Fire-rated wall construction components and wall systems for use in building construction. Embodiments can include tracks for holding studs which incorporate various geometries capable of receiving fire-retardant material, including but not limited to intumescent material. The fire-retardant material can be attached to compressible backer rods inserted within deflection gaps in the wall systems such that the fire-retardant material expands and seals gaps and/or areas between the tracks and wall components such as ceilings, floors, and drywall. Various assemblies and methods can be used to cover the deflection gap.