BASC Search | Building America Solution Center

Four inches of rigid foam separate the concrete slab from the ground and the foundation walls.

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A thick vapor barrier and radon vent pipe keep soil gases out of the home.

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Wrong - Polyethylene sheeting should be lapped up sides of walls and pillars and taped

Wrong - Polyethylene sheeting should be lapped up sides of walls and pillars and taped

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Right-Polyethylene sheeting is correctly installed over aggregate and taped to pillars and foundation wall

Right-Polyethylene sheeting is correctly installed over aggregate and taped to pillars and foundation wall

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Rigid foam extends under the full slab and lines the inside edges of the foundation walls.

Rigid foam extends under the full slab and lines the inside edges of the foundation walls.

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Right - Rigid foam is installed over a waterproofing membrane that has been applied to the basement foundation walls.

Right - Rigid foam is installed over a waterproofing membrane that has been applied to the basement foundation walls.

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The home’s slab-on-grade foundation is wrapped in a blanket of rigid foam extending completely under the slab and along the edges.

The home’s slab-on-grade foundation is wrapped in a blanket of rigid foam extending completely under the slab and along the edges.

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Right – R-20 of XPS and polyiso rigid foam were added on the slab shelf that is part of this precast foundation wall system.

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Right – Workers pour the concrete for the basement floor slab over a vapor barrier installed over rigid foam.

Right – Workers pour the concrete for the basement floor slab over a vapor barrier installed over rigid foam.

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The basement is constructed with precast concrete walls lined with R-21.3 foil-faced rigid foam while an R-10 layer of XPS rigid foam covers the ground under the slab.

The basement is constructed with precast concrete walls lined with R-21.3 foil-faced rigid foam while an R-10 layer of XPS rigid foam covers the ground under the slab.

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Residential Buildings: Foundations

Reference

Website describing the U.S. Department of Energy's residential buildings program.

Polyethylene Over Aggregate

Polyethylene Over Aggregate

CAD File

2021 IECC Climate Zone 1A: Unvented Flat Roof, 2x4 Wall, Monolithic Slab on Grade

2021 IECC Climate Zone 1A: Unvented Flat Roof, 2x4 Wall, Monolithic Slab on Grade

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Right – This wall is constructed with the sill plate overhanging the top of the foundation wall so that when rigid foam is installed on the exterior of the foundation wall, its surface will align with the surface of the wall sheathing.

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Polyethylene sheeting covers the aggregate and extends down and under the footing to provide a capillary break between the ground and the slab and monolithic footing

Polyethylene sheeting covers the aggregate and extends down and under the footing to provide a capillary break between the ground and the slab and monolithic footing

CAD File

Slab-on-grade radon control techniques

Slab-on-grade radon control techniques

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A Bridge Too Far, BSI-005

Reference

Article describing thermal bridging, construction practices that encourage thermal bridging, and solutions.

Right - Basement slab with a capillary break of either gravel or a drainage mat.

Right - Basement slab with a capillary break of either gravel or a drainage mat.

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Structural system components of slab-on-grade foundation with grade beam

Structural system components of slab-on-grade foundation with grade beam

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Drainage techniques for slab-on-grade foundations

Drainage techniques for slab-on-grade foundations

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A concrete slab floor can be elevated above local grade as a strategy to prevent flood damage.

A concrete slab floor can be elevated above local grade as a strategy to prevent flood damage.

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Spray foam extends down the inside of the foundation wall to the uninsulated slab; because the wall lacked exterior perimeter drainage, the slab was cut and an interior footing drain was installed.

Spray foam extends down the inside of the foundation wall to the uninsulated slab; because the wall lacked exterior perimeter drainage, the slab was cut and an interior footing drain was installed.

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The goal of foundation moisture management is to construct the basement, crawlspace, or slab in a way that keeps moisture from getting in in the first place

The goal of foundation moisture management is to construct the basement, crawlspace, or slab in a way that keeps moisture from getting in in the first place

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Radon Fan

Guide

Guide describing how to install a radon mitigation fan to actively remove radon from the home.

Flood-Resistant Raised-Slab Foundations

Guide

Guide describing ways to construct a raised-slab foundation to increase a home's resistance to floods.

Capillary Break at Crawlspace Floor - Polyethylene Sheeting under Concrete Slab

Guide

Guide describing how to install a capillary break to help manage moisture in foundations.