This blog is part of a series about air barrier transitions to help continuity. Check out Air Barrier Transitions Simplified: Applied Rafter Tails, and Air Barrier Transitions Simplified: Floor Transitions

The home’s air barrier should be complete and continuous. There will be air barrier transitions between different airtight materials. A home’s concrete foundation often has two air barriers: the poured concrete is airtight (grout connections in masonry block walls aren’t airtight) and the subslab vapor barrier (with seams airsealed with a tape) is airtight.

The subslab vapor barrier acts as a capillary break between the concrete and the soil. It’s important to ensure that concrete foundations have sufficient capillary breaks and that there’s capillary breaks between wood framing and the concrete. 475 offers EXTOSEAL FINOC as a capillary break tape for beneath wood mudsills and 475 offers a STEGOHOME system for subslab vapor barriers.

You can see the red STEGO Tape used to tape the STEGOHOME seams. 475 also offers COMPEGO tape as an option

COMPEGO tape airsealing STEGOHOME membrane seams

Mineral wool board insulation installed over the STEGOHOME membrane

It’s best practice to run the subslab vapor barrier long around the perimeter of the install so that it can be taped to the wall’s air barrier.

The subslab vapor barrier runs up the wall at the perimeter to be taped to the INTELLO Plus membrane

The subslab vapor barrier is available to be taped to after the concrete was poured

COMPEGO tape used to tape the subslab vapor barrier seams and it’s running up the concrete wall for the air barrier transition

You can see the red STEGO Tape used to tape the subslab vapor barrier seams. The membrane is running long to the exterior to be taped to the exterior wall’s air barrier

The wall’s bottom plate was placed over the subslab vapor barrier so the vapor barrier can be taped to the wall’s exterior air barrier

Plywood sheathing seams taped with TESCON VANA tape and you can see the “floppy bit” of subslab vapor barrier that will be taped to where the framing meets the concrete

The EXTOSEAL FINOC tape is used below the wall’s bottom plate (mudsill) as a capillary break, but it can also be installed wider than the wood plate so that you can tape the wall’s exterior air barrier to this tape – transiting the air barrier from the exterior to the interior. The wall’s exterior air barrier and WRB then typically runs long past this to transition to be taped to the below grade vapor closed waterproofing. 475 does not currently offer solutions for this exterior below grade wall waterproofing system.

ADHERO is taped to the exterior side of the concrete wall which is then waterproofed with a vapor barrier multi-coat rubberized foundation sealer with gravel that creates drainage to the french drain at the concrete footer

CONTEGA SOLIDO IQ can adhere to masonry without the need for a primer and the wall’s WRB can tape to this tape at the exterior wall to foundation transition. CONTEGA SOLIDO IQ-D can be used to adhere to the backside of the SOLITEX MENTO 1000 membrane.

VIDEO shows using the CONTEGA SOLIDO IQ-D tape for the SOLITEX MENTO 1000 to foundation transition

If the project is using a pier foundation or has an unconditioned basement then the foundation’s air barrier is typically a SOLITEX MENTO membrane running on the underside of the floor system (See “WRB Cheat Sheet” post for selecting the proper exterior membrane). If the space below the floor system is unvented or has consistently high humidity levels then it’s best to use the lower vapor perm membrane CONSTIVAP PLUS on the underside of the floor system.

Here you can see the ADHERO 3000 WRB on the wall running long that’ll get taped to SOLITEX MENTO 1000 that’ll be on the underside of the floor system - notice the “floppy bits” of SOLITEX MENTO 1000 placed between the framing supports and the floor system to be later connected to SOLITEX MENTO 1000 running on the underside of the insulated floor system.

Pier foundation with SOLITEX MENTO “floppy bits” installed to ease the connections for a continuous air barrier below the floor system

Pier foundation with SOLITEX MENTO “floppy bits” installed to ease the connections for a continuous air barrier below the floor system

Unconditioned cellar detail from 475 Smart Enclosure ebooks

Unconditioned cellar detail from 475 Smart Enclosure ebooks

These best practices are integrated into a variety of construction types in 475’s Smart Enclosure Details. Download them for free to simply drag and drop details into your plans.