Studio Z - Project Portfolio - Building an office, addition

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Under Construction: Building an addition and a home office/garage

Project Diary
A Homeowner's Notebook
(click on small images to see larger versions)

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Previous summer and fall: Homeowners work with Studio Z and the contractor to take the project from an initial concept to a fully elaborated design. Studio Z completes the final "construction documents" (blueprints and specifications) in the fall, and the plans are submitted to the city authorities for approval. Demolition of the existing deck and old garage takes place in December. Scheduling begins for the masonry subcontractor, who will dig and pour foundation footings.

February 5: The masons begin excavating for the foundation footings. They immediately discover a problem: an old cistern, used to collect rainwater long ago, is located precisely where the foundation for the new addition meets the house. See Expect the Unexpected (at left) for more details. Digging trenches for the garage footings proves uneventful.

February 13: Footings for the garage/office foundation are poured, using two full trucks worth of concrete.

February 17: The concrete block foundation for the garage office has been finished.

February 20: The old cistern has been emptied out, inspected, and filled up to the level of the footings with pea gravel. The footings for the addition are then poured.

March 5: The concrete block foundation for the mudroom addition has been laid down, and the old concrete back door steps have been removed.

March 8: With the foundation walls done, the carpenters can begin work. The floor deck of the addition has been framed, and the walls are going up.

March 14: The walls are up and sheathed with plywood, and the roof of the addition is being framed.

March 20: The addition roof has been framed, and the interior partition wall, with pocket door hardware, has also been framed.

March 27: Casement windows have been set in the rough openings on the addition, and the crew has begun to shingle the roof. The small roof over the back door, and the brackets which support it, has also been framed and joined to the main roof.

March 30: The roof shingling has been finished, and the new back door has been hung in its opening. Since the addition is now weather-tight, interior work can begin.

April 3: Work resumes on the garage/office, anticipating the arrival of the structural insulated panels. The old concrete slab is removed (with some difficulty), and 4 inches of sand is compacted to form the base for the new slab; the sand is covered with a vapor barrier and wire mesh.

April 6: Plumbing and heating pipes for the addition have been roughed in and are awaiting plumbing and mechanical inspections.

April 10: The slab for the new garage was poured after the prepared base was inspected by the city authorities.

April 12: The first batch of SIPs (structural insulated panels), including the downstairs and upstairs walls, arrive on site and are unloaded.

April 13: Siding has started to go up on the addition; rather than wood or vinyl, SZA and the contractor suggested a cementitious product which is less expensive and should be more durable.


April 17: With some extra help, the crew raised the wall panels for the first floor of the garage/office, each of which were fabricated in one piece. This process would normally be accomplished with a crane, but the site is not large enough.

April 18: The office roof trusses were delivered (at 7am) and left in the front yard until they could be carried back to the site - by hand.


April 23-26: The second story floor and wall panels are erected.

Room to Grow

The family that owns this small home in Ann Arbor was growing, and they really needed to move their home office out of their third bedroom so that their new daughter would have a room of her own. To accomplish this, they decided to demolish a tiny, one-car garage at the back of their property and replace it with a one-and-a-half car garage with a home office above it. The new building will be constructed with structural insulated panels (SIPs), rigid panels made of foam sandwiched between wood skins, making it very energy efficient.

The owners were very concerned that the home office/garage building would be too tall, and would overwhelm the property. Studio Z Architecture proposed that the roof be lowered, so that the building would appear smaller, while vaulting the ceiling to make the interior as spacious as possible. In addition, the complex roof shape will make the building appear smaller. They also considered making the siding wider on the lower part of the building and narrower above to make the building visually shorter.

The home office will be reached by a separate door covered by a small roof, and an interior stairway. The office will have many windows and two skylights.

Since the home had only one bathroom, the owners also decided to add a small mud room and half bathroom to the back of the house. An existing deck had to be demolished to make room for the addition, but it will be replaced with a spacious patio that blends into the back yard and garden.

Contractor: Washtenaw Woodwrights, Ann Arbor
Structural Engineer: Structural Design Incorporated, Ann Arbor
Project photography & diary text: Steven Norton

Expect the Unexpected
(click on small images to see larger versions)

It's always something. Everyone sensed trouble ahead when a half-circle of brick was discovered embedded at ground level in the existing house foundation after the deck was demolished. In fact, when digging began, the masons discovered an old cistern right where the foundation for the new addition would meet the existing house.

The foundation for the back part of the house (an old addition) was built right over the cistern, now filled with organic matter and old trash. The cistern was about 8 feet in diameter and 9 feet deep. Cisterns like this one are common in older Ann Arbor neighborhoods, and were used to collect soft rainwater for washing. But finding the foundation wall of the 1940's addition built straight across the cistern surprised even the oldest hands.

Moreover, the crew discovered that the foundation footings for that old addition - currently the back part of the house - are only 12 inches deep, 30 inches less than is required today. [The photo shows steel rebar poking into the dirt underneath the 12" footings of the old foundation.]

The organic matter in the cistern could not reliably hold the weight of the old and new foundations, so Studio Z assisted the contractor and homeowners in considering various options to bridge the cistern, including a grade beam and helical piers, or filling the cistern. Since the masons had found the cistern to be quite strong, it was agreed that the trash and dirt should be removed from the cistern, which was then filled with pea gravel up to the level of the new foundation footings. The top of the cistern was filled with concrete when the new footings were poured, resulting in a sound structure.

Studio Z also assisted the homeowners and contractor in finding an acceptable solution for the shallow footings on the old addition. A combination of rigid insulation laid in the ground along the outside of the old footings and more installed along the inside of the foundation walls would keep the ground under the old footings from freezing and heaving.

The old house held one final surprise: carpenter ants. When the human carpenters went to remove the unsightly remains of a first-floor roof on the old house addition, they uncovered a substantial nest of carpenter ants. The ants were dispatched with boric acid dust blown into the space between the floors, and damaged lumber was replaced. The structural damage done by the ants was limited - less, in the eyes of the contractor, than the mistakes made by whoever had built the second floor on the old addition.

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