Last winter I purchased a small Cape style home which I plan on renovating over the next several years. My original plan was to tackle the upper level this summer, where there are two bedrooms and a bath. Plans changed this spring after a closer inspection of the exterior.
My last posting about the home was the start of the exterior work, which included removal of two concrete steps, replacing a section of rim joist and a discussion of why I chose to use Henry Blueskin VP100 as a WRB. Read that posting here.
The past couple weekends has found me working on the small (3′ x 12′) addition. The reason for the addition is the main floor bedroom is only a little over 8 feet wide and the only place for a queen sized bed to fit in the room is close to the door. The door hits the bed and won’t allow it to open a full 90°. Three more feet would make a huge difference.
The first step was to remove all the siding from the north side of the home. I knew there would be a suprise waiting for me under that painting of the sun.
The old window and door where covered with polyethylene sheeting on the outside. Luckily there was very little rot. The bigger problem was the electrical wiring, several junction boxes were buried in the wall.
One additional surprise I had was a cold air return on the exterior wall leading to the upper level of the home. This entire stud bay was uninsulated and was using the building cavity as the ductwork. Every time the furnace ran, any air leakage points in this “duct”, which there where many, would pull outside air through the building cavity and bring it to the furnace. Not good when outdoor temperatures are -20°.
The foundation for the addition included the digging of three holes. I chose to place the addition on piers rather than making any changes to the existing foundation. I live in climate zone 7 which required the footings to be dug five feet deep.
I then poured a 12 inch bell footing and placed an 8 inch round concrete form on top of the 12 inch footing. The concrete was hand mixed and placed into the form. A 1/2 inch concrete anchor was placed in the concrete to hold the addition to the footing. The footings where then allowed to cure for a few days.
After the concrete cured, I attached a short piece of treated 6 x 6 to the footing using a metal hold-down bracket. The 6 x 6 was notched to allow a pair of 2 x 8’s to be attached to the 6 x 6.
The floor joists consist of 2 x 10’s attached to the home’s rim joist using metal brackets and structural screws. The entire assembly needed to be insulated and that insulation needs to stay in place. I added OSB to the bottom side of the assembly to both retain the insulation and act as my main air barrier. The one seam and all the edges were taped with Zip Systems tape.
After the floor framing was completed, the next step was to add insulation for the floor. Typically you can get about R-30 worth the fiberglass batt insulation out of a 2 x 10 space. I chose to go with a double layer of R-21 fiberglass batt. The insulation ended up slightly compressed, which will lower the rated R-value, but I will still end up with a much better insulation performance had I installed just the R-30 batt.
With the insulation installed I next needed to add a vapor control layer. Minnesota code requires a class I or II vapor control layer on the warm in winter side of all walls, ceiling and floors. I have a roll of CertainTeed’s MemBrain smart vapor retarder which I decided to try out. This product falls under the class II vapor control layer. Read more about MemBrain and other types of vapor retarders here.
Now that the floor system is insulated and decked, I could concentrate on wall and roof framing. I needed to install in a 12 foot header into the side of the home to support the opening into the addition. The engineering for the header called for a double 10 inch LVL header. I increased the header size slightly to a double 12 inch LVL. Had to have the entire family help lift the double LVL into place. (Myself, a pair of teenage girls, a girl in her mid 20’s, and my significant other.) Unfortunately, I didn’t get any pics of the wall after the header was installed.
Next came the addition wall and roof framing. The walls are typical, 2 x 6, 16 inch on center framing with OSB sheeting. The roof is hand framed 2 x 10, 24″ on center and OSB sheeting.
There is an existing sliding patio door in the bedroom that will eventually be removed. This patio door is currently the only means of egress. I added two windows to the room in the new addition. Both are sized for egress.
The windows I chose are fiberglass manufactured about an hour away. I didn’t want to spend a lot of money on a high end window, but did want to upgrade the performance from what is currently in the home, a mix of 1952 original windows and a few newer units from the 1980’s. I upgraded the window performance from the climate zone 7 code minimum U-.30 to U-.26. In comparison, a great window might have a U-.15 rating. Read more about the window rating stickers here.
Next up, roofing and cladding. Stay tuned.