Constructing concrete winder stairs presents a unique set of challenges compared to standard straight run steps. The converging angles and complex formwork require precise planning before any concrete is poured. By approaching the formwork strategically and understanding how to reverse engineer the final design, builders can create strong, visually appealing winder steps that meet modern building codes.
Reverse Engineering The Formwork
The most effective way to approach concrete stair forms is to visualize the finished product and work backward. Winder steps feature treads that are narrower on one side and wider on the other, creating a turning radius. When cutting the framing lumber, standard circular saws can struggle with extreme miter cuts. Instead of attempting highly complicated compound angles, adjust the form design to utilize simpler butt joints or shallower miters. These intersections can be easily secured using standard construction screws or duplex nails, which are essential for allowing the forms to be stripped smoothly once the concrete has cured.
Protecting The Foundation And Managing Gaps
When pouring exterior concrete steps directly against an existing structure, managing the space between the concrete and the home is critical. Using standard inch and a half thick framing lumber against the house will leave an unacceptably large gap when removed.
To keep the concrete as tight to the building as possible, builders can utilize a much thinner material, such as a quarter inch board, placed against the existing wall. Always install a piece of metal flashing behind this thin board to protect the foundation and wood framing from moisture damage during the pour.
Navigating Building Codes For Winder Treads
Before staking forms into the ground, it is imperative to verify the design against local residential codes. Many municipalities have adopted stricter regulations regarding the minimum width of winder treads. Modern International Residential Code standards mandate a minimum tread depth of six inches at the narrowest point of the winder step. Designing a form with steps that pinch down to a sharp point on the inside edge will result in a code violation and a potential tripping hazard. Always confirm dimensions with the local building department to ensure compliance.
Cutting Angles And Assembling The Boards
Precision is paramount when cutting the lumber for winder forms. A standard three step winder often utilizes a combination of common framing angles, such as 22.5 degrees, 30 degrees, 37.5 degrees, and 45 degrees, depending on the specific turning radius. Builders can assemble complex corners by combining two 22.5 degree cuts to create a clean 45 degree turn. For challenging layouts, assembling the individual step forms in a spacious area, like a garage or driveway, before carrying them to the final location can significantly simplify the installation process.
Three Key Construction Tips
Use duplex nails or exterior screws to fasten form intersections to make stripping the lumber easier and prevent damage to the newly cured concrete.
Avoid leaving large voids against the foundation by using a quarter inch board with metal shielding instead of standard dimensional lumber at the wall intersection.
Never allow winder treads to converge to a sharp point, ensuring the inside edge maintains a minimum depth of six inches to comply with standard residential codes.
Bonus Questions And Answers
Question: What Is The Recommended Subbase Preparation Before Pouring The Concrete Winder Stairs?
Answer: Securing the formwork is only half the battle, as establishing a proper base is essential for a successful installation. All topsoil and organic material must be removed and replaced with a layer of compacted gravel or crushed stone. This provides a stable, draining subbase that prevents the heavy concrete structure from settling unevenly over time, which would otherwise distort the carefully formed winder angles.
Question: How Can Water Damage Be Prevented At The Cold Joint Between The New Stairs And The House?
Answer: After the concrete has cured and the protective foundation forms are removed, preventing future moisture intrusion becomes a top maintenance priority. A high quality exterior polyurethane concrete sealant should be applied along the perimeter where the steps meet the wall. This elastic sealant bridges the tiny gap left behind by the form boards, flexing with seasonal temperature changes while stopping water from penetrating and eroding the foundation.
Question: Why Shouldn't Exterior Concrete Steps Be Doweled Directly Into A Home Foundation?
Answer: While prioritizing structural stability might tempt builders to tie the new stairs directly to the house, this can actually compromise structural safety. Exterior stairs and house foundations bear entirely different loads and are subject to different rates of soil settlement. If the heavy concrete steps are rigidly pinned to the wall with rebar, any downward settling of the stairs can exert immense pressure on the foundation, potentially tearing concrete from the structural base. It is much safer to use an isolation joint that allows the steps to move independently.
