Bruce and all,
As an owner and resident, I strongly support the board efforts to maintain high standards of responsible and timely decision making. I am grateful for the many examples of effective collaborations between the board and Hofeller Co. around so many difficult challenges lately, some requiring consultations with outside professionals and contractors. I remain confident that the new garage door can be another such example, despite the communication and technical problems we have experienced.
The purpose of the report attached below is to take a significant step towards more completely identifying, understanding and resolving the technical issues still plaguing this project. I have tried to ask the key questions and identify the kind of information needed by the board to predict and prevent forseeable problems. My investment of time and effort to produce the attached report was motivated by the persistent lack of this information.
In submitting this report, I hope to empower others to make use of it thereby reducing the burden of trying to convey it verbally in the heat of decision making. I would prefer to step back from the decision making process except to answer technical questions and thereby help preserve my capacity to serve as an effective consultant on technical matters.
Thank you,
Bob Cowherd
-------------------------
Garage Door Proposal: Four Questions
1. Ventilation: The concern raised was that the proposed garage door is solid and would reduce our ventilation area. The current open area of the garage was intended to meet the minimum code requirement for natural ventilation without the expense and nuisance of a mechanical forced air system.
Research: In order to reduce the probability of noxious gasses accumulating and infiltrating into adjacent dwellings, the code requires that “...the exterior side of the structure shall have uniformly distributed openings on two or more sides. The area of such openings in exterior walls... must be at least 20% of the total perimeter wall area. The length of the openings ...shall constitute a minimum of 40% of the perimeter” (Massachussetts Building Code 780 CMR Section 406.3.3.1 on Parking Garage Openings).
Analysis: Our current garage opening extends along 46% of the perimeter. Our current total perimeter wall area is 4427 square feet. The required 20% opening would be 885 square feet. Our current 717 square feet of openings is only 16%. The proposed change would reduce the total opening area to 627 square feet, 14% of the code required opening area. It would be reasonable for this non-compliant condition to be cause for health, safety, and legal concerns to residents, Cambridge Inspectional Services, and insurance carriers.
Recommendation: Investigate an open grating door option. Code inspectors may well tolerate our current situation in the spirit of a grandfather clause. However, inspectors visiting the site are likely to be highly sensitive to new work that “extends a non-complying condition” such as is being proposed.
2. Garage Height Clearance: There is concern that the reported new door clearance of 6 feet 10 inches might impose a new limitation on the height of vehicles and roof racks able to safely use the garage.
Research: In order to ensure that future users of the structure will be granted reasonable access to the use of the garage, the state code calls for a minimum garage ceiling height clearance of 7 feet (Massachusetts Building Code 780 CMR Section 406.2.2 Parking Garage Clear Height). Our construction drawings refer to a City of Cambridge statute requiring a free clearance of 7 feet 6 inches throughout the garage (Cambridge Cohousing Construction Drawings Sheet S-3 Section C). These construction drawings show a 3-1/2 inch vertical space below the garage ceiling to locate light fixtures and sprinkler system above this 7 foot 6 inch minimum height clearance. Our sprinkler system currently stands at 7 feet 6-1/2 inches clear height. Consistent with this requirement, the current garage door was designed to provide a height clearance of 7 feet 6 inches, or an effective door clearance of 7 feet 3 inches given the geometry of the driveway slope and vehicle wheelbases.
History: The structural framework of the garage permts the potential of a 7 foot 6 inch clearance throughout. However, missteps during the construction of the project resulted in the installation of HVAC and waste pipes significantly below the 3-1/2 inch allotment. The waste pipe insulation and plaza deck drain line installation in recent years has further reduced the garage height clearance down to 7 feet 1 inch. Even though the garage door can open to a height of 7 feet 6 inches, the electric motor is unnecessarily set to stop at a height of only 6 feet 11 inches, an effective door clearance of 6 feet 8 inches. The low clearance has prevented service vehicles from entering to tow or jumpstart stranded vehicles.
Analysis: The further reduction of the door clearance to only 6 feet 10 inches will yield an effective height limitation of 6 feet 7 inches. The primary rationale for the new garage door is to reduce the frequent repair bills when drivers inadvertantly damage the door rails coming through a doorway that is too narrow. It would be unfortunate to miss the opportunity to also redress the threat of similarly expensive repairs when an overloaded roof racks hits and damages the open door overhead. It is preferable for the limiting height in the garage be imposed by the soft and easily repaired/replaced pipe insulation currently set at 7 feet 1 inch.
Recommendation: Choose a different garage door mechanism, or design a modification for the current preferred option, in order to maintain a 7 foot 4 height clearance (effectively allowing a vehicle/rack height of 7 feet 2 inches).
3. Noise and Vibration: During design and construction there was a significant effort made to ensure that the residents of unit 104 would not be unduly burdened by disturbances from the operation of the garage doors. The decision to locate the motor outside the garage mounted on a massive and stiff structural girder supporting three floors and a roof was in part informed by these concerns.
Recommendation: Order the “low vibration” optional motor and mount it with vibration damping connections to a rigid structural steel bracket mounted to the major steel beam adjacent to the center line of the proposed garage door opening.
4. Design of Doors and Openings: There is a concern that the contractor will install a fixed grating and new doors in a manner acceptable to residents.
Recommendation: Provide drawings, product cut sheets, and specifications reflecting the anticipated appearance and performance of the finished installation.