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A homeowner preparing to install new flooring has removed the baseboards and found gaps near the slab perimeter, prompting questions about air sealing. The homeowner also wants guidance on sealing a bonus room with knee-wall attics and second-floor wall plates; the source report does not provide an answer or confirm a repair plan.
A homeowner preparing to install new flooring has asked how to air seal exposed areas after removing baseboards, reporting gaps between a slab and foundation wall and seeking advice about a bonus room and second-floor walls. The question, published by GreenBuildingAdvisor, describes possible repair approaches but does not include a confirmed diagnosis, completed work or expert response in the supplied material.
The house was built in 1993 in climate zone 4A and has slab-on-grade construction, according to the homeowner’s report. With baseboards removed ahead of new flooring, the owner says this is the only expected opportunity to access the bottom-plate area. The report says the homeowner found what appeared to be “pretty big gaps” between the slab and foundation wall on the main level.
At the slab edge, the homeowner describes concrete as thin, cracked and loose, and says it appears to sit on styrofoam. The homeowner is considering removing the loose concrete and filling the gap with Sikaflex self-leveling concrete sealant, but the report does not establish whether that product or approach is suitable for the specific conditions. No inspection findings or measurements are provided.
The other questions concern a bonus room with knee-wall attics and the bottom plates on the second floor. The homeowner says the subfloor in the bonus-room area appears continuous, with a bottom plate resting on it, and asks whether to seal from the attic or the room. They also ask whether sealing should address only the plate-to-subfloor joint or the junction between drywall and the plate as well. These are questions in the original post, not confirmed recommendations.
A Narrow Window for Sealing
Removing baseboards can expose joints that are normally hidden, giving a homeowner access before new flooring and trim are installed. The report’s practical concern is whether that opportunity should be used to address suspected air leakage at the slab edge and wall bottoms. Once the flooring and baseboards are back in place, those areas may be harder to inspect or reach.
But the source does not establish that every visible gap is an air leak, explain the role of the material beneath the slab edge, or identify the cause of the loose concrete. Those distinctions matter before material is removed or a sealant is applied. The question is relevant to readers facing similar renovations, while the missing site-specific details mean the report should not be treated as a repair specification.
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What the Homeowner Found
The report is framed as a homeowner’s request for guidance, rather than a published assessment of the house. The owner says online instructions aimed at laypeople were difficult to find and points to a Matt Risinger video as the closest example they located. They also say they had read Martin Holladay articles about the challenges of air sealing bonus rooms, while noting that their own floor assembly appears different because the subfloor seems continuous.
The supplied account does not include a response from either referenced source, a building professional’s inspection, or a follow-up describing repairs. It also does not provide photographs, drawings, the gap dimensions, or details of the slab and foundation assembly. The homeowner’s description of styrofoam and the apparent continuity of the subfloor therefore remain observations, not independently verified construction details.
“There is surprisingly little guidance online showing the specifics to the lay person.”
— The homeowner, in the GreenBuildingAdvisor question
Diagnosis and Repair Remain Open
The supplied source does not say whether the gaps are confirmed air pathways, how extensive the cracked or loose concrete is, or what lies beneath it. It also does not establish whether removing concrete could affect the slab edge or expose other issues. The proposed sealant is the homeowner’s idea, not a recommendation supported by an inspection or product assessment in the report.
For the upper floor, the exact air-barrier layout and the connections among drywall, bottom plates, subfloor and knee-wall attic are not documented. The source gives no answer on which side should be sealed or which joints should be treated. It is also unclear whether the homeowner received further advice or proceeded with the work.
Advice Before Flooring Returns
The next step described in the source is still a request for advice; it does not report a scheduled inspection, repair or follow-up. Before removing concrete or applying sealant, the homeowner would need to establish what the visible assembly is and whether the proposed product is appropriate for the actual gap and substrate. A qualified building professional can assess the slab edge and air-barrier connections in person, particularly where concrete is cracked or loose.
For any work that involves structural components or raises concerns about the slab or foundation, the homeowner should consult a qualified professional and follow applicable building requirements. The report leaves open whether the owner will address the main-level perimeter, seal the bonus-room assembly from the attic or room, or treat the second-floor plate joints before installing the new flooring.
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 at the slab edge. Those details come from the homeowner’s description and are not independently verified in the supplied report.
Does the report recommend Sikaflex sealant?
No. The homeowner said they were considering Sikaflex self-leveling concrete sealant. The supplied source does not include an expert recommendation or confirm that the product is appropriate for the conditions.
Where should the bonus-room area be air sealed?
The source does not answer whether sealing should be done from the bonus room or knee-wall attic. The homeowner describes a continuous-looking subfloor and a bottom plate on top, but there is no inspection or assembly diagram to confirm the details.
Should the second-floor bottom plates also be sealed?
The homeowner asks whether to seal the plate-to-subfloor joint and the drywall-to-plate junction. The supplied report provides no confirmed recommendation about which joints to seal or whether to do so throughout the second floor.
Source: greenbuildingadvisor.com
