The use of wedges in stair construction is commonplace in many countries but mainly those with an Anglo-Saxon heritage like the UK, US and Canada.

A key goal in stair building is to create a staircase that fits together firmly, and that is resistant to the effects of wood contraction over time. In particular, it’s important to find a way to stop the steps and risers from coming out of the stringboards.

An alternative to wedges

One solution is to use a little screw positioned at an angle through the step into the stringer, but it does have limitations. You would normally slide the steps and risers into one string from the side, then add the second string again from the side. If you are constructing a stair between two walls, this isn’t possible on site so the stair would need to be assembled in the workshop first.

The benefits of using wedges

So instead we can use wedges.

The step and riser housing in the stringboards is extended to the back edge. The steps and risers can then be slid into place from behind, and hammered and glued into place for a very strong and tight fit. The wedges are hidden behind the stairs out of sight, and the housing does not have to be so precise, the wedging process itself will ensure a good fit.

Doing it this way allows you to assemble on site rather than transport and fit into position a pre assembled stair from the workshop.

If you would like a quick way to set up the manufacturing details for the wedges housing, as well as the rest of your stair design, this is possible using StairDesigner, which is a professional stair design software package.

How to apply wedges in StairDesigner

Watch this video to see the set up in StairDesigner.

The wedges feature is available within the 2D stair view.

With the Stringboard view selected, look in the Properties menu of the string and you’ll find a Wedges section.

Once activated, the housing is extended to the edge of the string and at an angle to make room for the wedge.

The angle can be adjusted. 4 degrees is normally sufficient but if you want to go higher you can. But the thinner or finer the wedge the better the holding power.

Wedges can be applied for both the steps and risers or just one of those as you prefer.

Once you’ve completed your stair design, you have immediate access to the cut list, full plans and CNC files to build it.

More information on StairDesigner

If you would like to test StairDesigner, please register for free on our website to download the free version.

This version includes all design features.

Please leave a comment or contact us here.


  1. zidane on October 9, 2023 at 8:34 am

    nice information and good article thank you

  2. online translate on September 7, 2023 at 10:02 pm

    I love this idea of using wedges in stair building! It makes the process so much easier and less time consuming.

  3. Adrian Scott on April 10, 2022 at 9:54 pm


    i had a look at stair designer i went to see some one with your software it was very good (designer only)i am thinking u would opt for the stair and cnc option.the cnc i have is a masterwood winner am i right in thinking match tool tables in stairdesgner and cnc tool tables.i can use dfx files to run the cnc if i change them to iso. do i need to think about post processor (no nothing about post processor)

    whats best computer spec to use for your software.(will be different computer than cnc )
    is desktop best or can i use a laptop as can then design at home.(whats the options when you purchase software to run both ?)

    i have looked at a few stairs on u tube being machined using your software.looking to see if the tennon on inner stringer thats fits into newel is there a tool path for above and then a tool path below tennon ? the stringer will be on pods and machine and tooling are able to carry out this operation.

    do i need to flip kites and treads to grove for riser and bulnose or is this done with in the program

    thanks in advance

    regards adrian

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