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Texas Building Codes

Building Code          

 

Roof Drainage Building Codes & Standards

 

International Code Council - International Residential Code 2006

 

Ch. 8 Roof-Ceiling Construction: Section R801

 

R801.3 Roof Drainage

 

“In areas where expansive or collapsible soils are known to exist, all dwellings shall have a controlled method of water disposal from roofs that will collect and discharge roof drainage to the ground surface at least 5 feet (1524 mm) from foundation walls or to an approved drainage system.”

 

International Residential Code 2000 Commentary - Vol. 1

 

“Saturated expansive or collapsible soils can lead to foundation failures because their additional loads are imposed on the foundation wall. To minimize the potential for the soil adjacent to the foundation wall to become saturated due to roof drainage, the code requires that the roof drain 5 feet (1524 mm) from the foundation.”

 

Ch. 4 Foundations: Section R401.3

 

R401.3 Drainage

 

“Surface drainage shall be diverted to a storm sewer conveyance or other approved point of collection so as to not create a hazard. Lots shall be graded to drain surface water away from foundation walls. The grade shall fall a minimum of 6 inches (152 mm) within the first 10 feet (3048 mm).”

 

Exception:Where lot lines, walls, slopes or other physical barriers prohibit 6 inches (152mm) of fall within 10 feet (3048 mm), the final grade shall slope away from the foundation at a minimum slope of 5 percent and the water shall be directed to drains or swales to ensure drainage away from the structure. Swales shall be sloped a minimum of 2 percent when located within 10 feet (3048 mm) of the building foundation. Impervious surfaces within 10 feet (3048 mm) of the building foundation shall be sloped a minimum of 2 percent away from the building.

 

International Residential Code Commentary - 2000

 

Along with the proper support for a structure through the foundation system, adequate preparation of the building site is necessary to keep water drainage away from the supporting foundations. Proper site drainage is an important element in preventing wet basements, damp crawl spaces, eroded banks, and possible failure of a foundation system.

 

One of the most important considerations is the arrangement of structures on a building site in a manner that retains natural drainage patterns and minimizes the alteration or disturbance to existing grades. If the designer keeps such factors in mind, the result will be a reduction of ground surface stabilization problems and opportunities for differential settlement through the reduction in the use of fills. A detailed treatment of drainage design is beyond the scope of this document; therefore, only rough guidelines can be provided for areas where a more comprehensive set of grading regulations does not exist.

 

As illustrated in Commentary Figures R401.3(1) and R 401.3(2) , drainage patterns should result in adequate slopes to approved drainage devices that are capable of carrying concentrated runoff. In some cases, control of concentrated roof runoff by gutters and downspouts may be needed, and if gutters and downspouts are used, provisions should be made to discharge runoff in order to prevent soil erosion. Refer also to Section R801.

 Diagram of approved downspout extension.

 

           

 

Texas Administrative Code

 

Title 22............Examining Boards

 

Part 23............Texas Real Estate Commission

 

Chapter 535....General Provisions

 

Subchapter R..Real Estate Inspectors

 

Rule 535.228: Standards of Practice: Inspection Guidelines for Structural Systems

 

(a) Foundations - the Inspector shall:

 

(8) report as in need of repair conditions or symptoms that ay indicated the possibility of water penetration that are present and visible, such as improper grading around foundation walls or plumbing leaks; and

 

(9) report as in need of repair conditions that are present and visible and may be adversely affecting foundation performance, such as erosion or water ponding.

 

(h) Roof, roof structure and attic. The inspector shall:

 

(11) report as in need of repair deficiencies in visible installed gutter and downspout systems.

 

International Code Council- International Residential Code 2006

 

Energy Star

 

Indoor Air Package Pilot Specification - April 4, 2005

 

1. Moisture Control Required Measures References Water Managed Roofs

 

1.1Provide Minimum No. 30 roof felt under layment or equivalent.

 

1.2 In IECC 2004 Climate Zones 5 and higher, provide self sealing water protection membrane ice flashing over the sheathing at the eave extending 2 feet inside the exterior wall plane.

 

1.3 Provide metal drip edge at all exposed roof decking.

 

1.4 Provide self-sealing bituminous membrane at all eaves, valleys and penetrations except in climates with less than 20 inches annual rainfall.

 

1.5 Provide Insulated wind baffle or other air barrier to block wind washing at all attic eave bays in roof assemblies with soffit vents.

 

1.6 Provide step flashing at all intersections of roof and walls with the exception of continuous flashing at metal and rubber membrane roofs. Metal “kick-out” flashing shall be provided at the end of roof/wall intersections to direct water away from wall. Drainage plane above shall be directed water flow onto and not behind flashing. Intersection wall siding shall terminate a minimum of 2 inches above roof. HUD/NAHB specs for gutters and downspouts

 

1.7 Direct roof water from house with either:

 

Guttering and downspouts shall empty to lateral piping that deposit(s) water on finish grade a minimum of 5 ft. from foundation, or in limited spaces, deposit to underground catchment system that carries water 10 ft. from foundation.

 

In dry climates with less that 20 inches annual rainfall as shown in EEBA Builder Guides, provide minimum 18” roof overhangs that deposit water to grade sloped away from home.

 

References

 

Copper Development Assn. Design Handbook, Sec. 4

 

Moisture Control Handbook

IRC

 

EBBA Builder Guide

Moisture Control Handbook

 

EEBA Builder Guide

EEBA Water management Guide

 

IRC code 801.c

EEBA Builder Guides

 

HUD/NAHB specs for gutters and downspouts

Moisture Control Handbook

IRC

   

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