MiniOffice

The soon-to-be office room just before beginning the project

Summary: This page documents building a small detached office in a former hallway bathroom in our family's Ljubljana apartment.

The office is located just across the hallway from the apartment; the basic form factor is a 2 m x 1 m rectangle (read: small!). The project involved running new electrical cable, installing outlets, refinished the walls, installing a light fixture, and sanding and refinishing the structural timbers, which were previously hidden behind a plaster coating.

Electrical

A freshly cut/excavated chase and conduit to supply outlets for a computer.

Initial status: When beginning the project, the room was supplied with a hot and a neutral line that powered a bare lightbulb hanging above the door. There were no outlets, and also no ground wire—the existing wiring predated current building practice where ground wires are run as a matter of course.

Summary of improvements:

Replacing the existing hot and neutral wires in the office with modern 3-wire VDE cable (that includes a ground wire!)
Installing outlets
Cutting chases in the masonry wall and run conduit and cable for outlets
Installing junction boxes
Installing a proper light fixture to replace the bare dangling bulb

Electrical: Details

The existing wiring supplying the office ran from the main panel in my apartment through conduit in the hallway to a hallway junction box just outside the office, then through the hallway-office wall into the office. By a great stroke of luck, a 3-wire cable of wire of sufficient gauge happened to run continuously from the main panel in my apartment to this hallway junction box outside the office. Only the hot and neutral wires were connected in my main panel, but it was a simple matter of hooking up the ground wire to the ground busbar in my main panel, and voilà!, there was the for the office.

By another stroke of luck, the connection between the hallway junction box and office was made with conduit (in old masonry buildings in Slovenia you'll sometimes find wires built directly into the brick wall), so replacing cable was a simple matter of pulling old wires out while running new cable in (no need to drill a chase through the hallway-office wall).

With a solid ground, neutral, and hot wire running between the office and my main panel; I could then begin electrical work in the office itself. This involved:

Replacing all existing wiring in the office with modern 1.5 mm2 VDE cable.
Replacing the, erm, makeshift wooden junction box hewn out of a scrap piece of construction lumber that held the main light/switch junction with a modern fire-retardant high-impact polystyrene junction box.
Installing a proper wall-mounted light fixture to replace the lightbulb dangling from the wall by its supply wires.
Cutting chases into the masonry wall for new conduit and junction/fixture boxes. This was unpleasant because of a constant worry of bothering the neighbors (cutting/drilling into masonry, whether with an angle grinder or rotary hammer drill, is loud).
Installing conduit and cable for outlets, and of course installing the outlets themselves.

Gallery: Electrical

The hewn-out scrap piece of construction lumber originally serving as the room's junction box.

Old wooden "junction box"...

The original supply wires for the room were routed through this hewn-out piece of scrap construction lumber. This was replaced with the modern molded plastic box at right. Note the very much welcome(!!) existing sub-surface conduit (the black tube continuing to the right)—this supplies the light switch and saved me from cutting a new chase in the masonry wall.

The fire-retardant high-impact polystyrene junction box replacing the original makeshift wooden box.

...and its modern replacement

The room's new main junction box, now made of more appropriate molded fire-retardant high-impact polystyrene. The main supply enters through the wall, then continues to the right through sub-surface conduit to the light switch and new outlets. The two masonry anchors will hold screws for a light fixture.

Original bare lightbulb...

The original bare lightbulb, seen dangling from the wall by its supply wires. If you look closely you'll see that electrical connectors are exposed about halfway along the exposed portion of the wires; you can also recognize the wooden junction box from the previous row of pictures.

...and its new replacement

The new wall-mounted light fixture replacing the original bare lightbulb. It is mounted over the new junction box shown above. Fun story: this is a repurposed light fixture from our old family home in Ljubljana, which we took with us after moving out but didn't find a place for in our new home.

The rectangular cavity hewn out of the masonry wall to hold a new electrical box.

Hewn-out cavity for a new electrical box

This hole will hold a new electrical box with the room's light switch and an outlet. I used an angle grinder and hammer drill to cut the hole in the masonry wall.

Checking new box is flush...

Here I am using a straight-edge to ensure the face of the new box is flush with the plane of the existing wall. The surrounding gaps are then filled with a gypsum-based plaster.

The new electrical box

The "rough-in" installation of the new electrical box—the box is installed with a gypsum-based plaster (gips in colloquial Slovene). This will hold a light switch and outlet.

A new chase cut into the masonry wall to hold conduit and cable for a second outlet.

Cutting a new chase

A new chase cut into the masonry wall with an angle grinder to hold conduit and cable for a second electrical box, which will hold an outlet supplying the computer desk.

Installing new conduit

New conduit to hold the cable supplying the computer desk outlet. You can see the outlet's box already installed flush with the wall on the right.

The installed new conduit, with the chase filled in with plaster.

Conduit installed!

The installed conduit, with the chase filled in with the same fast-setting gypsum-based plaster used to install the junction boxes. I painted this over provisionally with a lime-based whitewash, but would later repaint the whole room in a warmer color.

Refinishing timber framing

Re-exposed structural timbers after removing the original plaster coating.

Background: My building is masonry, but the roof is timber-framed. I happen to live on the top floor (i.e. under the timber-framed roof), and some of the structural timber framing supporting the roof happens to run through the office room. Unfortunately (at least if you ask me) this timber framing was covered with a plaster coating, concealing the beauty of the underlying wood! I am a sucker for timber framing, so I decided to expose and refinish the structural timbers. Here is the process:

Process

Roughly scraping the plaster off the timbers with a thick-bladed 5-in-1-style putty knife.
Grinding off lingering plaster bits with a flap disk attachment on an angle grinder.
Sanding down the timbers with a random orbital sander.
Refinishing the timbers with tung oil.

Aside: worrying about bothering the neighbors

Like cutting electrical chases into the masonry wall, sanding/griding the plaster coating off the timbers was unpleasant for all the noise it generated and the dust it raised. I don't mind the dust and noise myself—modern PPE protects you quite well—and was much more worried about bothering the neighbors! Angle grinders are loud, and the old interior door provides only token acoustic insulation, so the noise would ring out into the hallway and echo through the building. I did my best to work only in short bursts to avoid prolonged construction noise, and only at sane hours of the day. Thankfully no one complained.

Gallery: Stripping plaster off timbers

The first pieces of plaster coating removed from the timber framing.

Timbers covered in plaster

The timber framing was originally covered in a plaster coating, which I removed to expose the underlying wood. In this picture I've just started to remove plaster where the brace meets the post.

The timbers after scraping off the bulk of the coating.

First pass complete...

I first roughly scraped off the plaster coating with thick-bladed putty knife. I then made two more passes to remove the remaining plaster—first with an angle grinder with a flap disk attachment, then with a random-orbit sander.

Sanding complete!

This picture shows the timbers after grinding off the remaining plaster, then sanding with a random orbit sander. I would later fill the gaps between the timbers and walls with plaster before painting.

Angle grinder and PPE layed on the floor.

Tools

I did the bulk of the timber refinishing with an angle grinder and flap disk attachment, which did a good job of quickly removing large amounts of combined plaster-wood material. I experimented with the spray bottle to cut down on the plaster dust, but adding too much moisture would wet the underlying timbers and clog up the grinder disk with wet sawdust.

Dust, dust dust!

Grinding the lingering plaster off the wooden beams kicked up a lot of dust in a small enclosed space. Thankfully there was a small window for ventilation, but it still got pretty rough in there—the respirator proved invaluable. You can vaguely see a bit of the haze in the picture.

Oiling the timbers

I finished the timbers with a tung oil—I find the smell gentler than than linseed oil (the other standard candidate for a finishing oil), which is particularly relevant in a small space. I happened to have a can of tung oil lying around waiting to be used, and these timbers were a perfect opportunity to use it.

There was nothing much to this step, you wet a rag with oil and apply to the timbers. As hoped for, the color of the timbers deepened and the grain grew more visible. I'm pleased with the result!

Before...

The timbers after sanding off the original plaster coat but before oiling.

...and after

The timbers after finishing with tung oil. (I also painted the walls and patched the gap between the timber brace member and the wall in the meantime.)

Close-up

As hoped, the color of the timbers deepened and the grain of the wood grew more visible after oiling.

Painting

The room after the first coat of paint, with splotches and masking tape visible.

The room after the first coat of paint, with horizontal masking tape delineating the accent region.

Background: I painted the room with a limewash paint made by Kreidezeit GmbH, composed of marble lime hydrate, marble powder, sinter water, and methyl cellulose as a binding agent and thickener.

I chose a limewash paint for for its vapor diffusivity, natural composition (lack of VOCs, organic solvents, synthetic resins, etc. made sense in a small, enclosed space), good bond to the masonry substrate, and because the high alkalinity dramaticaly reduces the risk of mold.

The process was more or less standard:

Process

I first patched cracks and gaps in the walls and ceiling using gypsum-based plaster, and went over particularly rough areas with a spackle-like filler compound to create a smoother surface to accept paint.
I protected the timbers, window and door trim, and utilities with masking tape—I'm not skilled enough to trust myself to cut in by hand around all the nooks and crannies!
I applied an initial base coat of paint over the entire room.
I finished the bottom third of the room with a pastel-yellow accent, and the remainder of the walls and ceiling with a second coat of white.

Gallery: Painting

Plastering materials layed out on the floor: spackle knife, plaster, and bucket for mixing.

Plaster for patching gaps

I used fast-setting gypsum-based plaster (colloquially gips in Slovene) to patch gaps between the timbers and wall, and a finer spackle-like compound to patch fine cracks in the walls.

A visible gap running between a brace in the timber framing and the masonry wall.

Note the gap...

Note the gap running between the wall and the brace of the timber frame structure, which required patching before painting.

The gaps between timber members and wall patched with plaster.

...now patched with plaster

The gap is now patched and ready to be painted over. I smoothed over the various other cracks and flakes on the walls and ceilings with a combination of sanding and plaster.

Masking tape applied to timbers and window trim.

Protective masking tape on

I protected the timbers, window and door trim, and utilities with masking tape—a skilled painter might have cut these areas in freehand, but I'm not skilled!

Mixing pastel yellow pigment into paint with a paddle attachment and corded electric drill.

Mixing paint

The limewash paint I used did not come colored—you color it by mixing mineral-based pigment into a generic white "base" paint. I opted for a pastel yellow accent color, which I felt would cheer up the space.

A zoomed-out view of the office with the first coat of paint applied.

First coat complete

Here is the first coat, which I applied uniformly over walls and ceilings. It looks white, though is in fact slightly yellow-tinted.

A laser level being used to lay out a level line around the room for the yellow accent.

Laying out accent area

I used a laser level to lay out a level line around the room to define the region for the yellow accent—I chose the height at which the brace meets the post in the timber framing. A laser level is perhaps overkill for this small space, but why not use the toy if you're lucky enough to have it?

Rolling on the yellow paint for the accent region.

Rolling on paint

I painted most of the room with a roller (and used a brush where the roller could not reach). Here I am rolling on the yellow for the accent area.

The painted room with masking tape removed.

All done with painting!

Here is the painted room with paint dry and masking tape removed. The lower pastel-yellow accent region came out more subtle than I envisioned, partly because the warm-yellow light bulb illuminating the room tints the upper, nominally white, region yellow too, lowering the contrast with the yellow bottom. But I think the subtleness works—it's not too overbearing and brings out the color and grain of the wood timbers.