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.

The Shower: Waterproofing (part 1)

With the shower walls framed out and sheathed in plywood, the next step is to start waterproofing. I had to do a huge amount of research on the subject, but in the end I actually decided to layer several different waterproof systems over each other. It's definitely a bit of overkill, since each system is designed to function independently. But the memory of a leak from the flat's original, ancient loo early last year is still too close for comfort, so we decided not to take any chances and to go with the logic "better safe than sorry". (The leak was nothing to do with us, though of course we had to deal with the aftermath.). I thought about it afterwards and realised that the idea of redundant waterproofing is similar to what we have on our new slate roof - it has multiple layers of waterproofing to minimize the chances of any water leaking through.

For the initial layer, I had decided on using BAL's WP-1 tanking kit - a rubberized membrane that is painted on. It has the consistency of cream, but once dried, it becomes a flexible rubber membrane. This flexibility is ideal (and often necessary) for a wooden substrate, because wood has a tendency to expand/contract with heat/cold. Also, older buildings settle over time, and they shake slightly when a heavy truck drives by - if one does not allow for all of this movement, there will eventually be cracks - and water just loves to slip through them...

Before any waterproofing could start, there was (or course) something that had to be removed, because it was in the way. The end of our steel beam (that supports the post which supports the new mezzanine's structural steel beam) had to be trimmed so it did not stick out.

In the middle of cutting off the edge of the steel beam

The completed cut

The initial waterproofing system - BAL's WP-1 Tanking Kit

The tanking system involved several steps: the first requires you to prime the plywood; after 15-20 minutes you can start painting on the membrane. Joints between wood, as well as any holes, have to be covered with a polyester gauze tape that help span the opening; finally, an additional coat of the membrane is applied over the tape.

The primer applied to the sub-floor on the underside of the shower.

The membrane is applied to the floor and wraps up around the edges to create a waterproof enclosure - and to prevent any leaks through the floor (to the flat below) in case any water leaks from the shower.

You may have noticed that the waterproofing that's been done so far is located below the shower, not at the floor level of the shower. As part of the redundant waterproofing, we decided to fully waterproof the bathroom's floor - but because our shower floor is sitting 9" above the bathroom floor (because of the steel beam), that waterproofing extends under the shower. Because of the configuration, we will have two (hopefully) waterproof levels under the shower. This means that should any water leak from the shower or drain above, the odds of it leaking through the sub-floor - and through to the flat below - are extremely slim. This is definitely unconventional - and certainly overkill - but we really want to minimize the possibility of a leak.

The initial layer of waterproofing (blue-gray color) below the shower on the bathroom's sub-floor

The Shower: Initial Build-out

While the plumber was installing the radiators, I was able to start focusing my attention (finally) on the shower. It (along with the rest of the bathroom) is going to be completely new - when we did demolition we pulled out all the old fixtures, so for the moment, the bathroom is just an empty space except for the toilet and the boiler. So the entire shower enclosure has to built from scratch: framing, walls, floors, waterproofing, tiles and new plumbing...in other words, "the works".

I had previously installed the bathroom sub-floor, working out the initial layout when we had the boiler installed. During that period, the wall separating the shower from the boiler was put up - so when everything is finally done, that wall will become the front of the shower (where the shower head and valve go).

Morning of October 17th - the previously framed-out is visible on the left.

After clearing everything out - the starting point for the shower!

The first task will be to start installing the tile backer boards - I had done quite a bit of research on the various options and decided to go with a product made by Marmox - a waterproof, insulated cement board. Not only will this be the proper surface to which the tiles can be attached, but it can be used as part of a waterproof system for building showers - I liked that this product accomplished several things at the same time. The Marmox boards can either be screwed into framing, adhered to masonry with adhesive, or nailed in place with plastic "spankers". I opted for using the "spankers" and the adhesive due to the very uneven surfaces of both brick and plaster - this was similar to dry-lining plasterboard in the living room. The adhesive itself is waterproof, but it also adds strength to the installation which will be necessary if we use heavier stone tiles.

Applying adhesive to the wall and the back of the Marmox board

The first Marmox board installed

The design for the bathroom (and specifically the shower) ended up becoming quite complicated as there are many "spanners" in the works here. You may have noticed there's a large arch in the brick wall - this was only discovered during demolition as it was hidden behind the old walls. This arch resulted in a steel post going in to reinforce the steel beam - which (of course) pockets into the brick wall directly above the arch. This post ended up in the shower, and the post is sitting on a heavy steel beam to help distribute the forces and weight (or to be more precise, the point load) of the post across a few floor joists below. As a result, the floor of our shower will sit on-top of the steel beam. I also added a ledge that wraps around two sides of the bathroom - this was initially done to help hide the concealed cistern from our loo, but i carried the ledge around to give a ledge over the sink and in the shower where we can put things. The final design of the bathroom incorporates all these elements and (hopefully) will seamlessly tie everything together for a clean and simple appearance.

Second Marmox board installed and starting to frame out the base of the shower. The ledge is also starting to be framed on the right side of the picture

The shower base fully framed out - sitting on top of the steel beam.

The shower floor's plywood substrate

The Marmox system includes an insulated and waterproofed floor board that is pre-sloped for water drainage. I ordered one that was closest to the size of our shower and then cut it down to fit. One of the other things I liked about the Marmox system is that is has been designed around a specific drain - the floor board is pre-cut to receive the drain, so the entire system is integrated and should come together easily.

The Marmox floor board

We had worked out that as the plumber finished working on the heating, he would do the "roughing", or first fixing, of the shower pipes and fixtures. We had previously selected and ordered the shower head and valve, but that evening "Aglaya" and I had to choose exactly where they should be installed the following day - she really enjoyed this part!

Locating the shower valve - which height feels right?

Locating the shower head.

So the next day our plumber installed the pipes and fixtures based on the locations we selected the previous evening.

October 20th - Overall view of the shower plumbing

Detail view of the shower valve in the wall

The floor drain anticipating the future floor height due the steel beam (visible in the backgound). The white pipe is a condensate drain coming from the boiler

With the initial plumbing completed, it was finally time to sheath the shower with plywood, covering the pipes (on one side). As part of the waterproofing I decided to use WPBP (waterproof boil proof) plywood that would later be covered with a waterproof tanking kit (to be explained in the next post), followed by the Marmox board.

Installing the plywood substrate

Most of the plywood installed

With the floor, plywood, plumbing and Marmox in place...the outlines of a shower are finally starting to be visible!

Balcony Formwork

With the ridge tiles done, the roof is basically finished - so it's nice to finally start doing something else. The next area to focus on is finishing the dormer - but before working on the carpentry and painting which will be quite involved, I figure it makes to start at the bottom. The bottom of the dormer will be a narrow "Juliet" balcony which will sit in front of a very large series of windows that will open (on one side) like a set of French doors. The idea is that one day, we'll be able to open these doors and step out onto the balcony to enjoy a view if the beautiful neighboring gardens and trees below.

The Dormer -afternoon of June 22nd

The balcony will be made of concrete so that it's strong enough to allow the balcony to extend beyond the face of the brick wall, and also to help hold together all the loose bricks that remain exposed. The first step in working with concrete will be to make the wooden form-work that will hold the wet concrete in place before it dries.

Before starting the form-work, the first task was to remove some obstructions that were in the way - the ends of the vent stack for the plumbing, and the downspout for the old gutters. These were quickly cut away, revealing that some of the brickwork had been removed, leaving a gap. I soon realized that before moving forward, this gap had to be repaired before the form-work could go up - whoever installed these pipes really butchered the wall and the brick. Because it was so bad, the rest of the day was taken up by repairing and filling in this gap. It was only on the following day that I was able to do the actual form-work, and that ended-up taking the whole day...but at least it was finished. Another item to check off the list!

The obstructing pipes before being cut away

After the pipes were cut, the gap and damage to the brick (from when the pipes were originally installed) was revealed

To fully repair som eof the decorative brickwork would have involved removing most of the surrounding bricks, and possibly causing more damage. To avoid this, I decided to span the gap with a plate of unused steel from the structural work. The plate was held in place by mortar.

Brick were then laid over the steel plate and the gap was slowly filled.

The completed repair.

June 23rd - the form-work in place.

This space is where the concrete will go. The left side is the form-work, the right side is the wood "wall plate" that used to hold the original roof rafters.

The completed form-work

Roof Construction: Open Heart Surgery - Day 3

The roof is still half open to the elements so today we're hoping to finish the steel installation and start closing the roof up.

The first step is to install the final piece of steel at the hip rafter and splice it to the lower one. Once that's in, we're going to insert stained pieces of wood into the steel channel so we can easily fasten the rafters, rather than having to deal with steel. It's much easier and faster to screw wood together than having to deal with steel (am a bit fed-up with steel at this point). The other advantage of the stained wood infill, is that it will present a more finished look. Once we wood is in, we'll start setting the rafters back and if we're lucky we can start installing planks.

The morning - steel on one side of the hip rafter, but not the other.

Cutting the ends of the final piece

Bolting the last pieces of steel together

The last splice

The steel reinforcement completed

Installing the wood infill

First piece of stained wood installed

Installing the last piece of wood infill.

Setting the rafters

We ran into some trouble installing the rafters. While we were setting them, I had a sinking feeling that something was wrong...sure enough I soon realized that the rafters were not being installed in a straight line. That may sound easy --if you're just sitting behind a desk--but in reality the slightest difference will create a wavy surface for the planks and slates...definitely a problem. I again realized that I needed to use my knowledge of geometry (and desire for precision) to correct the problem.

Tomorrow we're going to have to unscrew most of the rafters and reset them using a string line and a long, flat piece of wood to double check we were getting a flat surface. The guys ended up getting annoyed at me when i made them stop to figure this out as it was dark and late, but unfortunately this is absolutely necessary.

The wavy rafter

Roof Construction: Open Heart Surgery - Day 2

Today we continued with our open heart surgery on the roof. It's Saturday so we are required to stop at 2pm today...a lot to do with limited time...

Yesterday we opened up the lower portion of the roof's corner and installed the bottom two steel channels. Today, we're opening up the rest of the roof which means that 1/2 of the entire roof will be open to the sky. These next few days will be the greatest exposure of the flat to the elements. Once the roof is open, we'll have to measure the remaining lengths for the top two steel pieces, cut the steel and install them to reinforce the hip rafter and splice them together.

This sounds much easier than it is--for starters we have only one shot to get the correct cuts in the steel and cannot make any mistakes. So we ended up cutting small bits a time to get the correct angles and geometry. We ended up going back and forth half a dozen times before it finally fit, but at least we got it. Because it took so much time to cut the one piece, we'll have to cut and install the final piece of steel on Monday.

Interior view in the morning

The upper half of the roof slates removed - you can now see through the roof!

The ends of the lower two pieces of steel

Interior montage - half of the roof open

Cutting ends of one of the upper steel pieces (this happened 6 times)

Finished end

Bringing the steel onto the bridge (this also happened 6 times)

Lifting it into place (this also happened 6 times)

Once the steel is correctly in place, tightening the splice (connection)

Fastening bolts at the splice

Looking out from the open roof

2pm - covered-up and finished for the day