posted 01-04-2000 05:36 PM           

Since a shell keep was basically a wall it is less susceptible to weather than a tower, which requires of roof to keep the internal wooden structures from rotting. Whilst these internal structures generally just hold up the floors they do also act as braces for the stone work of the tower. Roofs were made watertight with lead and this expensive material was quickly reused elsewhere when a castle was abandoned (or it was just stolen from the castle). Shell keeps were much less likely to this sort of deterioration.

Almost all thick walls have a fill of rubble, since cut stone is so expensive. But since they are faced with expensive cut stone they are cheap quarries when they go out of use and the cut stone is often removed. Rhuddlan castle, in Wales, is a fine example of stone robbing. The walls are stripped of the facing stone to a height of about ten feet an easy working height.

Weathering is not to be underestimated, but in England's mild weather, it's effects are generally to the fine details of carvings rather than to the solid structure of walls. However, castles built with chalk, the only local rock available in parts of eastern england, are considerable more ruinous. So the quality of the stone used and, probably, of the mortar may have more effect on the survival of a castle than the type of structure.

There are several very good examples of solid shell keeps in England. Tamworth, near me, is one of the best. Totnes, Restormal and Launceston in Cornwall all survive intact (although the building within the shell are ruined or gone) Tretower and Cardiff in Wales are also noteworth. Berkeley and Fareham are variants where the motte is revetted by the stone shell wall, notably solid and unlikely to deteriorate.

Another problem with answering your question is in knowing about the unsuccessful shell keeps. Many motte exist which may have had shell keeps which collapsed and were then quarried but actual few castles have good recorded histories and many have not been excavated.

Finally a more general point about the survival of castles. Elmley Castle was built in stone in the mid 1200's and abandoned in 1315. It was used for about one tenth of the time it has existed. It is now a grassy hillock and a few stone foundations, a local bridge is reputed to be built from it's stones. It was never involved in warfare, although it was original built in earth and wood during a civil war. It is a very typical english castle, most of what we see as castles today are exceptions.

As usual my comments are about English and Welsh castles are thing may well be different elsewhere (particularly with regard to weathering)

------------------
Neurotics build castles in the air, psychotics live in them, Psychiatrists charge the rent, art therapists do the interior design and nurses clean out the garderobes!
http://www.castlesontheweb.com/members/philipdavis/index.html