Building a Staircase: Design

The next stage of the project is to build the staircase that will lead up to our new 2nd floor (the loft). The loft was framed out over a two periods: just before we started the roof and just before we moved in; it sits over the bedroom, bathroom and kitchen.

Cut-away view from digital 3D model (used during design phase) showing how the new staircase leads up-to 2nd floor loft

Developed during our design phase back in the summer of 2010 (!), the staircase will consist of 3 parts:

• The first flight of stairs starts at the edge of the bedroom door (where the floor was extended) and runs up to a landing . This will be an "open riser" stair, meaning the vertical elements of the stair (known as risers) are gone. Because the stair sits over the entrance to our terrace (with glass doors), we did not want to block the light, so not having a risers will allow light to pass through the staircase.
• The second part is the landing, which is bolted into the exterior brick wall (just above the door to the terrace).
• The final part is the 2nd flight of stairs, which is turned 90 degrees and starts at the edge of the landing and goes up to the loft. Because everything is so tight, this second flight will pass through the bedroom after passing through the structural wall opening that was framed out yesterday.

While the design intent was established long ago, I only developed the actual detailed design of how it will be built over the last few weeks. These drawings were initially done by hand - once they were finished, I submitted them to Building Control (the London version of NYC's Building Department). After a few minor revisions, Building Control approved the design for structural integrity and deemed it compliance with the UK Building Regulations (similar to NYC's "Building Code").

3D hand sketch showing the structural elements of the staircase

This approved design details how the landing becomes a structural element that will be bolted into the brick wall on one side and fastened to the structural stud wall on the other. Because the first flight of the stair has no risers,  each tread (the horizontal "step") is notched into a large 2"x8" structural stringer (the diagonal element) on each side. This will make the flight incredibly strong while still allowing light to pass through. This flight is then attached to the landing using heavy screws and steel plates.

Section sketch showing the primary stringer and steel plate that assists in the connection to the landing.

One of the design ideas that made the stair more difficult to build was the idea of keeping the 1st flight a few inches away from the wall. The idea is to allow light to pass through this gap - both from the terrace door, but also from a light cove that will eventually built above (in the ceiling at the edge of the 2nd floor) - allowing the light to pass through should not only provide additional lighting for the stair, but should also create a great looking effect as the light washes down the wall.

From a structural perspective this mean that this 1st flight could only be held at the top and bottom, not also on the sides, as with most stairs. Because the landing is itself partially cantilevered, this meant that only through the combination of both landing and stair would the entire assembly actually be strong enough. This was achieved by allowing the primary stringer to be attached to the side of the landing using an additional piece of 2"x8" wood (creating a heavy angled "L" shape) that's stiffened by a heavy steel plate at the joint. This angled "L" shape will act almost like a column to hold the hanging end of the landing - this can best be seen in the section sketch (above) and plan sketch (below).

While everything looks good on paper, we'll soon see how it well it works in reality...

Plan view of landing and how 1st flight of stairs is fastened to it.

Rebuiding "The Box"

With the structural wall re-framed and the floor extended, the entry and walls to the bedroom are mostly framed out and we're almost ready to have the plasterboard (called Sheetrock in the US) replace the temporary plywood walls. It's because of these plywood walls that we call the bedroom "the Box" - since we moved in, the "bedroom" has been enclosed by plywood, making it look like a "box". But today...that's going to change!

The re-framed structural wall and extended floor in-front of "the Box"

The first thing that needs to be done is some additional minor re-framing of the structural wall (also one of the bedroom walls) to create an opening where the new staircase will pass as it goes upto the loft (2nd floor). This work was left until today because in order to do it, I'll need to remove all the plywood. Taking down the plywood was technically easy to do, but psychologically, this is a very big deal for us - we've been living with it for over a year, and this is the first step to returning to some level of normalcy.

Temporary plywood walls of "the Box" (photo on the left) - a few minutes later, the first few panels removed (on the right)

All the temporary plywood removed from the re-framed structural wall along the bedroom

With the plywood removed, I was able to easily cut out the opening and set a new wall-plate that will act as a structural anchor for the new staircase. This completed all the re-framing work and I could now begin re-sheathing the walls.

Cutting out studs to make an opening for the staircase

The completed opening

 The re-sheathing of the bedroom began with adding plywood - but this time it's permanently attached to the exterior face of the structural wall. This plywood is being required by our official from Building Control (the equivalent of the Department of Buildings in NYC) to make the wall extra strong and stiff so that it acts as what's known structurally as a diaphragm system. The entire wall is sheathed in structural plywood and fastened every few inches with screws. Later, this will be covered with plasterboard and painted - eventually it will be blended in and hidden.

The first piece of structural plywood added

A few more pieces of plywood seen from inside the bedroom. The opening for the staircase is on the right side

The completed plywood seen from outside the bedroom - the door opening is again visible.

Once the plywood was completed, I shifted my attention to the other walls so as to hang the plasterboard. Before any plasterboard could be hung, the wall that separates the kitchen from the bedroom needed to have the final studs installed. These were quickly cut, placed and leveled.

The remaining studs installed at the side bedroom wall

Once the studs were in place, it was finally time to start hanging the plasterboard. I hung one board on the side wall just to see how everything fit together, and then quickly insulated the structural wall before covering it with plasterboard. All the walls will be insulated to help with sound dampening and to retain heat within the bedroom during the winter.

The first piece of plasterboard in the bedroom!

Insulating the structural wall.

Hanging plasterboard is quite not as basic as it sounds. Building control requires us to maintain a 1 hour fire rating around the bedroom, which can be achieved with either 2 layers of regular 12.5mm (5/8") plasterboard or one layer of special fire-rated plasterboard - which in the UK is, funnily, colored pink (to make it obvious the board is rated). Here I decided to use the pink (rated) plasterboard along the structural wall (because it won't have much traffic/abuse) but two layers of regular board on all the other walls (so they are stronger and can take more abuse & traffic).

A few more boards up - the pink (fire-rated) plasterboard on the front wall with regular board on the side wall.

Most of the plasterboard hung

The plasterboard went up rather quickly - but by this point it was late, and I was getting tired after a 12-hour day of labor. But the plasterboard made a huge difference in how the room felt - the plywood is gone, and our bedroom is finally starting to feel like a real room rather than a plywood box!

End of the day - the bedroom re-sheathed in plasterboard