditional way to making modular stairs. Also, these stairs will not be equal length, so if you suffer from video game symmetry OCD, avoid this tutorial!
Friezes are a feature in Ambitions that allows you to place foundation height walls on top of normal height walls without having to go through the 'constrainfloorelevation' cheat. They are acessed through a cheat called 'placefriezes on/off.' Friezes are created by going into the foundation menu, clicking the traditional brick foundation and dragging it across an upper level with a floor. Friezes cannot be placed next to walls unless you used the 'constrainfloorelevation' cheat.
Games Needed:
Ambitions
Cheats Used:
placefriezes on/of
constrainfloorelevation false/true
Step 1
Create the shape of your house and plan where you want you rooms and stairs to be.

Choose your stairs and place it in the flat section of the L.
Step 6
Open the cheat menu again and type 'constrainfloorelevation false' (remember to open the cheat menu again when you're done, hit the up key and replace false with true.) Choose your stairs again and place them by holding the stairs close to the third floor.
Other Shapes
Instead of doing U shaped modular stairs, you can make L shaped modular stairs by doing all the steps above but replacing the L shaped frieze with a basic 1x2 frieze.
You must do a 1x2 frieze. Although you can place modular stairs on a 1x1 frieze, it won't work in-game. Also, it looks stupid.


A Note: As far as I know, there is no cheat to make it so friezes can be placed on ground floors. For that, you should probably just do the traditional way to making modular stairs. Also, these stairs will not be equal length, so if you suffer from video game symmetry OCD, avoid this tutorial!
Friezes are a feature in Ambitions that allows you to place foundation height walls on top of normal height walls without having to go through the 'constrainfloorelevation' cheat. They are acessed through a cheat called 'placefriezes on/off.' Friezes are created by going into the foundation menu, clicking the traditional brick foundation and dragging it across an upper level with a floor. Friezes cannot be placed next to walls unless you used the 'constrainfloorelevation' cheat.
Games Needed:
Ambitions
Cheats Used:
placefriezes on/of
constrainfloorelevation false/true
Step 1
Create the shape of your house and plan where you want you rooms and stairs to be.

Choose your stairs and place it in the flat section of the L.
Step 6
Open the cheat menu again and type 'constrainfloorelevation false' (remember to open the cheat menu again when you're done, hit the up key and replace false with true.) Choose your stairs again and place them by holding the stairs close to the third floor.
Other Shapes
Instead of doing U shaped modular stairs, you can make L shaped modular stairs by doing all the steps above but replacing the L shaped frieze with a basic 1x2 frieze.
You must do a 1x2 frieze. Although you can place modular stairs on a 1x1 frieze, it won't work in-game. Also, it looks stupid.

U Shaped Stairs Sims 4

Sims 3 U-shaped Stairs Tutorial

Sims 3 U Shaped Stairs