CASE STUDY:
BLISTERING IN LINOLEUM FLOORING INSTALLED OVER A CONCRETE SLAB-ON-GRADE By Stephen Hunter, P.Tech. (Eng.), FSFE Introduction This case study is about a failure involving blistering in linoleum sheet flooring installed over a concrete slabon-grade in a school constructed on the Canadian prairies. (Photograph 1). It includes a summary of the investigation methodology and observations. There is also a discussion on why the failure occurred and what could have been done to prevent it.
Methodology This investigation started with a conversation to understand the issues. We then reviewed the design and construction documents. This was followed by a visit to the school to review the issues first-hand. During our site visit, the moisture content of the floor assembly was recorded in several locations – both
where the blistering was occurring and where it was not. At some blister locations, the linoleum flooring was cut and removed to examine it and the underlying assembly. To better understand the composition of the concrete slab-on-grade floor assembly as a whole, core samples were taken at several locations.
Observations The floor assembly was illustrated in the drawings as follows (from top to bottom): • Linoleum sheet flooring • 100 millimetre concrete slab • 6 mil polyethylene sheet layer • 150 millimetre granular fill The floor was slightly above grade and Figure 1: Approximate building footprint with the service ducts indicated by dashed lines. The locations of blistering are indicated by red circles.
was bordered on the building perimeter by concrete foundation walls with strip footings. The foundation walls extended approximately 1.5 metres below grade. The foundation wall assembly was illustrated in the drawings as follows (from exterior to interior): • 1 3 millimetre concrete facing above grade • 5 0 millimetre extruded polystyrene insulation panels • 200 millimetre concrete No membrane was shown in the drawings between the foundation walls and either the above grade walls or slabon-grade. No drainage tile was shown in the drawings. During our document review we also learned that two concrete service ducts were present on the site prior to construction. Both service ducts extended through the building footprint. One duct ran north/south and the other ran east/west (Figure 1). The service ducts measured approximately two metres wide by one metre high. During construction, the concrete service ducts were abandoned and filled with soil. They were not blocked or sealedoff where they entered the building footprint.
Photograph 1: Typical blistering in the linoleum sheet flooring. 22
AN ABECN/ABECS PUBLICATION
At each duct location, the full height foundation wall was interrupted and a 0.6 metre high grade beam was
