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Home My WebLink About; La Costa Valley Units 1 & 2; Recommendations for Footings; 1964-12-08- - - - ,- - .- - - - - - PHlLlP “(ENKING BENTON .wzS,M”T CIYIL IYc.I”=L” BENTON ENGINEERING. INC. APPLIED SOlI. MECHANICS - FO”ND*TrcmS 674, EL CAJDN BOULE”*RD *AN DIEGO. CALIFORNIA D111S December 8, 1964 Paradise Homes, Inc. Route 1, Box 2550 Encinitm, California Attention: subiectr Mr. Irv Roston Proiect No. 64-6-18D Recommendations far Footings for Soil Conditions on. La Costa Valley Unit Nor. 1 and 2 Son Diegc County, California SAN DIEGO: 5s5-565. LA WIIA: .e*.?Ies. U& /LB-d 168-7 ~c;s;+us dc IG COX+CI fb5-6A-1 It is concluded from correlating the laboratory test results presented with our “Final Report on Compacted Filled Ground, La Costa Unit Nos. 1 and 2, San Diego County, Callfornio”, doted November 25, 1964, with the visual observationa made during grading and in classifying the soils in exploration borings drilled upon completion of grading that the soils within the upper three feet on the lots fall within two ma[or categories listed below: M?rgfnally Expansive Unit No. 1 - Lots 43 48, 49, and 52, 53, 54 s&? an 60, 72, 73, and 74, 76: ‘L”’ 79, 80, and 81, 84 to 89, inclusive 93, 95, 96, 99, 100, and 101, 106, 108, 109, 110, 111, 127, 128, and 131, Condominium Areas C and D Expansive Unit No. 1 - 59, 61 t 1, inclusive,~ 75, 77, and Lots 44, i? 46, 50, 51, 57, 58, and 78, 82, , 90, 91, and 92, 94, 97, 98, lO2 to 105, inclusive, 107, 112 to 119, Inclusive, 130, 132, and 133, Model Lots 122 to 126, inclusive, and 129, Condominium Arear A, B, E, F, H, I, and J. Unit No. 2 - Unit No, 2- Lot 139 (3-10-67) Lots 135, 136, 137 and 140 (3-1067) It is concluded from our pat experience in ares where rolls fall into these two general cate- gories that continuous wall footings should be used throughout and that thee should be placed at varying depths and reinforced ta varying degrees depending upon the volumetric change with change in molrture content of the supporting soils. Also, if concrete slabs are to be s1010 .16.27 :~ .r - - - - - - - - - - A L - - - i i - \ .. Project No. 64-6-18D La Costa Volley Unit Nos. 1 and 2 -2- December 8, 1964 pieced on the “expansive” soils, it is recommended moisture tests be taken 4 to 5 weeks prior to pouring concrete to verify that 80 percent saturation of the layers exist, to a depth of 3 feet, if less moisture exists, then presaturotion would be recommended. The reason for this is that concrete slobs ore relatively lightly loaded in comparison to continuous wall footings support- ing raised wood floors and they ore subject to much greater upward mwement if the “expansive” clays go from a relatively dry field condition to neor saturation than ore the wall footings that are placed at greater depths below the finished ground surface, Numerous tests and chservo- tions made to dote indicate that the “expansive ” soils tend to increase in moisture content with time, once these ore covered and lawn watering, etc. takes place around the perimeter of the foundation, Houses constructed in the spring when the soils have natural presoturation have proved to show for less differential movement than houses constructed on air dry soils without presoturation in the fail of the year. The-XolJowing recommfndotions are made for the two cotegroies of soils listed previously: I. Type of Construction of Raised Wocd Floors on Continuous Wall Foundations. \, \\ ‘\ ‘\ <\, i i L A. For Marginally Expansive Soil Conditions 1. Place footings at minimum depth of one foot. 2. Reinforce with one 84 steel bar placed at three (3) inches above the bottom of the continuous wall footings and one #4 steel bar placed at one and one- half (1 l/2) inches below the top of stem wall of the footing. 0 3. It is recommended that the steel reinforcement of all interior and exterior con- tinuous wall footings be lopped 48 diameters and that the reinforcement of the interior footings be carried into the exterior woils sufficient distance to de- velop full strength. 4. Construct crawl holes with continuous reinforcement as shown on page 17 of the “Minimum Prcperty Requirements fa properties of one or two Living Units, Located in the Southern California District” by the Federal Housing Adminis- ,P tration Revised May 1952 or by some equivalent design. 5. For concrete slabs on ground in the goroges, it is recommended that a 4 inch thickness of sand be placed beneath the concrete slab and that the concrete slabs be separated by 3/s inch thickness OF construction joint material from the exterior wall footings. The slobs should also be reinforced with 6”-6” by #lo-#10 wire mesh. 6. For Expansive Soil Conditims Place footings at a minimum depth of two feet. Reinforce with one N.5 steel bar placed three inches above the bottom of footing and one #5 steel bar pieced 1 l/2 inches below the top of stem wail of the footing. BENTON ENGINEERING. INC. - - - - - - :- Project No. 64-6-18D Lo Costa Valley Unit Nos. 1 and 2 -3- December 8, 1964 3, 4, and 5. Same OS for Section A above. II. Type of Construction of Concrete Slab Floors on Ground Between Continuous Wall Foundations A. For Marginally Expansive Soil Conditions 1. 2. 3. 4. 5. Place footings at a minimum depth d one foot. Reinforce tith one #4 steel bar placed at three (3) inches above the bottan of the continuous wal I footings and one #4 steel bar placed at one and one- half (1 J/2) inches below the top of stem wall of the footing. It is recommended tha; the steel reinforcement of all interior ond exterior con- tinuws wall footings be lapped 48 diameters and that the interior reinforcement be carried into the exterior walls sufficient distance to develop full strength.,, The concrete slabs on ground inside the houses should be placed on a minimum of 4 inches of sand and reinforced with 6”-6” by #lo-#10 wire mesh. A water- proofing seal under, within, or on top of slob should be provided. Far concrete slabs on ground in the garages, it is recommended that a 4 inch thickness of sand be placed beneath the concrete slob and that the concreie slabs be sepomted by 3/8 inch thickness of construction joint material from the exterior wall footings. The slobs should also be reinfaced with 6”-6” by #lo-#10 wire mesh. B. For Expansive Soil Conditions 1 Place footings at o minimum depth of two feet. 63 2. Reinforce with one #5 steel bor placed at three (3) inches above the bottom of the continuous wall footings ond one R.5 steel bar placed at one and one- half (1 l/2) inches below the top of stem wait of the footing. 0 3. I is recommended that the steel reinforcement of all interior and exterior con- inuws wall footings be lapped 48 diameters and that the interior reinforcement be carried into the exterior walls sufficient distance to develop full strength. 0 4. or concrete Slats on ground for this condition, it is recunmended that field moisture checks be made to three feet below finished grade to verif&l per- %%%%e?d&d by ponding, t80 percent soturotion is not present, then it is recanmend<d “rain birds” or any suitable method to in- crease moisture as required. After the presoturation moisture content is achieved within the upper three feet, the soil may be permitted to surface dry so that equipment may work on it and then the 4 inch sand layers should be depaited BENTON ENOINEERING. INC - - - - - - - . Project No. 64-6-18D Lo Costa Volley Unit Nos. 1 and 2 -4- Decembe.r 8, 1964 within one week. The reinforcing with 6”-6” by #IO-#10 wire mesh and woter- proofing may then be installed to seal the presaturoted soils under the concrete slabs. 0 5. For concrete slabs on ground in the goroges, it is recommended that 0’4 inch thickness d sand be placed beneath the concrete slab and that the concrete slobs be separated by 3/% inch thickness of construction joint material frcm the exterior wall footings. The slabs should also be reinforced with 6”-6” by #IO-#10 wire mesh. I If you should hove any questions regarding the above, or if you should desire additional infor- moticn, please feel free to contact me. Very truly yours, BENTON ENGINEERING, INC. 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