Waterproofing and Backfilling

Welcome to the BuildBlock ICF Installer Training Series: Waterproofing and Backfilling. This 20 part video series is intended to be an educational walk through of the ICF building process. From the early planning phases to pouring concrete and finishing walls, this series will provide the basic knowledge you need to have a successful BuildBlock ICF build.

In video number 17 we help you understand the importance or proper waterproofing as well as the challenges associated with backfilling against an ICF wall.

The videos in this series are produced as a companion to the BuildBlock Installation and Technical Manuals available for free download on the Publications Page or for purchase via the BuildBlock Online Store. You can view more videos in this series via the BuildBlock Blog or by subscribing to the BuildBlock YouTube Page. For a more in depth training experience you can take the free Online ICF Installer Training Series.

Video Transcript

Waterproofing and Backfilling

This video will help you understand the importance of proper waterproofing and the challenges associated with backfilling against an ICF wall. BuildBlock also publishes a Comprehensive Guide to ICF Waterproofing on its website and recommends anyone who is building a below grade structure review it.

Building codes require that walls below grade with an interior enclosed space that is habitable be sufficiently waterproofed. Many types of waterproofing may be used by themselves or in combination.

The primary methods of waterproofing are peel and stick membranes, dimpled drainage mats that are fastened to the ICF walls, and liquid systems that are either sprayed, rolled, or applied with a trowel.

Self-adhesive waterproof membranes such as Tamko TW-60 are placed vertically and overlapped to prevent water intrusion from the surrounding soil.

Air Gap membranes such as DMX-AG are dimple boards that are placed with the dimples against the ICF to allow water to rise and fall from the bottom to the top. This displaces air and reduces hydrostatic pressure against the wall. Air Gap membranes also offer some limited protection of underlying ICF waterproof membranes when backfilling.

Spray on membranes for ICF are growing in popularity as well, but currently depend on regional skills and the availability of applicators. Newer methods are designed to save labor and material cost.

Basic Installation

The steps below cover the basic process behind installing ICF waterproofing. Review the BuildBlock Installation Manual and the Comprehensive Guide to ICF Waterproofing for in depth installation strategies. Think of waterproofing an ICF basement like building a swimming pool, but keeping the water on the outside.

When installing waterproofing first clean or scrub the block face thoroughly clear of debris and remove any yellowing from UV breakdown. Walls must be free of all oxidation and debris so use a hose with a broom or brush to wash the walls.

Fill any major openings in the foam surface and then rasp flush with the foam surface. It is recommended to apply an ICF primer to help the adhesive stick.

Precut the waterproofing membrane for lengths of the entire wall height plus 12 inches above grade and an additional 4 inches for the base. Attach the membrane to the wall beginning 1 inch above backfill grade and roll downward overlapping 4 inches and terminating 4 to 6 inches over the footing.

Only remove 12 inches of the backing at a time from the top working down as you attach the membrane to the wall. Work slowly as to not damage the membrane and eliminate air bubbles working down the wall.

When the membrane is installed, secure the top of the membrane with a thin metal strip to keep it from releasing from the wall. It’s important to ensure that construction debris does not get behind the membrane.

Use an adhesive caulk such as NP1 to seal the membrane against the concrete. It’s also very important to seal the bottom edge, use the same adhesive caulk at the metal strip to ensure this is done thoroughly.

Use an ICF friendly mastic such as Hydrocide 800 B to cover all terminations and edge seams in the membrane. Do this on the top, sides, and outside of all seams, but not underneath the seam. Follow manufacturing installation instructions to attach a protection mat such as DMX at the top of the wall. This prevents damage from backfill material which could punch or tear holes in the membrane.

Do not screw into the membrane to attach the DMX or platon products to the wall unless above grade only. Instead use mastic with a trowel, spaced one foot apart, as an adhesive to stick the DMX or platon to the wall. Overlap the dimples in these products and lock the edges together. Extend the drainage mat to the edge of the footing so water is shed to the foundation drainage system. Use mastic to secure the bottom of the material to the wall evenly every few feet, but not continuously, and backfill as soon as possible once the floor system is in place. Do not backfill any below grade structure until the floor system is in place.

It’s important to backfill quickly since heavy winds can damage this installation. Be cautious when backfilling not to pull down the platon or DMX.

Visit buildblock.com and download the BuildBlock Installation & Technical Manual and the Comprehensive Guide to ICF Waterproofing for more information.