Railjohn

IThanks for all your replies,I have tried to contact the SE,but I have had to leave a message on his answerphone,and I have E-mailed but no reply.Have noticed cracks in various places on ceilings,might be where I have been moving chipboard sheets around.Will keep eye on them for changes.Joists were put in when house was built in 1960s,some are 33 cm centres some are 43.Thanks all again.