The other day a friend was complaining about his latest project – installing new stair treads on a flight of stairs in his house. One of his main gripes was that he couldn’t find a stair tread that would fit the current dimensions of his stairs and that there were too many different sizes. That made us wonder – what is the standard stair tread thickness?
Standard stair tread thickness is from 1” to 1 1/16”. There is no standard thickness for stairs that do not have a riser, which can range from ⅜” to 2” and more – it depends on the width of the riser. Stair treads without risers are typically thicker than treads with risers.
Due to differences in materials and lumber type, there cannot be a mandatory thickness for stair risers. Oak – a traditional stair riser material – is just one of a wide variety of woods used for stair risers. Since different materials have different strengths, no one thickness is mandated.
Below we’ll take a look at the reasons a standard stair tread thickness exists, as well as the differences between stair tread riser thickness when there is and is not a riser. Finally, we’ll go over the different stair tread materials and how the thickness might vary depending on which type of material you use.
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What is the Standard Thickness of a Stair Tread?
The standard thickness of stair tread is up to 1-1/16” of an inch, although 1” stair treads are extremely common and found at all big box home reno stores. Remember also that stairs must have a minimum depth of 10” and minimum width of 24”.
Many stores offer treads that are ¾” thick. How is that possible if they are not up to code? The minimum thickness is based on tread nosing requirements. In many jurisdictions, stair treads must have a ½” nosing radius. That means the thickness of that tread is 1” since two times the radius is 1”.
However, you’ll notice that many treads sold in stores have a nosing that is thicker than the tread so that the nosing itself fits above and also over the riser beneath it. This allows tread manufacturers to make treads of a smaller thickness while still adhering to code for nosing specifications. If you have plywood or another material beneath the tread, then the tread thickness code is still met.
Therefore, you’ll also find that ¾” treads are widely available for purchase – they will have a nosing that is thicker than the actual tread, but it will overlap the top of the riser. This is only allowed if there is plywood or another solid material beneath the tread to combine to make the tread over an inch thick.
This standard thickness is for stairs with risers. For stairs without risers, the minimum standard thickness is 1 ½”. Stairs without risers do not have a maximum thickness but would have to fall within the range of the rise/run of the stairs. For instance, if a flight of riser-less stairs had a rise/run of 7.5/11, then obviously your stair tread thickness should be less than 7.5”.
While stair treads can come in a variety of material types, code does not discern between them. Therefore a riserless stair tread must be a minimum of 1 ½” regardless of whether it is pine or ash or some type of composite material.
Building Code for Stair Tread Thickness
Code for stair tread thickness for stairs with risers can be confusing, primarily because there is no established minimum thickness for stair treads. Due to material differences and the tendency of stair treads to be layered – i.e., solid lumber on top of plywood or a similar base – there are too many variables to state a specific tread thickness.
However, a stair tread on top of a riser can have a maximum thickness. How? Well, the radius of a stair tread nosing can only be up to 9/16”. If you double that to get the diameter, then you have 1 ⅛”. It would be impossible to have a stair tread that was thicker than 1 ⅛” on top of the riser while maintaining the maximum acceptable nosing radius of 9/16”.
If the stair tread has a depth of 11” or more, a nosing is not required. Therefore, the tread can be as thick as you’d like, as long as the riser plus the thickness of the tread adhere to total stair riser height requirements.
A riserless stair has a minimum thickness of 1 ½”. These treads are typically made with one type of material, such as standard dimensional lumber, which has the minimum thickness required. There is no maximum thickness for a riserless tread as long as it does not exceed the maximum stair rise height.
Lastly, code stipulates that a nosing cannot extend beyond 1 1/4” beyond the riser beneath it. The minimum it can extend is ¾”.
Type of Wood to Use for Stair Treads
You can use any wood for a stair tread. If you look at your local home reno big box store as an example, you’ll find oak and softwoods such as pine to be the most common type of pre-fabricated tread available.
While oak is the most common and very hard, softwood such as pine will suffice as long as the appropriate number of stringers are used to support the treads. However, if you plan on subjecting your stairs to significant weight strain – such as moving heavy appliances or objects like a piano – then clearly a softwood would not be a good choice to retrofit your existing stair treads.
Higher-end stair treads made from ash or simply using plywood with a carpet or vinyl over the top are excellent and extremely strong choices for a stair tread. While ash or hickory may are premium products and more expensive, plywood treads are cheap and just as durable.
Plywood Thickness for Stair Treads
Plywood is one of the most common stair tread materials, although you often don’t see it because it is covered by carpet, vinyl, or another type of floorings such as laminate or hardwood.
While you could finish your steps with plywood, this isn’t a common solution since the end grain of the plywood would need a nosing and, aesthetically, no one wants the end grain of plywood visible. However, once covered in carpet or vinyl, plywood steps function just as any other type of tread material.
As well, plywood must adhere to the same thickness standards as traditional lumber. That potentially means you’ll need either a very thick plywood, which is expensive or double up on ½” thick plywood to achieve a thickness that will be suitable for your stairs. Carpet or vinyl does not count when calculating tread thickness, as they have no load-bearing capability and are entirely aesthetic.
Lastly, plywood is often the material beneath a finished pre-fabricated tread, such as an oak or pine tread. This allows for the finished tread to be thinner and, thus, cheaper. Using the plywood to make up some or most of the tread thickness could result in cost savings for your finished treads, which could then allow you to purchase a more expensive tread.
Stair Tread Thickness for Wood Alternatives
Laminate flooring is often a choice for stair treads, and many laminate manufacturers offer nosing pieces to be used with their product when used in stair applications.
It should be noted that laminate does not come in thicknesses greater than ½”. Since treads should be thicker than ½” – especially laminate treads – you’ll need a plywood tread beneath the laminate.
Engineered hardwood and traditional hardwood flooring are thicker than laminate – up to ¾” thickness or more – and have special nosing pieces for stairs. However, installing engineered or standard hardwood requires nails and, thus, a solid backing beneath. So you’ll need plywood beneath this type of material as well on a stair tread.
Floating Stair Tread Thickness
Floating stairs have no immediate connection between the stair above or below it. They are often cantilevered individually from walls or from a center column.
Stair treads on floating staircases must abide by the same rules as traditional staircases – but since there are no risers, the tread thickness can vary and you might find thicknesses up to 4”. code dictates that treads on floating stairs cannot be less than 1 ½” thick – without exception.
How Do I Make Stair Treads Thicker?
If you are concerned about your stair treads – that they may be too thin – you can go over the top of them, but then you’ll need to redo your risers and your rise may be too high.
It’s better to remove the thin treads and replace them with thicker ones. You will still increase the height but hopefully not too much where you’ll have to replace the stairs altogether.
Replacing stair treads for aesthetic reasons is a great idea, as stair treads can add tremendous value to space and can be quite stunning. However, consider that doing so may result in an entire teardown of your stairs or a top or bottom step that is shorter, higher, or lower than the rest.
If making your stair treads thicker only adds ¼” or less to your stairs, then you’ll likely be able to get away without any noticeable walkability issues on the stairs. But adding any more height could make the stairs fall out of code, and also be a safety hazard.
It may be best to retrofit with a similar thickness but a stronger material. Consider harder woods or plywood with a covering to replace your old treads before you decide to replace the entire stair assembly.
Conclusion
While stair thickness might seem like an irrelevant measurement when all other factors are considered, it is still a safety issue. The slightest alteration in stair thickness can cause a trip, fall, and serious injury. Following code to the best of your ability is the best way to avoid any accidents.
Remember that no matter which type of stair tread you choose, be sure to include the thickness of it when calculating the total rise of your stairs if you are building them yourself. The planning phase of your stairs should include the exact type of riser and tread so that you can accurately determine the specs of your stairs.
Thanks again for taking the time to read this article. I hope it provided a bit more clarity when it comes to stair tread thickness. If you have any other questions, comments or concerns, please drop me a line or comment below – and best of luck on your next stair project!