Upgrade existing concrete basement floors

Tags: Finished basement, Finished basement, Foundation, Tuck under, cold, dry, hot_humid, marine, mixed_humid

A high-performing, concrete basement floor successfully manages bulk and capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. water as well as water vapor. This improves comfort in the basement living space.

If water puddles on the basement floor, drainage is required. An exterior perimeter footing drain is best, but if that’s not easily accessible, install an interior perimeter drainage system along with sump pit, and pump. Either way, each should drain to daylight, a storm sewer, or a dry wellUnderground structure that captures, then slowly releases storm-water runoff so that it can be absorbed by the soil..

If the floor shows signs of dampness or efflorescence (a white, salty deposit on the floor), the amount of moisture exceeds the interior’s ability to dry. If there’s doubt about the presence of water vapor, tape an 18-in. x 18-in. plastic square to the slab. Wait 16 hours and look for water droplets on the bottom of the plastic. In either case, additional layers should be either highly vapor permeable to allow drying or should prevent vapor transmission altogether, condensing on the underside.

If there’s adequate headroom, basement moisture can be managed by pouring a new concrete slab over the old one. If not, removing the existing floor and digging down allows you to start over. Regardless, first, install a clean stone drainage pad (a capillary break with no fines), then a vapor barrier (plastic film), followed by a layer of insulation, then the concrete slab. Follow recommended practices for detailing the slab.

Insulating beneath a concrete basement floor does more than reduce heat loss. It also lowers the relative humidity at the surface, reducing condensation, dust mites, mold, and mildew.

Test for radonColorless, odorless, short-lived radioactive gas that can seep into homes and result in lung cancer risk. Radon and its decay products emit cancer-causing alpha, beta, and gamma particles. before converting a basement into living space.

Green Points

LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. : 1/2 point available for fly ashFine particulates consisting primarily of silica, alumina, and iron that are collected from flue gases during coal combustion. Flyash is employed as a substitute for some of the portland cement used in the making of concrete, producing a denser, stronger, and slower-setting material while eliminating a portion of the energy-intensive cement required. More info or slag as replacement for 30% or more of Portland cement in foundation under MR 2.2 (Materials & Resources).

NGBSNational Green Building Standard Based on the NAHB Model Green Home Building Guidelines and passed through ANSI. This standard can be applied to both new homes, remodeling projects, and additions. /ICC-700: Under Chapter 6 — Resource Efficiency: 3 pts. for use in foundation systems, such as slabs, that are considered resource-efficient (601.8); 4 points for interior and exterior foundation perimeter drains sloped to daylight, dry well, or sump pit (602.3); up to 4 pts. for recycled-content (fly ash or slag substitution for Portland cement in concrete) (604.1). Under Ch. 7 — Energy Efficiency: up to 4 pts. for use in slabs as part of a passive solar design (704.3.1.3, 704.3.1.4).