Arch. Myriam B. Mahiques Curriculum Vitae

Wednesday, November 14, 2018

What is a ¨Garage conversion¨ into ADU Accessory Dwelling Unit_

A common problem: the side wall and the eave are very close to the property line. A modification of the eave to be 1 hr fire rate is needed and the 1 hr fire rate assembly for the wall must be proven. Picture from my personal archives. It has been cropped to protect the homeowners' privacy.

"Garage conversion" into ADU or Accessory Dwelling Unit means the conversion of an existing garage into a habitable dwelling. This is permitted in California due to the Bill Senate 1069. For the City of Los Angeles, the link below will help for a better clarification:

Basically, it is established that, given the housing crisis, their high costs (estimated in 2.5% on top of the national average), plus the expensive rents (50% on top of the national average), barriers against the construction of ADU would be eliminated within certain restrictions. Among those restrictions would be maximum percentages of square footage compared to the main unit, maximum square footage allowed, set backs, off street parkings, etc.
This post is referred to general outlines and each property would be restricted by the Zoning code corresponding to its City.

The main question is, can a garage be converted into a dwelling? Yes, even if it is detached or attached to the main house.
There are two important issues:

1. If the garage is not modified and its original square footage (per records) is kept, the set backs (front, rear, side distances to the property lines) stay "as is" no extra off street parking is needed.
2. If the homeowner decides to enlarge the garage, then all restrictions of set backs and off street parkings apply as if it were a brand new second unit. With this being said, there must be verified if the parking spaces and back up clearances fit into the lot.

There are particular cases, like in Carson, where the ADU could be considered a living space for a bachelor, with a basic kitchen, the bathroom could be new inside the ADU or the existing bathrooms inside the main house may be used (in an attached ADU).

One of the main problems I've seen, is that the homeowners consider the garage conversion is just only one floor plan, showing the garage as a dwelling. This is extremely incorrect, for a new conversion or for a legalization of a change of use that was made without a permit. The legalization means to submit plans of new construction for the works that do not have a record, so no permits have been paid for them and they were not subject to inspections.

To pass from an accessory structure like an inhabitable garage to a livable dwelling is object of many considerations. Mostly when the structure is from old times. Obviously, the codes employed E.G. 30 years ago, are not the same than the current ones, which have more safety measurements against fire and earthquakes.
The garage must comply then with construction requisites that must be approved under the current Codes. People who is meant to live inside an ADU has to be safe!.

So, basic plans and calculations needed for the (construction of a) garage conversion into an ADU are the following:

1. Architectural plans: site plan, floor plan, cross sections, electrical and plumbing layout, green code forms, elevations (facades), construction details (walls assemblies, ventilations, LID low impact development, fire rated details, etc), construction notes, roofing, etc.
2. Structural plans and calculations: a garage must not have a ceiling. If originally it had collar ties, then they wont be enough to support the new drywall ceiling. Ceiling joists would be added, and it means new loads to the existing structure. There must be a new foundation below the former garage door, with epoxy connection to the existing foundation. Foundations must be revised. The existing slab concrete must be leveled and a vapor barrier provided. New shearwalls upgrades (walls against earthquakes) should be added.
Depending on the City, the structural plan check could be more or less intensive.
3. Energy calculations and plans: This is Title 24 which applies to heating (and this is an obligation), windows coefficients and hot water.
Some landscape design may be requested as well, like new trees planting, and or planters.

Ceiling insulation inside a garage illegally converted. We should call it out R30 insulation. Ceiling joists were added. Structural calculations will be needed. The picture is from my personal archives. It was cropped to protect the privacy.

The approval process at the City is similar to any new construction, though all departments needed for a new house must be passed (approved). This includes Sanitation as well. As always, construction works must not be commenced until the plans are approved and the permits are paid. They include only one time payment for the School District.
If the conversion is illegal (without a permit), we recommend to ask for an extension to allow time to prepare the plans. Once the permits are paid, inspectors would be called to inspect the works in stages. Some areas must be open to allow access and technical evaluation.

If you have any question, we are here to help you. A consultation to the Planning department of your City would be the first step.

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