Roofing and pest control

In reply to Mary Baughman's query regarding sealing of flat roof
expansion joints, it would be useful to know if the joint(s) is in
the roof slab proper or between the roof slab and the walls.  In
either case, however, you may have to resort to bridging the joint
with a fabric-reinforced rubber material which is secured
mechanically at each edge.  Built-up roofing materials (such as used
for tar and gravel) or elastomeric membranes such as EPDM rubber
will not take the stress and flexing of an expansion joint, and foam
inserts are difficult to bond adequately and securely. Insects and
rodents will take advantage of incipient openings at joints and chew
them into reality, but they are much less likely to penetrate a
sound and continuous surface that would be presented by a tough
flexural joint covering.  Seams for such an installation must be
well-lapped and adhesive bonded, and mechanical hold-down strips
must be well caulked to eliminate creating new potential entry
points.

Joint coverings can be unsightly and look like "band-aids" if they
are visible.  Careful design is necessary for both aesthetics and
proper function.

Geoffrey Brown
Curator of Conservation
Kelsey Museum
University of Michigan
313-747-0439

                                  ***
                  Conservation DistList Instance 9:14
                   Distributed: Friday, July 28, 1995
                        Message Id: cdl-9-14-005
                                  ***