b'TECHNICAL & RESEARCH Continued from page 7Figure 4. Raised corners edges of saturated polyisocyanurate board.Figure 5. Raised edges of cover board.manufacturers require that insulation boardsbeingplacedontop be placed in the wet adhesive before the adhe- while the foam adhe-sive skins over or starts to dry. Some manu- siveiscuring.This facturers recommend that the worker placingcan be evidenced by the insulation or cover board into the adhesivetheinstalledboard walkintheboards(walkacrosstheboardhavingraisededges afterplacingitintheadhesive),andsomeandcorners,uneven manufacturersrecommendthattheworkersboards, lack of solid adhesion, or loose boardsadhered to the substrate below (see Fig. 4 and 5).roll the board in the adhesive with a weightedwhen boards are installed across transitions inTheseconditionscanbefurthercompli-landscape roller. slope, crickets, or saddles. Any raised edges orcatedwithotherinstallationerrorssuchas However, I have learned from personal expe- corners of the boards could telegraph throughinstallingfastenersandplatestoholddown rience that there can be undesirable results whenthe finished roof surface or result in unadheredraisededgesandcorners.Forexample,the these manufacturer-prescribed methods are fol- areas of insulation or cover boardor both ofthermoplastic olefin (TPO) membrane system lowed.Whenboardsarewalkedinorrolledthese problems could occur. You may feel looseshown in Fig. 6 was meant to be an adhered withalandscapingroller,thefoamadhesiveboards while walking across the roof. TheseTPO membrane over adhered coverboard and may not be held in solid contact with both theboardswilltypicallymovedownwardwhenadhered polyiso. The contractors repair with substratesurfaceandtheundersideofboardyou step on them, indicating that they are notfasteners and seam plates introduced thermal bridging into this assembly, and the fasteners penetratedthevaporbarrier.Inmyperson-alexperience,iftheinstalledfastenersand platesareinstalledatthejointbetweentwo boards using 2-in. (50-mm) seam plates and covered with TPO membrane patches, there is also a considerable risk that the fasteners and plates may not hold down the loose or cupped boards over the long term. The introduction of insulation plates and fasteners also means this assembly does not qualify for the specified hail coverageunderthewarranty.Addingmetal insulation plates introduces a very hard surface directlybelowtheroofmembrane.Theroof manufacturers hail warranty terms and con-ditions are very specific in requiring the roof substrate to be adhered and not mechanically attached. These conditions also place the roof Figure 6. Seam plates installed and spanning across two boards in an attempt to hold downsystem at risk to high-wind damage. The par-raised edges of cover board, bowed or cupped boards, and loose board edges. ticular system depicted in Fig. 6 was specified 8 www.mrca.orgMidwest Roofer37'