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HomeMy WebLinkAboutPlan RevisionsMove existing utilities & appliances to new utility I{emov'e existing wall for hallwa' //to existing door & to new Ent y wall, / outhSidelight Hallway 106 3'_6„ .11= Aemove,existing wal1/, r / / i /,/ / // ,/ / / ' 1 / • / / La Porch 112 0 C iee-3,47-1/5 1911-457L P V e 1/3////,0 10' SUBJECT TO NOTED EXCEPTIONS & INSPECTIONS GARFIELD COUNTY IB JILD DEP T: Date3�/ A By LD COPY NO INSPECTION WITHOUT THESE PLANS ON SITE page of Blue Ox Logcrafters PO Box 644 Carbondale, CO 81623 Ph & Fax: (970) 963-3689 infoablueoxloecrafters.com www.blueoxloecrafters.com Project: Short Addition Description: New Dormer Floor Plan Sheet No: A1.011 partial flare• 3/R/11 [Scale: 1 /4" = 1' -fl" —/0 -- /S/G .7,4�lce- cep,)' h_ A -Loi 1 149 Blue Ox Logcrafters PO Box 644 Carbondale, CO 81623 Ph & Fax: (970) 963-3689 info blueoxlokcrafters.com www.biueoxlaecrafters.com Project: Short Addition Description: New Dormer RFC Plan Sheet No: A1.0/3artial Date. 3/R/1 1 'Scale: 1 /4" = 1"-0" Exist. N w entry dormer New r new window sizes —/ 2426 111 Blue Ox Logcrafters PO Box 644 Carbondale, CO 81623 Ph & Fax: (970) 963-3689 infoCu.blueoxloecrafters.com www.blueoxloacrafters.com Project: Short Addition Description: New Dormer East Elevation Sheet No: A2.0/1 partial Date.. 1/R/11 1 Scale: 1 /4" = 1'-(1" r nolithic slab with 16" footing ge. Verify In Field, match existing. d thickened edge with 4" x 12" at 18" o.c. d edge meets existing, wall with 16" footing l 52.0 1 4 1 2 2'-7" 10' 5' J 1'-4" 3'x3'x l' pad with (4) #5 rebar both ways 10" pier with 20" Bigfoot footer and (3) #4 rebar (b.o. footer min 36" below finish grade) 12'-3" porch/dormer support eV"! Size soffit -*4e. 543folded avid 6611 - bpi «-') i ' re6,w, 40. Blue Ox Logcrafters PO Box 644 Carbondale, CO 81623 Ph & Fax: (970) 963-3689 info(iblueoxloecrafters.com www.blueoxloacrafters.com Project: Short Addition Description: New Dormer Foundation Plan Sheet No: 51.0/1artial in�t� 3N/11 [Scale: 1/4" = 1'-(}" ti Scale: 1/4" = 1'-0" Lagscrew all log to log connections min. 6" embedment Toe -lag log column to beam (3) 2x8 pressure treated PB46 1 (2) 2x8 pressure treated 1/2" x 6" lagscrew (typ) finish grade 10" pier with (3) #4 rebar Side Elevation 20" 'Bigfoot' footer Blue Ox Logcrafters PO Box 644 Carbondale, CO 81623 Ph & Fax: (970) 963-3689 infoObiueoxloecrafters.com www.blueoxtoecrafters.corn Project: Short Addition Description: Entry Porch found/framing detail Sheet No: S2.0/1 nate. 3/R/11 David Bartholomew From: Blue Ox Logcrafters [info©blueoxlogcrafters.comi Sent: Thursday, October 14, 2010 5:22 PM To: David Bartholomew Subject: Short addition questions Attachments: shortSl.1 found.pdf; shortA1.1 floor.pdf; shortA2.1 east.pdf; shortA2.2 north.pdf; shortA3.3 wall.pdf Dave, Attached are screenshots of a floor plan, elevations, wall section, and foundation plan for an addition we are planning for the Short residence in Silt. If you want to print, they are in 118" scale (1/2" on wall section). Choose page scaling:none. The original house is on 3' stem walls/footers and the new addition is going on an existing monolithic slab which was poured at the time of the original construction (Building Permit #6954, 10127198). The existing slab is 18" below finish floor and so we have a unique situation where we have a concrete slab instead of earth below the joists and only a 7" crawl - space. Questions are as follows: 1. Will we need to vent the so-called craw -space and if so, do we need to meet the IRC requirements of sq. inch per 150 sq. ft.? Ye S 2. Since we are insulating the floor joist cavity, do we need to excavate and insulate the slab perimeter per Garfield County and IRC specs? This would be a major issue if so and we hope to avoid it. I am concerned about added costs and existing under -slab gravel slumpage during excavation and backfilling. Pe Pvtcrwee gete2440,,e44dilheyi 3. Any vapor barriers suggested between slab and framing or bottom of joists? P &iijti ~er1f4b ln5f4114b e 4. Does the county have on file the original slab specs and inspection notes? We are lacking those to some degree. pecheru nevi/ow – p,. ve cry fico a 'ner. 5. Can we get signed off on the original slab without inspection?_excavations/core samples? rf/4eeT Guirr tCz�raAdn — rr s/Av, ' ion 6. Would there be an existing soils report on file with the county? Roger Sherman Blue Ox Logcrafters Phone & Fax: 970.963.3689 Cell: 970.618.2610 www.blueoxloqcrafters.com 1 co,f/1/ • VA II i (1) a Li I 4 # i i Q 1 9 9 s;d115r19 ta,nda ion 5) Wall Section '1•• vM - +• _ rc 1 1 1 1 1 1 4 1 L _ _ _ L 1 1 i ROOF -CEILING CONSTRUCTION This wetting and drying action will cause rotting and decay. To avoid this, the attic must be ventilated to pre- vent the accumulation of water on building compo- nents. The installation of a vapor retarder acts to pre- vent the passage of moisture to the attic, and an effective vapor retarder allows a decrease in ventila- tion. Vapor retarders are ineffective when openings in the barrier allow moisture to be carried by air into the attic. This is also the reason exhaust fans must termi- nate outdoors and not in the attic. Care should be ex- ercised to assure that attic vent openings remain un- obstructed. To minimize condensation problems within attic and enclosed rafter spaces, free-flow ventilation of such spaces is required. Ventilation openings must be screened to prevent the entry of animals. Ventilation openings requiring cutting or notching of the roof fram- ing member must comply with Section R802.7. R806.2 Minimum area. The total net free ventilating area shall not be less than 11150 of the area of the space ventilated except that reduction of the total area to'/3,pp is permitted pro- vided that at least 50 percent and not more than 80 percent of the required ventilating area is provided by ventilators located in the upper portion of the space to be ventilated at least 3 feet (914 mm) above the eave or cornice vents with the balance of the required ventilation provided by eave or cornice vents. As an alternative, the net free cross -ventilation area may be reduced to 14, when a Class I or 11 vapor barrier is installed on the warm -in -winter side of the ceiling. •. The attic vent size required by the code should not be overlooked. The net -free area can be as much as 50 percent less than the gross opening area. For exam- ple, one manufacturer's 24 -inch square (610 mm) ga- ble vent [gross area equals 576 square inches (0.37 m2)] is listed in their catalog as having a net free area of 308 square inches (0.20 m2), which is about 53 per- cent of the gross area. The manufacturer's literature should be consulted to obtain free -area information. R806.3 Vent and insulation clearance. Where eave or cornice vents are installed, insulation shall not block the free flow of air. A minimum of a 1 -inch (25 mm) space shall be provided between the insulation and the roof sheathing and at the loca- tion of the vent. :• Vent openings must be maintained clear, and they must not block the free flow of air; therefore, the code requires that insulation be held back from the vent opening a minimum of 1 inch (25 mm). The 1 -inch (25 mm) clearance must be maintained not only at the vent but throughout the attic and rafter spaces. R806.4 Unvented attic assemblies. Unvented attic assemblies. (spaces between the ceiling joists of the top story and the roof rafters) shall be permitted if all the following conditions are met: 1. The unvented attic space is completely contained within the building therrnaI envelope. 2. No interior vapor retarders are installed on the ceiling side (attic floor) of the unvented attic assembly. 3. Where wood shingles or shakes are used, a minimum 1/4 inch (6 mm) vented air space separates the shingles or shakes and the roofing underlayment above the structural sheathing. 4. In climate zones 5, 6, 7 and 8, any air -impermeable insu- lation shall be a vapor retarder, or shall have a vapor retarder coating or covering in direct contact with the underside of the insulation. 5. Either Items 5.1, 5.2 or 5.3 shall be met, depending on the air permeability of the insulation directly under the struc- tural roof sheathing. 5.1. Air -impermeable insulation only. Insulation shall be applied in direct contact with the under- side of the structural roof sheathing. 5.2. Air -permeable insulation only. In addition to the air -permeable installed directly below the struc- tural sheathing, rigid board or sheet insulation shall be installed directly above the structural roof sheathing as specified in Table R806.4 for condensation control. 5.3. Air -impermeable and air -permeable insulation. The air -impermeable insulation shall be applied in direct contact with the underside of the struc- tural roof sheathing as specified in Table R806.4 for condensation control. The air -permeable insulation shall be installed directly under the air -impermeable insulation. ❖ Unvented attics are attics where the insulation and air barrier boundary are moved to be directly above the attic space, instead of on top of the ceiling. Unvented attics eliminate the extreme temperatures of the attic, thereby placing the HVAC, ducts, pipes, and anything in the attic space into a more favorable environment. Unvented at- tics increase energy efficiency and decrease wear and tear on equipment in the attic. This section describes at- tics where the insulation and air barrier are above in- stead of below the attic space. Moving the insulation and placing an air -impermeable barrier above the attic mod- erates attic conditions so they are similar to the condi- tions of the residential space below. The primary benefit of having the insulation and air barrier above the attic is that ducts and/or HVAC equipment in the attic are not de- livering cooled air through a hot summer attic and heated air through a cold winter attic. Another benefit is to elimi- nate the attic vents that sometimes allow moisture to condense inside the attic, admit rain during extreme weather and possibly admit sparks in fires. Because this space is inside the building's thermal en- velope, the traditional attic ventilation required by Sec - /tions R806.1 and R806.2 is not required. Unvented attics require water/moisture control. Water moves in (or out) of buildings three main ways. The greatest amount of moisture is moved as bulk water (rain or any kind of wa- ter flow). Less moisture is moved by moving moist air, such as with infiltration. The least amount of moisture is moved by moisture migration through materials. As with any attic, the roof itself is the main barrier for keeping wa- ter from entering the attic. 8-70 2009 INTERNATIONAL RESIDENTIAL CODE® COMMENTARY ROOF -CEILING CONSTRUCTION protection from ignition (Section R316.5.3). See the commentary for Sections R302.10 and R316 for a complete discussion regarding these requirements and the options available. Ducts in this unvented attic construction would be considered as being inside the building thermal envelope and would not require insu- lation (see Section N1103.2.1). The provisions of this section consider the attic as- sembly as a "conditioned" space; there is no require- ment for the space to be provided with conditioned air supply. The attic space is considered indirectly condi- tioned because of omission of the air barrier, insulation at the ceiling and leakage around the attic access opening. An attic assembly complying with Section R806.4 will generally fall within the temperature ranges specified in the definition of "Conditioned space." The key concept of this section is to move the ther- mal envelope (insulation) above the attic, resulting in the attic being in a conditioned (or sometimes semi -conditioned) space. Direct air supply to the attic is not required if the attic floor is not insulated; the attic temperature would be similar to interior conditioned spaces. Ducts and/or HVAC equipment in the attic also help moderate the attic conditions. SECTION R807 ATTiC ACCESS R807.1 Attic access. Buildings with combustible ceiling or roof construction shall have an attic access opening to attic areas that exceed 30 square feet (2.8 m2) and have a vertical height of 30 inches (762 mm) or greater. The vertical height shall be measured from the top of the ceiling framing members to the underside of the roof framing members. The rough -framed opening shall not be less than 22 inches by 30 inches (559 mm by 762 mm) and shall be located in a hallway or other readily accessible location. When located in a wall, the opening shall be a minimum of 22 inches wide by 30 inches high. When the access is located in a ceiling, minimum unobstructed headroom in the attic space shall be 30 inches (762 mm) at some point above the access measured vertically from the bottom of ceiling framing members. See Section M1305.1.3 for access requirements where mechanical equip- ment is located in attics. •i• The requirement for an attic access is predicated on the likelihood that during the life of the structure, ac- cess to an attic space for repair of piping, electrical and mechanical systems will be required. Bibliography The following resource materials are referenced in this chapter or are relevant to the subject matter addressed in this chapter. AFPNNDS-05, National Design Specification (NDS) for Wood Construction—with 2005 Supplement. Wash- ington, DC: American Forest and Paper Association, 2005. AFPA 93, Span Tables for Joists and Rafters. Washing- ton, DC: American Forest and Paper Association, 1993. AiSI S100-07, North American Specification for Design of Cold -formed Steel Structural Members. Washing- ton, DC: American Iron and Steel institute, 2007. AIS 15214-07, North American Standard for Cold -formed Steel Framing -truss. Washington, DC: American Iron and Steel institute, 2007. ANSiIAITC A 190.1-07, Structural Glued Laminated Tim- ber. Centennial, CO: American Institute of Timber Construction, 2007. ANSI/TPI 1-2002, National Design Standard for Metal -plate -connected Wood Truss Construction. Madison, WI: Truss Plate Institute, 2002. APA E30-03, Engineered Wood Construction Guide. Ta- coma, WA: APA -The Engineered Wood Association, 2003. ASCE/SEI 7-05, Minimum Design Loads for Buildings and Other Structures. Reston, VA: American Society of Civil Engineers/Structural Engineering institute, 2005. ASTM D 2898-04, Test Methods for Accelerated Weath- ering of Fire -retardant -treated Wood for Fire Testing. West Conshohocken, PA: ASTM International, 2004. ASTM D 3201-07, Test Method for Hygroscopic Proper- ties of Fire -retardant Wood and Wood -base Products. West Conshohocken, PA: ASTM International, 2007. ASTM D 3737-07, Practice for Establishing Allowable Properties for Structural Glued Laminated Timber (Glulam). West Conshohocken, PA: ASTM Interna- tional, 2007. ASTM D 3957-06, Standard Practices for Establishing Stress Grades for Structural Members Used in Log Buildings. West Conshohocken, PA: ASTM Interna- tional, 2006. ASTM E 84-07, Test Method for Surface Burning Char- acteristics of Building Materials. West Conshohocken, PA: ASTM International, 2007. West Conshohocken, PA: ASTM International, 2007. DOC PS 1-07, Structural Plywood. Washington, DC: United States Department of Commerce, National In- stitute of Standards and Technology, 2007. DOC PS 2-04, Performance Standard for Wood -Based Structural -Use Panels. Washington, DC: United States Department of Commerce, National Institute of Standards and Technology, 2004. DOC PS 20-05, American Softwood Lumber Standard. Washington, DC: United States Department of Com- merce, National institute of Standards and Technol- ogy, 2005. IBC -09, international Building Code. Washington, DC: International Code Council, Inc., 2009. 8-72 2009 INTERNATIONAL RESIDENTIAL CODE® COMMENTARY 4. Expansion Index greater than 20, determined in accor- dance with ASTM D 4829. •:•This section defines "expansive soil" as any plastic material with a PI of 15 or greater with more than 10 percent of the soil particles passing a No. 200 sieve and less than 5 micrometers in size. As an alternative, tests in accordance with ASTM D 4829 can be used to determine whether a soil is expansive. The expansion index is a measure of the swelling potential of the soil. R403.2 Footings for wood foundations. Footings for wood foundations shall be in accordance with Figures R403.1(2) and R403.1(3). Gravel shall be washed and well graded. The maxi- mum size stone shall not exceed 3/4 inch (19.1 mm). Gravel shall be free from organic, clayey or silty soils. Sand shall be coarse, not smaller than'/16-inch (1.6 mm) grains and shall be free from organic, clayey or silty soils. Crushed stone shall have a maximum size of 1/2 inch (12.7 nun). + See Figures R403.1(2) and R403.1(3) and refer to the commentary for Section R401.1. R403.3 Frost protected shallow foundations. For buildings where the monthly mean temperature of the building is main- tained at a minimum of 64°F (18°C), footings are not required to extend below the frost line when protected from frost by insula- tion in accordance with Figure R403.3(1) and Table R403.3(1). Foundations protected from frost in accordance with Figure R403.3(1) and Table R403.3(1) shall not be used for unheated spaces such as porches, utility rooms, garages and carports, and shall not be attached to basements or crawl spaces that are not main- tained at a minimum monthly mean temperature of 64°F (18°C). Materials used below grade for the purpose of insulating foot- ings against frost shall be labeled as complying with ASTM C 578. •:• This section provides an alternative method of protect- ing foundations against frost heave, thus allowing FOUNDATIONS foundations to be constructed above the frost line. Frost -protected foundations use insulation to reduce the heat loss at the slab edge. By holding heat from the dwelling in the ground under the foundation, the insula- tion, in effect, raises the frost line around the foundation. The provisions require that the building be heated and that insulation be installed in accordance with the criteria specified in Figure R403.3(1) and Table R403.3(1) based on the air -freezing index established by Figure R403.3(2) or Table R403.3(2). As Figure R403.3(1) illustrates, these provisions apply only to slab -on -ground floors. Frost -protected shallow foun- dation (FPSF) designs for heated buildings are not to be used for unheated spaces. The provisions also pro- hibit the attachment of additions with FPSF to base- ments or crawl spaces that are not heated because, al- though unlikely, in very cold climates frost could penetrate under FPSFs from unheated basements or ventilated crawl spaces. The insulation values speci- fied in this section are only for the purposes of exercis- ing this option, and the Chapter 11 energy conserva- tion provisions could result in slab -edge insulation with a greater degree of thermal resistance. Conversely, if slab -edge insulation is used to comply with Chapter 11, a builder may take advantage of that insulation to reduce the foundation depth in accordance with this section. R403.3.1 Foundations adjoining frost protected shallow foundations. Foundations that adjoin frost protected shallow foundations shall be protected from frost in accordance with Section R403.1.4. •;•This section requires that foundations that adjoin FPSFs be protected from frost according to the current requirements of Section R403.1.4, which requires that foundations extend below the frost line, be built on TABLE R403.3(1) MINIMUM FOOTING DEPTH AND INSULATION REQUIREMENTS FOR FROST -PROTECTED FOOTINGS IN HEATED BUILDINGS° AIR FREEZING INDEX (°F-days)e MINIMUM FOOTING DEPTH, D (Inches) VERTICAL INSULATION FI -VALUE'' ° HORIZONTAL INSULATION R -VALUE',' HORIZONTAL INSULATION DIMENSIONS PER FIGURE R403.3(1) (inches) Along walls At corners A B C 1,500 or less 12 4.5 Not required Not required Not required Not required Not required 2,000 14 5.6 Not required Not required Not required Not required Not required 2,500 16 6.7 1.7 4.9 12 24 40 3,000 16 7.8 6.5 8.6 12 24 40 3,500 16 9.0 8.0 11.2 24 30 60 4,000 16 10,1 10.5 13.1 24 36 60 a, Insulation requirements are for protection against frost damage in heated buildings. Greater values may be required to meet energy conservation standards. b. See Figure R403.3(2) or Table R403.3(2) for Air Freezing Index values. c. Insulation materials shall provide the stated minimum R -values under long-term exposure to moist, below -ground conditions in freezing climates. The following R -values shall be used to determine insulation thicknesses required for this application: Type I1 expanded polystyrene -2.4R per inch; Type IV extruded polysty- rene -4.5R per inch; Type VI extruded polystyrene -4.5R per inch; Type IX expanded polystyrene --3.2R per inch; Type X extruded polystyrene -4.5R per inch. d. Vertical insulation shall be expanded polystyrene insulation or extruded polystyrene insulation. e. Horizontal insulation shall be extruded polystyrene insulation. ' • This table provides the required R -value of horizontal and vertical insulation based on the air -freezing index. In addi- tion, it gives the minimum footing depth and the plan dimensions required for the horizontal insulation in Figures R403.3(1) and R403.3(3) (see commentary, Sections R403.3 and R403.3.1.1). 2009 INTERNATIONAL RESIDENTIAL CODE® COMMENTARY 4-17 accordance with Figure 403.3(3) and Table R403.3(1) and be continuous through the foundation of the un- heated structure. The vertical wall insulation must ex- tend between the FPSF and the adjoining slab founda- tion, and any required horizontal insulation must be continuous through any foundation walls adjoining the FPSF. No frost penetration or differential movement occurred with this construction in a HUD demonstra- tion in Fargo, North Dakota. Deep foundations of un- heated garages have been attached to hundreds of other buildings built on FPSFs in the U.S. In most cases the FPSF insulation has been placed continu- ously between the garage floor and the house FPSF; however, the insulation has not been continuous through the foundation walls of the unheated struc- tures. In these buildings, no differential movement be- tween the deep and shallow foundations has been re- ported. Insulation passing through a foundation wall must comply with the requirements of Section R403.3, i.e., it must meet ASTM C 578 and the requirements of Table R403.3(1), and the insulation must be of a type that has sufficient compressive strength to carry the load of the building. Alternatively, the building must be de- signed to carry those loads over the insulation and not bear on it. R403.3.1.2 Attachment to heated structure. Where a frost protected shallow foundation abuts a structure that has a monthly mean temperature maintained at a minimum of 64°F (18°C), horizontal insulation and vertical wall insulation shall not be required between the frost protected shallow foundation and the adjoining structure. Where the frost protected shallow foundation abuts the heated structure, the horizontal insulation and vertical wall insulation shall extend along the adjoining foundation in accordance with Figure R403.3(4) a distance of not less than Dimension A in Table R403.3(1). Exception: Where the frost protected shallow foundation abuts the heated structure to form an inside corner, vertical insulation extending along the adjoining foundation is not required. :•This section stipulates that additions built on FPSFs need not be insulated where they join a heated struc- ture because heat from both structures keeps the ground from freezing. However, where the FPSF abuts the heated building, the horizontal and vertical insula- tion must extend along the adjoining foundation to pre- vent cold from intruding under the slab through the foundation wall. The dimension of the insulation is re- lated to the width of the horizontal insulation. This technique was shown to be effective by the U.S. Army Corps of Engineers Cold Regions Research and Engi- neering Laboratory (CRREL) on a FPSF addition to an airport control tower with a deep foundation in a se- vere Alaskan climate with a 13 -foot (3962 mm) frost line. An abutment at an inside corner is an exception. In this condition, both the building and the addition heat the ground, and extra insulation is not needed. FOUNDATIONS R403.3.2 Protection of horizontal insulation below ground. Horizontal insulation placed less than 12 inches (305 mm) below the ground surface or that portion of horizontal insula- tion extending outward more than 24 inches (610 min) from the foundation edge shall be protected against damage by use of a concrete slab or asphalt paving on the ground surface directly above the insulation or by cementitious board, plywood rated for below -ground use, or other approved materials placed below ground, directly above the top surface of the insulation. + This protection for the insulation prevents damage due to excavating (e.g., for landscaping purposes). R403.3.3 Drainage. Final grade shall be sloped in accordance witli Section R401.3. In other than Group I Soils, as detailed in Table R405.1, gravel or crushed stone beneath horizontal insu- lation below ground shall drain to daylight or into an approved sewer system. •) See Figure R403.3(1) and the commentary for Section R401.3. R403.3.4 Termite damage. The use of foam plastic in areas of "very heavy" termite infestation probability shall be in accor- dance with Section R318.4. ❖ Studies have shown that rigid board insulation in- stalled below grade, particularly in areas where the hazard associated with termite infestation is very heavy, creates a pathway for termites that cannot be blocked with currently available termiticide treatments. Because it provides a place for termites to burrow in areas of very heavy termite infestation probability, the foam plastic insulation must be protected as stated in Section R320.5. R403.4 Footings for precast concrete foundations. Footings for precast concrete foundations shall comply with Section R403.4. ❖ Footings for precast concrete foundations may be crushed stone or concrete complying with Section R403.4.1 or R403.4.2. R403.4.1 Crushed stone footings. Clean crushed stone shall be free from organic, clayey or silty soils. Crushed stone shall be angular in nature and meet ASTM C 33, with the maximum size stone not to exceed tlz inch (12.7 mm) and the minimum stone size not to be smaller than 1/t6 -inch (1.6 mm). Crushed stone foot- ings for precast foundations shall be installed in accordance with Figure R403.4(1) and Table R403.4. Crushed stone footings shall be consolidated using a vibratory plate in a maximum of 8 -inch lifts. Crushed stone footings shall be limited to Seismic Design Categories A, B and C. +This section prescribes the material and installation requirements for crushed stone footing to be used for precast concrete foundations, as shown in Figure R403.4(1). The soil or the interior should not be exca- vated below the elevation of the top of the footing. Crushed stone footings installed in accordance with this section are limited in use to areas of low or moder- ate seismic hazards. 2009 INTERNATIONAL RESIDENTIAL CODE® COMMENTARY 4-19 1OUNDATIONS FLOOR GIRDER .I NAILING STEEL ANGLES AND LAG BOLTS WOOD SCAB WOOD POST TOENAILS ALTERNATE USING TREATED WOOD PLATE PIER FOOTING Figure R407.3(1) COLUMN ANCHORAGE Figure R407.3(2) COLUMN ANCHORAGE SECTION R408 UNDER -FLOOR SPACE R408.1 Ventilation. The under -floor space between the bot- tom of the floor joists and the earth under any building (except space occupied by a basement) shall have ventilation openings through foundation walls or exterior walls. The minimum net area of ventilation openings shall not be less than 1 square foot (0.0929 m2) for each 150 square feet (14 m2) of under -floor space area, unless the ground surface is covered by a Class 1 4-58 FLOOR GIRDER TOENAILING TO POST / WOOD POST 40. TOENAILED INTO TREATED WOOD PLATE Figure R407.3(3) COLUMN ANCHORAGE vapor retarder material. When a Class 1 vapor retarder material is used, the minimum net area of ventilation openings shall not be less than 1 square foot (0.0929 m2) for each 1,500 square feet (140 m2) of under -floor space area. One such ventilating opening shall be within 3 feet (914 min) of each corner of the building. •: Raised floor construction results in an under -floor space, commonly referred to as a "crawl space." To control condensation within crawl space areas and thus reduce the chance of dry rot, natural ventilation of such spaces by reasonably distributed openings through foundation walls or exterior walls is required. Condensation is a function of the geographical loca- tion and climatic conditions; therefore, the depend- ence on ventilating openings through the foundation wall or exterior wall may run counter to energy conser- vation measures. The use of a vapor retarder material on the ground surface inhibits the flow of moisture from the ground surface into the crawl space and thus re- duces the need for ventilation. Commentary Figure R408.1 illustrates the use of openings through the foundation walls. R408.2 Openings for under -floor ventilation. The minimum net area of ventilation openings shall not be less than 1 square foot (0.0929 m2) for each 150 square feet (14 m2) of under -floor area. One ventilation opening shall be within 3 feet (915 mm) of each corner of the building. Ventilation openings shall be covered for their height and width with any of the following materials provided that the least dimension of the covering shall not exceed '14 inch (6.4 mm): 1. Perforated sheet metal plates not less than 0.070 inch (1.8 mm) thick. 2. Expanded sheet metal plates not less than 0.047 inch (1.2 mm) thick. 2009 INTERNATIONAL RESIDENTIAL CODE® COMMENTARY 3. Cast-iron grill or grating. 4. Extruded load-bearing brick vents. 5. Hardware cloth of 0.035 inch (0.89 mm) wire or heavier. 6. Corrosion -resistant wire mesh, with the least dimension being '4 inch (3.2 mm) thick. Exception: The total area of ventilation openings shall be permitted to be reduced to Yo, of the under -floor area where the ground surface is covered with an approved Class I vapor retarder material and the required openings are placed to provide cross ventilation of the space. The instal- lation of operable louvers shall not be prohibited. s Installing a covering material over the ventilation open- ing keeps animals such as rodents or vermin from en- tering the crawl space. Several options are provided and they all must have openings that have no dimen- sion exceeding 1/4 inch (6.4 mm). The area of the venti- lation opening accounts for net free area of the cover- ing material used to protect the ventilation opening. For some covering materials the net free area can be up to 50 percent less than the gross area of the ventila- tion opening. The use of a vapor retarder material on the ground surface inhibits the flow of moisture from the ground surface into the crawl space and thus reduces, if not virtually eliminates, the need for ventilation. Therefore, the exception provides for a drastic reduction in the amount of ventilation openings required. While the va- por retarder may significantly reduce the moisture ac- cumulation, ventilation openings are still required but may be equipped with manual dampers to permit them to be closed during the coldest weeks of the year in FOUNDATIONS northern climates. The following is an example of the area calculation: Example 1: A house has a crawl space area of 1,300 square feet (121 m2). The amount of ventilation opening re- quired is 1,3001150 = 8.7 square feet (0.805 m2) x 144 square inches per square foot = 1,252 square inches (0.81 m2). This is the total net clear area of opening required that must be distributed among all the openings. An 8 -inch by 16 -inch (203 mm by 406 mm) opening provides 128 square inches (0.83 m2). Ten 8 by 16 -inch (203 mm by 406 mm) openings will provide 1,280 square inches (0.83 m2) which is greater than the 1,252 square inches (0.81 m2) required. The following is an example of using the exception: Example 2: In Example 1, the required amount opening area (1252 square inches) may be reduced by a factor of 10 to125.2 square inches (80 826 mm2) if an ap- proved Class I vapor retarder is used on the ground surface of the crawl space in accordance with the exception. Note that opening placement must pro- vide cross ventilation. R408.3 Unvented crawl space. Ventilation openings in under -floor spaces specified in Sections R408.1 and R408.2 shall not be required where: 1. Exposed earth is covered with a continuous Class I vapor retarder. Joints of the vapor retarder shall overlap by 6 inches (152 mm) and shall be sealed or taped. The edges 18 IN. X 24 IN. MIN ACCESS HOLE 3 FT MAX (TYP FROM CORNERS) SCREENED OPENINGS (MESH OPENING>_ 1/8 IN.) THROUGH FOUNDATION WALL TO CRAWL SPACE TOTAL NET CLEAR AREA OF OPENING EQUALS THE CRAWL SPACE AREA DIVIDED BY 150 For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm. Figure R408.1 CRAWL -SPACE VENTILATION 3 FT 2009 INTERNATIONAL RESIDENTIAL CODE® COMMENTARY 4-59 ' OUNDATIONS of the vapor retarder shall extend at least 6 inches (152 mm) up the stem wall and shall be attached and sealed to the stem wall; and 2. One of the following is provided for the under -floor space; 2.1. Continuously operated mechanical exhaust ven- tilation at a rate equal to 1 cubic foot per minute (0.47 Lis) for each 50 square feet (4.7m2) of crawlspace floor area, including an air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accor- dance with Section 141102.2.9;. 2.2. Conditioned air supply sized to deliver at a rate equal to 1 cubic foot per minute (0.47 L/s) for each 50 square feet (4.7 m2) of under -floor area, including a return air pathway to the common area (such as a duct or transfer grille), and perim- eter walls insulated in accordance with Section N1102.2.9; 2.3. Plenum in existing structures complying with Section M1601.5, if under -floor space is used as a plenum. +This section lists several conditions under which the ventilation openings through the foundation walls are not required. The exposed earth of the under -floor area must be covered with a continuous Class I vapor retarder. See the commentary Section R202 for vapor retarder class. If the perimeter walls are insulated, ei- ther a continuously operating mechanical exhaust vent or conditioned air must be provided in order to eliminate the ventilation openings. Elimination of the ventilation openings is permitted in existing structures when the under -floor space is used as a plenum. Under -floor plenums are prohibited in new construction (see commentary, Section M1601.5). R408.4 Access. Access shall be provided to all under -floor spaces. Access openings through the floor shall be a minimum of 18 inches by 24 inches (457 mm by 610 mm). Openings through a perimeter wall shall be not less than 16 inches by 24 inches (407 mm by 610 mm). When any portion of the through -wall access is below grade, an areaway not less than 16 inches by 24 inches (407 mm by 610 mm) shall be provided. The bottom of the areaway shall be below the threshold of the access opening. Through wall access openings shall not be located under a door to the residence. See Section M 1305.1.4 for access requirements where mechanical equipment is located under floors. ❖ The provisions of this section require access to all un- der -floor spaces. Access is required for continuing maintenance of the building and for inspection and re- pair of such items as plumbing, mechanical systems or electrical system runs within the crawl space. This section addresses the different conditions encoun- tered in accessing an under -floor space through the floor system or the foundation wall. Where the access opening is through the floor, an opening of not less than 18 inches by 24 inches (457 mm by 610 mm) is required. Where the access opening is through the foundation wall, an opening of not less than 16 inches by 24 inches (406 mm by 610 mm) is required. See Commentary Figure R408.1. The 16- and 24 -inch (406 mm and 610 mm) dimensions are to work with stan- dard CMU coursing. Where mechanical equipment is located under the floor, the minimum access opening must comply with Section M1305.1.4. R408.5 Removal of debris. The under -floor grade shall be cleaned of all vegetation and organic material. All wood forms used for placing concrete shall be removed before a building is occupied or used for any purpose. All construction materials shall be removed before a building is occupied or used for any purpose. ❖ Vegetation, stumps, roots and other matter left in an excavation around a building are major causes of ter- mite infestation and moisture problems. As such mate- rial decays, the ground settles, negating the original drainage plan. Even before decay, the material pro- vides pockets for water accumulation, which can have subsequent destructive impact on the structure. To eliminate a natural attraction to termites, insects or an- imals, all vegetation and organic material must be cleared. R408.6 Finished grade. The finished grade of under -floor surface may be located at the bottom of the footings; however, where there is evidence that the groundwater table can rise to within 6 inches (152 mm) of the finished floor at the building perimeter or where there is evidence that the surface water does not readily drain from the building site, the grade in the under -floor space shall be as high as the outside finished grade, unless an approved drainage system is provided. +To circumvent moisture accumulation in the crawl space area, the grade in the under -floor space must be at the same elevation as grade outside of the building if the groundwater table can rise to within 6 inches (152 mm) of the finished floor elevation or the surface water does not readily drain from the site. An alterna- tive would be an approved drainage system. R408.7 Flood resistance. For buildings located in areas prone to flooding as established in Table R301.2(1): 1. Walls enclosing the under -floor space shall be provided with flood openings in accordance with Section R322.2.2. 2. The finished ground level of the under -floor space shall be equal to or higher than the outside finished ground level on at least one side. Exception: Under -floor spaces that meet the requirements of FEMA/FIA TB 11-1. To minimize hydrostatic loads by allowing the free in- flow and outflow of floodwaters, buildings in flood haz- ard areas (A Zones) that have walls enclosing under- floor spaces are to have flood openings in those walls. This provision alerts the designer that flood openings are to be provided in addition to standard ventilation openings. This requirement applies only to buildings in 4-60 2009 INTERNATIONAL RESIDENTIAL CODE° COMMENTARY