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A homeowner preparing to install new flooring asked GreenBuildingAdvisor readers how to air seal exposed baseboard areas in a 1993 slab-on-grade house. The report describes cracked concrete and questions about a bonus-room knee wall, but it does not include expert answers or a confirmed repair plan.
A homeowner preparing to install new flooring has asked for guidance on air sealing exposed areas in a 1993 slab-on-grade house, after finding cracked, loose concrete and gaps near the slab perimeter. The GreenBuildingAdvisor question also raises uncertainty about sealing a bonus room’s knee-wall attic and second-floor wall plates; the supplied report does not include answers or confirm that any work was done.
The homeowner said the house is in climate zone 4A and that all baseboards had been removed before new flooring was installed. The removal gave access to the bottom-plate area, which the homeowner saw as a limited opportunity to check for places where air could pass through the building envelope.
On the main level, the homeowner reported gaps between the slab and foundation wall. At the slab edge, some concrete appeared thin, cracked and loose, and seemed to sit over material the homeowner identified as styrofoam. The homeowner proposed removing loose concrete and using Sikaflex self-leveling concrete sealant, but the source does not establish whether that product or approach is suitable for the specific condition.
For an upstairs bonus room with knee-wall attics, the homeowner asked whether sealing should be done from the attic or the room side. The reported floor assembly appeared to have a continuous subfloor beneath the bottom plate. The homeowner also asked whether sealing should address only the plate-to-subfloor joint, or the drywall-to-plate junction as well, including along the second floor. These are questions posed in the report, not recommendations from a building professional.
Air-Sealing Access Before New Flooring
With the baseboards removed, the homeowner has access to joints that may be harder to reach after the flooring and trim work is complete. That makes the timing relevant: the reported gaps can be inspected before the project moves forward, while the condition of the concrete edge and nearby materials can also be assessed.
But the report does not establish that every visible gap is an air leak, or that sealing a single joint will improve comfort or energy performance. The slab-edge damage described could require an evaluation beyond choosing a sealant. A repair should account for the actual materials, movement, moisture exposure and condition of the concrete. The same care applies upstairs, where the correct air barrier depends on how the floor, wall and attic assemblies connect.
For readers undertaking similar work, the practical takeaway is to distinguish a question about air leakage from a diagnosis of a building defect. Where concrete is loose or cracked, or where the assembly is unclear, a qualified building-envelope or concrete professional can inspect the area before material is removed or applied. The supplied source offers no verified repair instructions.
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What the Homeowner Found
The question was published by GreenBuildingAdvisor, a building-science publication, and describes a homeowner seeking detailed guidance rather than reporting a completed project. The house was built in 1993, uses slab-on-grade construction and is identified as being in zone 4A. The homeowner said online instructions aimed at laypeople had been difficult to find.
The homeowner referenced a video by Matt Risinger and articles by Martin Holladay about challenges in air sealing bonus rooms. Those references indicate what the homeowner had consulted; they do not, in the supplied material, resolve the conditions in this particular house. The homeowner specifically suggested that the continuous subfloor and bottom-plate arrangement might differ from examples discussed in the articles.
The source frames three questions: how to handle the slab-to-foundation gaps and loose concrete, where to seal around the knee-wall attic, and whether to seal bottom plates throughout the second floor. It provides no measurements, photos, inspection results or reply from a contractor or building-science expert.
“I was hoping to air seal wherever necessary.”
— The homeowner, in the GreenBuildingAdvisor question
Condition and Repair Method Unconfirmed
The supplied report does not say whether the slab-edge material is in fact styrofoam, how wide or deep the gaps are, or whether the cracked concrete is structurally significant. It also contains no assessment of moisture, movement, or the construction details needed to select a compatible sealant. The homeowner’s proposed use of Sikaflex is a question, not a confirmed recommendation.
There is also no answer on whether the bonus-room air barrier should be accessed from the attic or the room, which joints should be sealed, or whether the second-floor plates need treatment. No professional inspection, completed repair, permit requirement or energy test is reported. Those details remain unresolved.
Inspection Before Sealing or Flooring
The next step described by the source is not a confirmed project milestone: it records the homeowner asking for advice. Before removing concrete or applying sealant, the homeowner should identify the materials and have the damaged slab edge assessed if its stability or function is uncertain. For work involving structural elements or significant concrete repair, use an appropriately qualified professional and follow applicable building-code and product instructions.
For the upstairs area, the assembly should be examined to determine where the air-control layer is continuous and accessible before choosing a sealing location. The report gives no schedule for a response, flooring installation, inspection or follow-up, so whether the homeowner receives guidance or proceeds with repairs is unknown.
Key Questions
What did the homeowner find after removing the baseboards?
The homeowner reported gaps between the slab and foundation wall, along with thin, cracked and loose concrete near the slab edge. The homeowner thought the concrete rested on styrofoam, but the material is not independently confirmed in the report.
Does the report recommend Sikaflex for the slab gaps?
No. The homeowner suggested using Sikaflex self-leveling concrete sealant as a possible approach, but the supplied report contains no expert confirmation that it is appropriate for the specific gap or damaged concrete.
Where should the bonus-room knee-wall area be air sealed?
The report asks whether sealing should be done from the attic or bonus room, and whether the plate-to-subfloor and drywall-to-plate joints should be addressed. It does not provide an answer; the assembly details need to be assessed before selecting a location.
Is there a confirmed repair outcome?
No. The source records a homeowner’s questions and observations, but does not report an inspection, a professional recommendation, completed work or a result.
Source: greenbuildingadvisor.com
