My Cape-Office Build-Out

We moved into my 1952 Cape last December.  Winter was upon us, no time or desire to start any of the major renovation and energy updates I have planned.  My office was moved temporarily into the extra basement bedroom with a plan to build-out a new office adjacent to the bedroom.   This weeks blog is all about this project.

The future office space.

The southwest corner of the basement contains the extra bedroom (which has a code compliant Egress window) and a space to the southeast had a wall covering but no separation from the rest of the basement.  The bedroom space takes about 14 of the 24 feet available along the south wall, leaving approximately 10 feet for my office.  Plenty of space for my needs.

First step-Demo.  The existing wall covering of the future office space consisted of 1/4 inch inexpensive wood paneling in 4 x 8 sheets fastened to 2 x 2 wood furring strips in direct contact with the concrete block foundation wall (which is a code violation in the state of Minnesota.  A one inch space must be maintained between any wood framing and any concrete below grade wall).  The 2 x 2’s were not fastened directly to the concrete which made their removal easy.  There was also a suspended grid ceiling which needed to be removed.  The concrete floor was simply painted, no demo required for the floor.

Demo in progress.

A closet in the basement bedroom that divided the bedroom from the new office was also removed exposing a structural beam supporting the main floor.  A metal column supporting the beam was buried inside this wall.  I had attempted to level the main level floor before we moved in with only some success, this attempted had lifted the beam just enough so it was no longer being supported by the metal column.  A few twists on the adjustment screw remedied the problem.

Foundation insulation.  There was no insulation between the wall finish and the block foundation wall.  I knew I wanted to add some, but not so much that I stopped all heat from moving through the concrete block wall.  This home has always had some heat moving through the foundation preventing the soil close to the foundation from freezing.  Completely stopping this movement of heat could potentially cause issues with the foundation.  I chose to insulate with 1/2 inch of extruded polystyrene (XPS) insulation with an R-value of 3.

Office wall detail.

Before I added the insulation I attached a polyethylene slip sheet to the floor joists and allowed it to hang in direct contact with the block foundation wall.  This 6 mil poly went from floor to ceiling.  The purpose of the slip sheet is to prevent any moisture, either vapor or liquid, from entering the wood wall assembly.  I then placed the 1/2 inch XPS insulation against the polyethylene and nailed a 2 x 2 top plate into the floor joists to keep the XPS temporarily in place.  The 2 x 2’s used for supporting the wall finish were added after the floor system was in place.

While I was adding the wall insulation, I also addressed the rim joist area.  The existing insulation was fiberglass batts which was doing nothing to stop the substantial air leaks along this area.  I cut and cobbled rigid insulation to help with the air sealing and improve the insulation level of the rim joist area.

I cut a piece of 2-inch XPS foam slightly smaller than the space between each of the floor joists.  The foam was pushed tight to the rim joist and an bead of expanding spray foam was added to help seal the gaps between the XPS and wood framing and flooring.

Rim joist insulation.

Because there is no mud sill, (a mud sill is a treated board that is bolted to the top of the concrete foundation wall.  The floor joists and rim board are fastened to this treated board), there is an open cavity in the webbing of the concrete blocks.  This open cavity can be a source of moisture and air leakage.  I added a piece of 1/2 inch XPS insulation, which was a cut-off from the wall insulation, to cap the top of the concrete block foundation.  This insulation was caulked to both the wall insulation, rim joist insulation and to the rim joists themselves.

Floor system.  I knew I wanted to add comfort to both the office space and guest bedroom.  Insulating the wall insulation was going to be an improvement, not being in direct contact with the concrete floor would also help.  I also wanted to keep any floor covering dry should there be some light flooding event.  (A major flooding event would cause extensive damage in any finished basement.)  I chose to install a product called Dricore.

Dricore is a 2 foot by 2 foot oriented strand board (OSB) panel with a plastic backing that has stand-offs preventing the wood from coming in direct contact with the concrete floor and allow water and air to move freely under the OSB panel.  This product is easily cut using traditional hand or power tools and has a tongue and groove edge that keeps the panels aligned.

Backside of Dricore panel.

I installed the Dricore panels tight to the XPS wall insulation.  I screwed a 2 x 2 to the Dricore panels along the XPS to help keep the panels together and to act as the bottom plate for the wall framing.  The wall framing was then finished by adding 2 x 2’s 16 inch on center.  The rest of the framed walls were completed using 2 x 4’s to divide the bedroom to the office and the office to the rest of the basement.

XPS insulation, Dricore floor and 2 x 2 framing complete.

The electrical system.  During the demo of the existing space, I realized the electrical circuit feeding this area also fed an outside receptacle, the microwave in the kitchen along with one of the walls in a bedroom all the way up on the second floor.  In demoing the electrical, it was clear that who ever did the wiring in this space was not an electrician.

I separated the wiring that went upstairs (I will address this issue when those spaces are remodeled) with the basement office and bedroom space.  I ran a new 15 amp circuit dedicated to just these basement areas.  Bedrooms and offices are required to be arc-fault protected and because the circuit is in a basement, ground fault protection is also provided.  Both these functions are achieved using an arc-fault circuit interrupter (AFCI) / ground-fault circuit interrupter (GFCI) combination breaker.

Wall finish.  With the insulation, floor, framing and electrical work completed, I moved to the wall finish.  I chose drywall because it is easy to work with and can be painted a light color which will help lighten a dark basement.  I hung, taped and painted the drywall myself.  I don’t mind hanging and painting, but I dislike taping drywall.  If this were a project for a customer, I typically would not attempt the taping.  Seeing it’s for me, I can live with the small imperfections.  I maintained at least 3/4 of an inch gap between the basement floor and drywall.  A small amount of water temporarily in the basement shouldn’t be an issue.

Drywall hung, working on taping.

Floor covering, ceiling and trim.  I chose an 18 x 18 carpet square in a dark grey as my floor covering.  The door, door casing and floor base are all stained black.  The walls were all painted a light grey, almost a light blue.

Because my office is located directly below the kitchen, and I know that the kitchen space will be receiving a remodel in the future, I chose to install a dropped grid ceiling.  The acoustical tiles provide some sound deadening, are easily replaced if there should ever be any water damage and still provide access to the electrical, heating and plumbing above.

Painted and carpet installed.

I still have a few small projects to complete in the office and the entire guest bedroom to build out, hopefully will have those projects completed by late spring.  Summer will bring much bigger projects.

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