Revised 11/29/06 Knox County Residential Building Codes Significant Changes From The 1995 CABO One And Two Family Dwelling Code To The 2006 International Residential Code All one and two family dwellings and townhouses built in Knox County after the new code adoption in early 2007 will be required to meet the requirements of the 2006 International Residential Code which can be ordered online at www.iccsafe.org or by calling the ICC store at 1-800-786-4452. The following is a list of significant changes from the previous code requirements of the 1995 CABO One and Two Family Dwelling Code and includes related administrative changes in the permitting and inspection processes. This is not an all inclusive list of all of the changes in the new code. Administrative Changes Other codes and ordinances Knox County will also adopt the other International Codes which will have some application to residential construction. The 2006 International Existing Building Code applies to the repair, alteration, change of occupancy, addition and relocation of existing buildings and the 2006 International Property Maintenance Code applies to all existing residential structures and premises. The 2006 International Codes for commercial construction will also be adopted and used for reference including the building, mechanical, plumbing, fuel gas, fire and energy codes. All existing Knox County Ordinances will continue to be enforced including the Zoning Ordinance for Knox County and the Minimum Subdivision Regulations for Knoxville and Knox County including storm drainage and erosion control regulations. Pre-approved plans All new permits will require 2 sets of plans to be submitted and reviewed under the new code before preapproved permits will be issued. No pre-approved permits will be issued based on plans reviewed under the old codes. Residential Building Code Changes Townhouse/Condo/Apartment - Page 1 - Section R101.2 Scope This code applies to the construction of multiple single-family dwellings (townhouses) not more than three stories in height with a separate means of egress and townhouse is defined as A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from foundation to roof and with open space on at least two sides. This now includes buildings that were previously considered to be condominiums. The International Codes do not recognize condominiums as a type of residential occupancy. Instead they classify the building as apartments which are regulated by the International Building Code and require a one-hour rated wall or as townhouses which are regulated by the International Residential Code and require a two-hour rated wall if they meet the definition above. Bottom line: Condominiums which are actually townhouses as defined in the code and are not apartments will now be required to have two one-hour fire rated walls or one two-hour fire rated wall with no plumbing or mechanical equipment, ducts or vents contained therein. Parapets extending above the roof line or fire rated roof sheathing or gypsum wrapbacks under the roof sheathing will also be required. Plan review and inspections by the Fire Prevention Bureau will not be required for townhouses. 1
Three stories above grade plus below grade basement - Page 1 - Section R101.2 Habitable space is permitted on four stories because basements will not count as a story if the first floor is: 1. Less than 6 ft. above the grade plane (avg. grade), 2. Less than 6 ft. above finished ground for more than 50% of the perimeter and 3. Less than 12 ft above finished ground at all points. CABO did not allow habitable space in a basement and 3 stories above grade. The Zoning Ordinance will still limit buildings to 3 stories with habitable basements or attics counting as a story. No permit required - Page 3 - Section R105.2 This section requires no permit for one story detached accessory structures less than 120 square feet in area but the building must still meet all zoning code requirements. CABO exempted no buildings. Retaining walls Page 3 Section R105.2 This section requires permits for retaining walls four feet or more in height or for any height retaining wall supporting a surcharge such as sloping backfill or buildings or other loads above. The CABO code did not specify when permits were required for retaining walls. Accessory structures - Page 9 - Section 202 Definitions This section limits accessory structures to 3000 square feet and 2 stories maximum. If larger they must be built by the International Building Code which has similar limits for Type V B (wood) U utility occupancy and requires larger accessory buildings to be classified as S storage occupancy and to be built of less combustible materials. There were no area limits under the CABO code. Rated exterior walls - Page 47 - Table R302.1 Exterior walls less than 5 feet to property line or fire separation distance must be one-hour fire rated. The distance was 3 feet in CABO. (note: 25% openings allowed from 3 to 5 & unlimited 5 & over) Garage separation - Page 52 - Section R309.2 This section requires 5/8 type x gypsum board on the garage ceiling if there is habitable space above. CABO required ½ gypsum board. Many builders use 5/8 type x already. Basement emergency egress - Page 52 - Section R310.1 Emergency egress directly to the outside is now required in a basement. This was not in CABO. Emergency egress opening size - Page 53 - Section R310.1.1 5.7 square feet is required for the second floor. Amended CABO allowed 5.5 square feet. The maximum sill height remains unchanged at 44. Emergency egress opening height - Page 53 - Section R310.1.2 A minimum net clear opening height of 24 is required. CABO was 22. Landings - Page 53 - Section R311.4.3 Exterior landings can only be 7 ¾ below the threshold. CABO allowed 8 ¼. Stair risers - Page 54 - Section R311.5.3 Amended section requires risers to be 8 maximum. Amended CABO was 8 ¼. The minimum tread depth will remain unchanged at 9 by amendment. Handrail height - Page 54 - Section R311.5.6.1 This section requires handrails to be a minimum of 34 in height. Amended CABO allowed 30. 2
Guardrails - Page 55 - Section R312.2 This section requires that guardrails shall not allow the passage of a 4 sphere (4 3/8 for open side of stairs). Amended CABO allowed 6. Townhouse 2 hour walls - Page 58 - Section R317.2 This section does not allow any plumbing, mechanical equipment, ducts or vents in a 2 hour wall separating townhouse units. Amended CABO did allow this. Foundation sill plate anchor bolts - Page 72 - Section R403.1.6 ½ diameter anchor bolts embedded 7 minimum spaced 6 ft. on center maximum or approved equivalent anchorage devices are required. Amended CABO allowed nails at 16 on center. Foundation wall bracing - Page 79 - Section R404.1.3 This section has been amended to allow foundation walls to be braced at the top as follows when the floor structure is parallel to the backfilled wall. If backfill is less than 4 feet, blocking is required at 4 feet on center in the first two joist spaces. If backfill is 4 feet or more, blocking is required 2 feet on center in the first three joist spaces. Foundation wall reinforcing condensed table - Pages 81, 82 & 84 - Tables R404.1.1(1), (2) & (3) The reinforcing requirements based on wall heights, backfill heights and type of fill have changed. This is a simplified chart for walls up to 10 feet tall with 60 PSF per foot below grade lateral soil load. Reinforcing Required for Wall Heights Block Size Block Type Backfill Height 7-0 7-4 8-0 8-8 9-4 10-0 8 Hollow Under 4-0 x None None None x x 8 Solid Under 5-0 None x x x x x 8 Hollow 4-0 x #4@48 #4@48 #4@48 #4@48 #4@48 8 Hollow 5-0 x #4@48 #4@48 #5@48 #5@48 #5@48 8 Hollow 6-0 x #5@48 #5@48 #6@48 #6@48 #6@48 8 Hollow 7-0 x x #6@40 #6@40 #6@40 #6@32 8 Hollow 7-4 x #6@40 x x x x 8 Hollow 8-0 x x #6@32 x #6@24 #6@24 8 Hollow 8-8. x x x #6@24 x x 8 Hollow 9-0 x x x x x #6@16 8 Hollow 9-4 x x x x #6@16 x 8 Hollow 10-0 x x x x x #6@16 12 Hollow 5-0 x x None None x x 12 Solid 6-0 x x None None x x 12 Hollow 4-0 x #4@72 #4@72 #4@72 #4@72 #4@72 12 Hollow 5-0 x #4@72 #4@72 #4@72 #4@72 #4@72 12 Hollow 6-0 x #5@72 #5@72 #5@72 #5@72 #5@72 12 Hollow 7-0 x x #6@72 #6@72 #6@72 #6@72 12 Hollow 7-4 x #6@72 x x x x 12 Hollow 8-0 x x #6@64 #6@56 #6@48 12 Hollow 8-8 x x x #6@48 x x 12 Hollow 9-0 x x x x x #6@40 12 Hollow 9-4 x x x x #6@40 x 12 Hollow 10 0 x x x x x #6@32 x indicates fill higher than wall which is not allowed or no value given in code tables. Values given for total fill such as 10 foot fill on a 10 foot wall are not valid because the code requires the wall to extend 4 above grade for brick and 6 above grade otherwise. 3
Foundation wall reinforcing alternate table - Pages 81, 82 & 84 - Tables R404.1.1(1), (2) & (3) The reinforcing requirements based on wall heights, backfill heights and type of fill have changed. This is a simplified chart for walls up to 10 feet tall with 60 PSF per foot below grade lateral soil load. Minimum 8 Block Maximum Heights 12 Block Maximum Heights Reinforcing Fill Ht. Wall Ht. Fill Ht. Wall Ht. Fill Ht. Wall Ht. Fill Ht. Wall Ht. None Hollow 4-0 8-8 5-0 8-8 None Solid 5-0 7-0 6-0 8-8 #4 @ 48 4-0 10-0 5-0 8-0 #4 @ 72 5-0 10-0 #5 @ 48 5-0 10-0 6-0 8-0 #5 @ 72 6-0 10-0 #6 @ 16 10-0 * 10-0 #6 @ 24 8-0 10-0 8-8 * 8-8 #6 @ 32 7-0 10-0 8-0 * 8-0 #6 @ 40 7-0 9-4 9-0 10-0 9-4 * 9-4 #6 @ 48 6-0 10-0 8-8 * 8-8 #6 @ 56 8-0 9-4 #6 @ 64 8-0 * 8-0 #6 @ 72 7-0 10-0 Blank fields indicate no values given in code tables. * Values given for total fill such as 10 foot fill on a 10 foot wall are not valid because the code requires the wall to extend 4 above grade for brick and 6 above grade otherwise. Backfill for solid block or solid filled - Page 81 - Table R404.1.1(1) 8 solid block was allowed 7-0 maximum fill and is now 5-0 with a maximum wall height of 7-0. 12 solid block was allowed 8-0 maximum fill and is now 6-0 with a maximum wall height of 8-8. Unvented crawl spaces - Page 94 - Section R408.3 The new code has very specific and detailed requirements for insulation, moisture control and conditioned air supply for unvented crawl spaces. CABO had no provisions for this. Cantilevered floor joists - Page 97 - Section R502.3.3 Cantilevers were limited to 24 in CABO. New tables provide regulations allowing up to 48 with 3:1 backspan ratio for light-frame bearing wall & roof and up to 72 for balconies with no roof. Header Spans - Page 102 - Table R502.5(1) New expanded tables are similar to 1992 CABO. Spans allowed have been reduced. For example in a wall supporting only the roof above a double 2 x 10 can only span 8-5 max. in a 20 wide house where CABO allowed a span of 10-0. Now a double 2 x 12 supporting the roof only in a 20 wide house can only span 9-9 where CABO allowed 12-0 Alternate wall bracing adjacent to doors or windows - Page 138 - Section R602.10.6.2 This section provides requirements for minimum sheathing width of 16 for 1 story & 24 for 2 stories on each side of a garage door. It requires 3/8 wood sheathing nailed 3 oc with 8d nails. Sheathing must extend over the header or tie downs must be used. Also requires at least one 5/8 anchor and stud tie down devices fastened to the foundation. CABO had nothing specifically for the bracing of narrow walls adjacent to openings such as garage doors. 4
Exterior wall covering water-resistive barrier required - Page 233 - Section R703.2 This section now requires felt paper or housewrap to be applied over studs or sheathing behind siding of all kinds. CABO did not require this. Masonry veneer requires extra wall bracing - Page 238 - Section R703.7 This code requires the wall bracing to be increased 1.5 times the minimum on the first story of a two story and on the first two stories of a three story building. CABO did not require this. Masonry veneer over wood roof - Page 238 - Section R703.7.2.1 This code requires a 4 x 6 x 5/16 steel angle with long leg vertical fastened to each stud with two 7/16 x 4 lag screws and a tripled roof structural member. The first rafter must have three 5/8 x 5 lag screws into each stud and the adjacent rafters must be nailed to it with two 10d nails every 16 oc. For slopes over 7:12 up to 12:12 the code requires 3 x 3 x 1/4 steel stops welded to the angle every 24. The code limits the height of the veneer over the roof to 12-8. CABO had no provisions for this. Triple rafters with a steel angle has been accepted but no specific design information was available. Masonry veneer wall ties - Page 241 - Section R7.3.7.4.1 Brick or stone veneer wall ties are required for each 2.67 square feet of wall area. CABO allowed 3.25 square feet per tie. For 24 horizontal spacing the maximum vertical spacing will be 16. For 16 horizontal spacing the maximum vertical spacing will be 24. Rafter ties and collar ties both required - Page 244 - Section R802.3.1 This section requires a ridge beam or girder if there are no ceiling joists or rafter ties parallel to the rafters at the level of the top plate or in the lower one-third of the attic height. Ceiling joists or rafter ties in the lower one-third of the attic height are required for every rafter. Collar ties in the upper one-third of the attic height or ridge straps to resist wind uplift are also required at no more than 4 feet on center. The previous code required rafter ties as close to the top plate as practical and did not require collar ties. Rafter spans - Page 244 - Section R802.5 This section reduces allowable rafter spans by the ratio of the height of rafter ties above the top plate divided by the height of the ridge. CABO had nothing. For example 2 x 10 rafters at 16 on center with no ceiling attached are allowed to span 23-2 with rafter ties/ceiling joists at the top plate but the maximum span is reduced to 15-6 if the rafter ties are raised up to the maximum one-third of the height of the attic. Rafter tie connection fasteners - Page 266 - Table R802.5.1(9) The new code requires more 16d common nails to fasten the rafter ties to the rafters as they are raised higher above the top plate. Unvented conditioned attics - Page 286 - Section R806.4 The new code has very specific and detailed insulation, moisture control and air supply requirements for conditioned attics. CABO had no provisions for unvented attics. Reroofing - Page 299 - Section R907.3 No more than two layers of roofing are allowed. CABO allowed 3 layers. Loose fill, blown or sprayed insulation - Page 311 - Section N1101.4.1 This section requires certification of R-value, installed thickness, settled thickness, coverage area and number of bags of insulation. It also requires depth markers with inches for each 300 square feet in the attic. The old Model Energy Code had no provisions for this. 5
R-value certificate - Page 311 - Section N1101.8 This code requires a permanent certificate to be posted on or near the electrical distribution panel listing the predominant R-values for insulation including duct insulation and listing U-factors and SHGC for fenestration (glass) and listing the type and efficiency of the HVAC and water heating units. Insulation - Page 319 - Table N1102.1 Amended IRC now requires R-13 for walls and floors. Previously R-11 was acceptable. Duct insulation - Page 321 - Section N1103.2.1 Amended section requires ducts in crawl or attic to have R-6 insulation. CABO required R-4.2. Appliance vent termination - Page 349 - Section M1804.2.6 Power exhauster (not direct vent) terminations are required to be at least 10 feet from lot lines and adjacent buildings. CABO had no provisions for this. Log lighters - Page 418 - Section G2433.1 Log lighters must be listed and marked as complying with CSA 8 standard and manufacturers installation instructions must be on site. CABO had no provisions allowing log lighters. Plumbing test - Page 426 - Section P2503.6 This code changed the air test on supply piping to 50 PSI. CABO required 75 PSI. Radon Control - Page 601 - Appendix F This section specifically adopts the appendix on radon control methods that require radon-resistant construction and a passive depressurization system. This will include a 3 pipe from under a slab or membrane extending into the attic and only through the roof if tests show radon. All potential entry points in floors and foundation walls must be sealed. A radon system is not required in crawl spaces with mechanical ventilation or other approved system. This was not previously adopted. This document is available online at www.knoxcounty.org/codes. 6