Tenting on historic tiled floors

We have had a run of enquiries lately on Edwardian and Victorian
tiled floors where a 'tenting' phenomenon has occurred.  Entire
sections of flooring are damaged when delamination occurs between
the tile and adhesive, and the substrate.  This appears first as a
hollow sound to the floor (although we are not convinced it can be
predicted) and then catastrophic failure occurs where a line of
tiles lift in the middle, creating a 'tent'--similar to the
formation of mountains by pressure from either side.  Witnesses to
these events have said there is a sound like hailstones as the tiles
lift.

We have not found any reference to this phenomenon in literature
about historic tiles, which most often focuses on surface decay,
however modern tilers attribute this to changes and drying out of
the substrate, or thermal differentials between the ceramic tiles
and the substrate, and advise the cutting in of expansion joints. We
have noticed that the joints do tend to be very fine in the floors
where this occurs, and the growth of salts does not appear to be a
trigger.

Where we have been asked to repair floors that are suffering from
this, it is likely that the issue is ongoing and historic as past
repairs can be seen.  We are very keen to find a long-term solution
to this problem, and would welcome suggestions or experiences of
other DistList members on this.

Berenice Humphreys
Cliveden Conservation
Home Farm
Ammerdown Estate
Kilmersdon
Bath BA3 5SN
+44 1761 420300
+44 7876 561341


                                  ***
                  Conservation DistList Instance 28:19
                Distributed: Saturday, October 11, 2014
                       Message Id: cdl-28-19-020
                                  ***