How to Fit A Straight Staircase?

Embarking on the journey of fitting a straight staircase can be a rewarding but intricate task. In this staircase installation guide, we’ll unravel the step-by-step process to make this seemingly daunting endeavor more manageable.

From crucial measurements to precise installations, we’ll explore the key elements that contribute to a seamlessly fitted straight staircase.

Whether you’re a seasoned DIY enthusiast or a first-time home improver, this article aims to provide you with clear insights and practical tips for successfully fitting a straight staircase in your living space. So, let’s dive into the fundamentals and transform your vision into a well-fitted reality.

Related: What Is A Floating Stairwell?

Table of Contents

Staircase installation guide for fitting a straight staircase

It is neither a straightforward task nor a walk in the park; rather, it tends to be a slow, laborious process that requires meticulous attention to detail. This is a two-person job, especially if you are installing a spiral staircase that may require lumber (3×2 or 4×2) for support. Scaffolding boards and some steps also came in handy.

When you arrive on-site to install your stairs, you must first measure the height of the floor and stairs. Sometimes, taking precise measurements using a level becomes crucial. This method involves using a carpenter’s level to evenly measure the surface, ensuring it is flat and level.

Alternatively, you can draw a straight line around the stairwell wall, acting as your reference point. Then measure the height of each pedal and multiply it by the number of pedals. Even if you can estimate the height of your stairs, make sure to measure accordingly. If the heights are different from floor to floor, it’s not straight.

Main measurements

The photo above shows what you need to check before installing the stairs (for stairs with a curve at the top). Dimension A is the length of the atrium and stairs.  And dimension B is the width of the stairs and, in the example on this page, determines how many posts you need to cut out when notching with a trimmer. Then, dimension C is the finished flooring.


How to install stairs

Step 1:

The staircase installed in these photos is a double helix staircase, and the staircase installation guide almost always starts at the top. First, drill and countersink the nozzle to prepare it to screw into the trimmer. Next, measure from the trimmer to the opposite wall (if you have one). This measurement will determine how much notch you need to make in the center post under the front end. Use a spirit level to measure the opposite side of the mixing rope. Next, cut the top spindle around the stair leaf/beam

george newelnotchedfortrimmer

Step 2:

All you have to do is (if the nosing is the same thickness as the floor) measure the height of the trim joist and transfer it to the newel starting from the underside of the nosing. Measure horizontally from the wall opposite the trimmer to get the stairwell width. Then know the distance from the end of the wall of the stair to the post to measure to determine the depth of the notch. In this case it must be taken directly to the back of the riser, the stairs are very tight.


george newelroundtrimm

Step 3:

Once grooved, the top of the stairs can be lifted into place and screwed through the (pre-drilled) nosing edge. It’s light enough to stay in place while someone measures the struts underneath. If you are supporting another staircase or finished floor, put down some lumber first to spread the load of the supports.


Step 4:

When the supports are in place and bearing all the weight, check that they are level before attaching the rope to the wall. For masonry walls use very strong masonry anchor bolts drilled from the invisible bottom. For a wood stud wall, secure it to the vertical studs with large wood screws, two per stud if possible.

Once it’s securely in place, it’s time to feed the next section and support it in place (let it dry to check it will fit before removing and applying a generous amount of wood glue). Apply a generous amount of glue to the mortise/tenon and the back and sides of the tread where it meets the riser and string.

george stairsmiddlein

Step 5:

The mortise and tenon are held together with pull pins. The carpenter building the stairs will drill holes in the posts and a slightly offset hole in the tenon so that when the dowel goes through it will pull the tenon tight into the mortise, closing any gaps between the post and the shoulder.

It’s important to sharpen the dowels like a pencil (or even sharper as shown in the photo below) so that they can fit through the offset hole in the tenon and exit the other side of the post without breaking or splitting anything. Put a generous amount of glue in the hole before hitting the dowel with a wooden mallet.

george dowelssharpened

Be very careful not to scratch the newel post when cutting out the pins. Leave them a little longer and clean them with a block plane.

Fitting treads and risers

The bottom section goes in last and is exactly the same as the middle section. When the staircase arrives on site, most of the treads and risers have already been installed. The rest of the treads need to be cut to size to install on-site, and the risers usually need to be cut to length. Installing Riser In some cases, it is necessary to install the riser as you go, and the same goes for the treads. Otherwise, they can get in last. When cutting the risers for the kite/spinner pedals, you will want to cut the sides at an angle so that the edges of the faces fit snugly into the risers.


In conclusion, fitting a straight staircase demands careful planning and attention to detail. By following the outlined staircase installation guide, you can transform a seemingly complex task into a manageable project. Remember, precision in measurements, thoughtful installations, and adherence to safety protocols are key.

This guide aimed to simplify the process, making it accessible to all. Now equipped with the knowledge to fit a straight staircase, you can elevate the aesthetic and functionality of your living space. So, embark on this home improvement journey confidently, and may your fitted staircase be a testament to your craftsmanship.

If you want to know more product details, contact us now!

Recent Blogs
Is the project about to start?

Get in Touch