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r '___"'__.._'_u.__" _,""-___~___ .'. ... ~- FREEZING WEATHER EFFECTS ON BUILDING CONSTRUCTION GENERAL Bccall~C \\';11(1 c:\p;lI1ds upon freezing and soils C(mt~~jJl water, soils which arc allowed 10 freeze will heave and lose dCllsny UPOTllh;Jwlng, these soils wiHnot rcg;linlhclf original strength and dCJlsil~ The extent ofhcaveand dcn:"ily/sln.'llgllJ Joss depends on the soil lype ;Iud Illoiswrc condition. Heave is grc.JICI IS :-:ojl5 'with higher pcrcclll;.Jgc of rilles (silts/clays). High silt conlClll sojjs arc most susceptible, due 10 their ]11~11 capillary rise rOICJl1I~ll which C!I\ crc.31:;2 ice lenses. Fine gr;lll:<c ~<]o:: ~;~ncr.D.l!.'i' hC3'l!C about 1/," 10 ::/:/' (or c~.ch fOl.,! Dffr0st pcnclr;l1lOll, This cWlr.anSlatc 101"101" Ofl01;il frost he,lye This IOlaI amOUlIT Clll be sl~llj(J.canlly greater if ice lensing Occurs DESIGN CONSIDERATIONS Cl:aycy and silty soils can be used as perimeter backfilL although lhe effect of their poor dr21I1age and frost propcnics should be considered_ Basement areas will have special drainage and lateral load requirements which arc not discussed here. Frost heave may be critical in doorway areas. Stoops or sidnvalks adjacenito doorways could be designed as structural slabs suppoIied ou frost footiugs with void spaces below. With tlns design, movements may then occur between the structural slab and the adjacent on-grade slabs. Non-frost susceptible sands (with less thon 12% passing a #200 sieve) can be used below such areas. Depeudiug on the function of surrounding areas, the sand layer may need a thickness transition a,,'ay from the area where movement is critical. With saud placement over stower draining soils, subsurface drainage would be ueeded for the sand layer. High deusity extruded insulation could be used witllin tlle sand to reduce frost penetration, thereby reducing the sand thickness needed. We caution that iusulation placed near tlle sllIface can increase tlle potential for ice glazing of tlle surface The possible effects of adfreezing should be considered if clayey or silty soils are used as backfitl. Adfreezing occurs when backfill adheres to rough surfaced foundation walls and lifts the wall as it freezes and heaves. This occurreuce is most common will. masonry block walls, unheated or poorly heated building situations and clay backfill The potential is also increased where backfill soils are poorly compacted and become saturated. The risk of adfreezing can be decreased by placing a low friction separating tayer between the wall and backfill. Adfrcezing can occur on e>,..-terior piers (such as deck, fence, or similar pier footings), even if a smooth surface is provided This.is more likely in poor drainage situations where bockfill soils are poorly compacted and become saturated Additional footing embedment alldJor widened footings below the frost zones (wInch includes tensile reinforcement) can be used to resist uplift forces. Specific designs would reqmre individual analysis. CONSTRUCTION CONSIDERATIONS' Foundations, slabs and other improvements which may be affected by frost movements should be insulated from frost penetration during freezing weather. If filling takes place during freezing weather, all frozen soils, snow and ice should be stripped from areas to be filled prior to new fill placement The'new fill should not be allowed to freeze during transjt~ placement or compaction. This should be considered in the projec( scheduling, budgeting and quantily estimating. It is usually beneficial to perform cold weather earthwork operations jn small areas where grade can be attained quickly rather than working larger areas where a greater amount of frost stripping may be needed If slab subgrade areas freeze, we recommend the subgrade be lllawed prior to floor slab placement. The frost action may also require re\'\'orking and recompaclion of tIle thawed subgrade.