Sorry to be pedantic but my rheumatism is hurting today. Casement isn't
normally used for powder storage buildings in English (may be different
for casamata in Sp) but for reinforced artillery positions after the
Italian for 'mad house'. Storage buildings or armouries tucked a way in
quiet corners were usually only mad when they exploded on which subject
see my forthcoming paper on armies and towns in Cities in the World,
SPMA monograph series.
paul