# Stair Design Weekend Cabin Retreat Project

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Stair Design Weekend Cabin Retreat Project
Sacramento City College EDT 51 Kenneth Fitzpatrick, P.E. EDT 51-Stair Design

Objectives Define common stair terminology.
Discuss the appropriate use of various stair designs. Design a stairway for a residential structure. Draw structural details for a main stairs. Perform stair calculations for a residential stairway. EDT 51-Stair Design

Definitions A stairway is a series of steps with or without landings or platforms which is installed between two or more floors of a building. A house may have main stairs and service stairs. Main stairs are generally of much better quality than service stairs EDT 51-Stair Design

Definitions Six general types of stairs Straight run L Stairs
Double-L stairs U Stairs Winder stairs Spiral stairs Circular stairs EDT 51-Stair Design

Straight Run Stairs Most common type used in residential construction.
Straight run stairs, obviously have no turns. Least costly type. Require a long open space in which to construct. This may be difficult to accommodate in the floor plan EDT 51-Stair Design

Straight Run Stairs EDT 51-Stair Design

L Stairs Have one landing at some point along the flight of steps.
If the landing is near the top or the bottom of the stairs, they are called a long L stair. These stairs are used when the space required for a straight run stair is not available. EDT 51-Stair Design

L Stairs EDT 51-Stair Design

Long L Stairs EDT 51-Stair Design

Double L Stairs These stairs require two 90o turns along the flight.
Used when insufficient room exists for a straight run stair or an L stair. Double L stairs are not frequently used in residential construction. They are expensive to build and break up the floor plan. EDT 51-Stair Design

Double L Stairs EDT 51-Stair Design

U Stairs Can be constructed as either wide U or narrow U stairs
Both have two flights of steps parallel to each other with a landing between. The difference between the wide and narrow U is the space between the flights. Narrow U stairs have little or no space between the flights; wide U have a well between the flights EDT 51-Stair Design

U Stairs EDT 51-Stair Design

U Stairs EDT 51-Stair Design

Winder Stairs Have “pie-shaped” steps which are substituted for a landing. Used when space is insufficient for an L shape. The triangular shaped steps should be as wide as a standard step. Are not very safe. EDT 51-Stair Design

Winder Stairs EDT 51-Stair Design

Spiral Stairs Used when little space is available.
Most are made from steel and welded together. Not very safe; have wider steps. EDT 51-Stair Design

Spiral Stairs EDT 51-Stair Design

Spiral Stairs EDT 51-Stair Design

Circular Stairs EDT 51-Stair Design

Circular Stairs EDT 51-Stair Design

Stair Terminology Baluster: vertical members that support the handrail on open stairs. Bullnose: the first step on an open stair, which has been extended out forming a semicircle and often receiving the newel post. EDT 51-Stair Design

Stair Terminology Carriage: the rough structural support (usually 2" x 12") for treads and for risers of wood stairs, sometimes called string or stringer that has been routed or grooved to receive the treads and risers EDT 51-Stair Design

Stair Terminology Enclosed stairs: stairs that have a wall on both sides (also known as closed, housed, or box stairs) Headroom: the shortest clear vertical distance measured between the nosing of the treads and the ceiling. Housed stringer: a stringer that has been routed or grooved to receive the treads and risers EDT 51-Stair Design

EDT 51-Stair Design

Stair Terminology Landing: the floor area at either end of the stairs and possibly at some point between, as in the case of L stairs. Newel: the main posts of the handrail at the top, bottom or at points where the stairs change direction. Nosing: the rounded projection of the tread which extends past the face of the riser. EDT 51-Stair Design

EDT 51-Stair Design

Stair Terminology Open Stairs: stairs that have no wall on one or both sides. Plain stringer: a stringer that has been cut or notched to fit the profile of the stairs. Rise: the distance from the top surface of one tread to the same position on the next tread. Riser: the vertical face of a step. Run: the distance from the face of one riser to the face of the next. EDT 51-Stair Design

EDT 51-Stair Design

EDT 51-Stair Design

Stair Terminology Stringer: a structural member, also called the carriage that supports the treads and risers. Total rise: the total floor-to-floor vertical height of the stairs. Total run: the total horizontal length of the stairs. Tread: the horizontal member of each step. EDT 51-Stair Design

Stringer Types EDT 51-Stair Design

Proper Stair Design Means
The stairs will support the required weight The stairs are wide enough to provide ease of passage and movement of furniture. The stairs slope between 30 and 35 degrees. The stairs are not less than 3’-0” wide. EDT 51-Stair Design

Stringer Design The main supporting members of the stairs are the stringers. Plain stringers and housed stringers are the two types. EDT 51-Stair Design

Plain Stringers Are generally cut from 2 x 12 straight-grain fir.
Treads and risers are nailed directly to the stringers. This type of construction is generally used for service stairs and occasionally for main stairs if they will be carpeted. Are sturdy, but tend to squeak. Do not look “finished” Treads are 2” fir; risers are 1” white pine EDT 51-Stair Design

Housed Stringers Constructed from finished lumber
Generally purchase pre-cut or pre-assembled May, however, be cut from 1 x 12 or 2 x 12 lumber 1/2” deep grooves are usually routed in the stringers to hold the treads. The bottom and back sides of the grooves are wider than the thickness of the treads and risers so wedges may be driven in to hold them in place EDT 51-Stair Design

EDT 51-Stair Design

Housed Stringers The treads, risers and wedges are glued and nailed into place. EDT 51-Stair Design

Stringers EDT 51-Stair Design

Other Stair Components
A stairway must provide a handrail for support while ascending and descending the stairs. One rail is sufficient unless the stairs are very wide Handrail height should be between 30 and 34 inches. Note that the height is greater at a landing than along the incline. EDT 51-Stair Design

Handrails EDT 51-Stair Design

Other Stair Components
Standard Treads 1-1/4” thick oak 10-1/2” wide 11-1/2” wide A tread width of 10” is the most popular choice. Risers the ideal riser height is between 7” and 7-1/2”. Are usually 3/4” thick. Usually made of clear white pine. EDT 51-Stair Design

Treads and Risers Every step must be the same size and proportion
EDT 51-Stair Design

Rules for Stair Design Rule #1: the slope of the stairs should be between 30 and 35 degrees. Rule #2: The sum of two risers and one tread should equal 25 inches. Rule #3: the product of the riser height multiplied by the tread width should equal approximately 75 inches. Rule #4: the sum of one riser and one tread should equal 17 to 18 inches. EDT 51-Stair Design

Stair Calculations - Step 1
Determine the distance from finished floor to finished floor. This is the total rise of the stairs. Add the distance from the finished lower floor to finished ceiling, the thickness of the ceiling material width of the floor joists thickness of the subfloor and finished floor. EDT 51-Stair Design

Stair Calculations - Step 1
Finished lower floor to 8’-0” finished ceiling The thickness of 1/2” the ceiling material Width of the floor joists 9-1/4 Thickness of the subfloor 1/2” and finished floor. Total 8’-11 1/4” Convert total to inches = 107 1/4” EDT 51-Stair Design

EDT 51-Stair Design

Stair Calculations - Step 2
Determine how many risers will be required First, divide the total rise by 7 7 is an ideal riser height and is the logical place to start. 107 1/4” / 7 = risers The number of risers must be an exact number, so 15 or 16 risers will be required. 107 1/4” / 15 = 7.15 inches; use this height Remember: each riser must be exactly the same height ! EDT 51-Stair Design

EDT 51-Stair Design

Stair Calculations - Step 3
Determine the tread size and total run which will yield a stair slope between 30 and 35 degrees. Remember, there is always one less tread than the number of risers. The floor serves as the top tread. Using Rule #2, the sum of two risers and one tread equals 24.80” This is very close to the required sum of 25. This indicates this combination will be acceptable. EDT 51-Stair Design

EDT 51-Stair Design

Stair Calculations - Step 3
For comparison, use Rules #3 and #4 #3: the product of the riser height and tread width should be approximately 75 inches. 7.15 x 10.5 = 75.1 #4: the sum of one riser and one tread should equal 17 to 18 inches. 7.15” /2” = 17.65” EDT 51-Stair Design

Stair Calculations - Step 4
Darken the tread and riser lines Draw the bottom edge of the stringer Locate stairwell rough opening size. This dimension is determined with the headroom dimension. EDT 51-Stair Design

EDT 51-Stair Design

Stair Calculations - Step 5
Remove construction lines and add notes. EDT 51-Stair Design

EDT 51-Stair Design

EDT 51-Stair Design