At what point - regarding R105.1 and R302.1 Accessory structures

[rktect 1]

We are re-evaluating a few things. Specifically at what point do you change requirements from the "standard way of doing it" in regards to sheds and detached garages.

Specifically sheds have now grown from 8x8 to 10, 12, 14 by 10, 12, 14 feet and greater these days. Our shed handout just says to give us some plans (well, within reason) but remember to use either a 4" slab or concrete piers. The building code this falls under appears in R105.2 Work exempt from permit #1 with floor areas less than 120 sq. ft.

So, at what point do you start plan review of a shed construction and it starts to resemble more a detached garage construction?

If 120 sq. ft., a 10x12 shed would probably need a full 4" concrete slab in order to get anchor bolts within 12" of each corner and 6 feet on center as well as a turned down footing? Full depth protection from frost (42" for our area). Ceiling joists at 16" o.c. to align with roof rafters.

Per R302.1, allowing a 120 sq. ft. shed to be located within 5 feet of a home will require rated walls and eaves????

Thoughts?

I am sure some will say this is overkill for 120 sq. ft. but the code is the code, yes? What about 130 sq. ft., 140 sq. ft, 160 sq. ft????

 

[mtlogcabin]

2012 IRC

Frost protection not required

R403.1.4.1 Frost protection.

Except where otherwise protected from frost, foundation walls, piers and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:

1. Extended below the frost line specified in Table R301.2.(1);

2. Constructing in accordance with Section R403.3;

3. Constructing in accordance with ASCE 32; or

4. Erected on solid rock.

Exceptions:

1. Protection of freestanding accessory structures with an area of 600 square feet (56 m2) or less, of light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.

2. Protection of freestanding accessory structures with an area of 400 square feet (37 m2) or less, of other than light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.

Rated walls not required

R302.1 Exterior walls.

Construction, projections, openings and penetrations of exterior walls of dwellings and accessory buildings shall comply with Table R302.1(1); or dwellings equipped throughout with an automatic sprinkler system installed in accordance with Section P2904 shall comply with Table R302.1(2).

Exceptions:

1. Walls, projections, openings or penetrations in walls perpendicular to the line used to determine the fire separation distance.

2. Walls of dwellings and accessory structures located on the same lot.

The 2009 IRC had 200 sg ft with no permit. We increased the IBC to match the IRC and did not go back under the 2012 editions.

 

[JBI]

mtlogcabin beat me to the punch (again!).

Also State or Local enabling legislation may provide for other thresholds as well.

NYS for example allows jurisdictions to exempt Residential accessory structures up to 144 s.f. from permit requirements and many, if not most, allow the exemption.

Our Statewide Factory Manufactured Building (Modular) program exempts accessory structures up to 400 s.f. from State review which makes it easier for the pre-fab shed folks to do business.

 

[steveray]

We are at 200sqft exempt and I couldn't be happier....

 

[@david]

In Virginia all AHJ's are exempted from requiring a permit up to 256 sq ft all use groups except F-1 and H

 

[Mr. Inspector]

Build your garage here in PA up to 1,000 sq ft and any hight (if no local change).

 

[steveray]

Build your garage here in PA up to 1,000 sq ft and any hight (if no local change).

That explains alot of what I have seen in PA....

 

[Francis Vineyard]

R104.11 Alternative materials, design and methods of construction and equipment.
The provisions of this code are not intended to prevent the installation of any material or to prohibit any design or method of construction not specifically prescribed by this code, provided that any such alternative has been approved. An alternative material, design or method of construction shall be approved where the building official finds that the proposed design is satisfactory and complies with the intent of the provisions of this code, and that the material, method or work offered is, for the purpose intended, at least the equivalent of that prescribed in this code. Compliance with the specific performance-based provisions of the International Codes in lieu of specific requirements of this code shall also be permitted as an alternate.

To my knowledge one of reasons Virginia increased the footprint to 256 sf. is most of these pre-fab structures that currently come across my desk have engineered specs availble from the manufacturer for wind anchorage with stakes and cables instead of concrete footings.
Virginia also amended R403.1 with an exception for the concrete footing.

R403.1 General. All exterior walls shall be supported on
continuous solid or fully grouted masonry or concrete footings,
wood foundations, or other approved structural systems
that shall be of sufficient design to accommodate all loads
according to Section R301 and to transmit the resulting loads
to the soil within the limitations as determined from the character
of the soil. Footings shall be supported on undisturbed
natural soils or engineered fill.
Exceptions:


1. One-story detached accessory structures used as tool
and storage sheds, playhouses and similar uses, not
exceeding 256 square feet (23.7824 m2) of building
area, provided all of the following conditions are
met:

1.1. The building eave height is 10 feet or less.

1.2. The maximum height from the finished floor
level to grade does not exceed 18 inches.

1.3. The supporting structural elements in direct
contact with the ground shall be placed level on
firm soil and when such elements are wood they
shall be approved pressure preservative treated
suitable for ground contact use.

1.4. The structure is anchored to withstand wind
loads as required by this code.

1.5. The structure shall be of light-frame construction
whose vertical and horizontal structural
elements are primarily formed by a system of
repetitive wood or light gauge steel framing
members, with walls and roof of light weight
material, not slate, tile, brick or masonry.