Building Out Bugs: Sill Plate Barriers

Author, Cassie Krejci, Ph. D.
Author, Cassie Krejci, Ph.D.

Hello and welcome to discussion #9 of the TERM® Barrier System blog series! This week we will be continuing our summer blog series titled Building Out Bugs by highlighting a way you can block pests on the horizontal surface, starting with the TERM® Sill Plate Barrier.

TERM® Barriers are a collection of products that work together to complete the building envelope and block out insects. There are several products that complete the horizontal barrier for a slab-on-grade structure, including:

TERM® Sealant Barrier,

TERM® All-Pest Bath Trap Barrier,

TERM® Sill Plate Barrier, and

TERM® Flooring Underlayment Barrier.

We have talked about the TERM® Sealant Barrier and TERM® All-Pest Bath Trap Barrier in previous posts, so today we will continue with the TERM® Sill Plate Barrier.

TERM® Sill Plate Barrier is an adhesive membrane barrier designed to prevent termites from accessing wood framing members from a concrete crack or joint in the floor. TERM® Sill Plate Barrier adheres to the subfloor and blocks termite access to the sill plate. The Sill Plate Barrier may be installed under exterior and interior sill plates.

Concrete cracks and joints are one of the main access points for subterranean termites into structures. A TERM® Sill Plate Barrier installed underneath the sill plate provides 5 advantages:

  1. TERM® Sill Plate Barrier is a non-chemical barrier to subterranean termites. The barrier has been tested against termites since 2000 by Texas A&M University and is classified as a non-pesticide “barrier” by EPA regulators.
  2. TERM® Sill Plate Barrier provides a full waterproofing and vapor proofing barrier for wood framing against moisture from the concrete.
  3. TERM® Sill Plate Barrier blocks moisture and cold air from the exterior, and energy leaks from the interior.
  4. TERM® Sill Plate Barrier excludes foraging insects, such as termites and ants, from entering at gaps between the sill plate and the not-quite-level slab.
  5. TERM® Sill Plate Barrier provides supplemental protection to sodium borate treatment of wood framing.

Installation of the TERM® Sill Plate Barrier is simple.

For interior sill plates, it is ideal for the membrane barrier to overhang each side of the sill plate by 1”. This is recommended so that the sill plate barrier will tie-in to the flooring underlayment membrane, which we will discuss in the next blog post.

TERM® Sill Plate Barrier Interior Framing


TERM® Sill Plate Barrier photo

For exterior sill plates, it is recommended that the membrane barrier be 3” wider than the sill plate itself. This is to tie the TERM® Sill Plate Barrier in to the TERM® Flooring Underlayment membrane on the inside of the structure, and the TERM® Base Flashing membrane on the outside.

TERM Sill Plate Barrier Exterior Perimeter detail

TERM® Sill Plate Barrier Exterior Perimeter photo

Once all sill plates have been protected with the TERM® Sill Plate Barrier, any posts or penetrations and that fall within the area should be sealed with TERM® Sealant Barrier.

TERM® Sealant Barrier seals around penetrations TERM® Sealant Barrier is used to seal around penetrations

It’s important to note that the TERM® Sill Plate Barrier is intended for new construction.

The following is what the TERM® Sill Plate Barrier looks like when installed and the structure has been dried-in. While the sills are protected from beneath, there is still visible light coming into the structure from the exterior. Don’t worry! With the TERM Barrier System, that light will not be visible in the finished structure, thanks to the TERM® Base Flashing Barrier. Energy will stay in the home, and air and insects will stay out.

TERM® Sill Plate Barrier after dried-in

Check us out in two weeks for the next blog of the series, Building Out Bugs: Windows & Sheathing where we will talk about all the flashings that can keep bugs out and energy in.

The TERM® Sill Plate Barrier is a component of the pesticide-free TERM Barrier System which, when properly installed as part of the building envelope, acts as a barrier to almost all pests.  Because almost all pests are excluded for the life of the structure, the need for pesticide treatment should be permanently and drastically reduced.

To inquire about the TERM® Sill Plate Barrier for your next home or building project, or for additional information on the TERM® Barrier System products, please feel free to email me at



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