1130 RAINIER AVE WHOLE SITE DOCUMENTS 2016-01-01 MF Import

� Evereff Housing Aufhorify May 16, 2012 � JN 12080 Paga 8 assume that the backfill �vill 6e well-compacted in lifts no thicker than 12 inches. The compaction o( backiill near the walls should be accomplished with hand-operated equipment to prevent the walls from being overloaded by the higher soil forces that occur during compaction. The seclion entitled General Earfhwork and Structural Fill contains additional recommendations regarding Ihe placement and compaction of struclural flil behind relaining and fcundation walls. The above recommendations are not inlended to wa,erproof below-grade walls, cr to prevent ihe formation of mcid, milde�.v or fungi in inlerior spaces. Over time, the perfermance c` subsurface dra�rage systems can de9rade, subsurface groundwaler (!o�.� pattems can change, and utilities can break or develop leaks. �ihere(ore, avalerproofin �, should be provided where future seepagz through the �valls is not acceptable. Th:s typiczil; includes limiling cold-joints and wall penetrations, 2nd using benlonite panels or membranes on the outside of lhe walls. Thcre are a variety of different waterproofina m2terials and systems, �ahich should be installed by an experienced contractor familiar tivitli the anticipated consVuction and subsurface conditions. Applying a ihin coat of asphaif emulsion to the outside (ace of a wall is not considered v�aterproofing, and vaill only help to reduce moisture generated from water-vapor or capillary aclion from seeping lhrough the concrete. As �.vith any project, adequate ventilalion of basement and craevl space areas is important to prevent a buitd up of �vater vapor that is commonly transmitted through concrete �valls from the surrounding soil, even when seepage is nol present. This is appropriate even when waterproofing is applied to the outside of foundation and retaining �valls. We recommend thal you contact a specialty �onsultant if detailed recommendations or speci(ications related lo walerproofing design, or minimizing the potenlial for infestations of mold and mildew are desired. The Genera/, Sla6s•On-Grade, and Drainage Considerations sections should be reviewed ior additional recommendations related to the control of groundwater and excess �vater vapor for the anticipated construction. SLABS-ON-GRADE The building floor at the �vestern portion of the soulhweslern building can be constructed as a slab- on-grede atop non-organic, firm native soil or on structural fill. The subgrade soil must be in a firm, non-yielding condi(ion al the time of slab construction or underslab fill placement. Any soft areas encountered should be excavated and replaced wilh select, imported structural fill. Even where the exposed soils appear dry, water vapor wiil tend to naturally migrate upward througli the soil to Ihe new construcled space above it. This can affect moislure-sensilive ftooring, cause imperfections or damage to the slab, or simply allow excessive water vapor inlo Ihe space above the slab. All interior slabs•on•grade should be underlain by a capillary break or drainage layer consisling of a minimum 4-inch ihickness of gravel or crushed rock ihat has a fines conlent (percent passing the No. 200 sieve) of less ihan 3 percent and a sand content (percent passing the No. 4 sieve) of no more than 10 percent. As noted by the American Concrete Inslitute (�CI) in the Guides for Concrete Floor and Slab Structures, proper moisture prolection is desirable immed�alely below any on-grade slab that evill be covered by tile, evood, carpet, impermeable floor coverings, or any moisture-sensilive equipment or products. ACI also notes that vapor retarders, such as G-mil plastic sheeling, have been used in the past, bul are now recommending a minimum 10-mil thickness. A vapor retarder is defined as a material wilh a permeance of less than 0.3 perms, as delermined by ASTM E 96. It is possible ihat concrete admixtures may meet this soecification, GEOTECH CONSULT�MTS,INC.