Cracking walls over basement

kakashka

Hello,i have a basement constructed with reinforced conc wall 325mm thick on top of reinforced slab of 400mm thick,all steel is A393 sheet with 2layers all round and under and top of wall also has 6 x20mm rebar all round,dimentions are 17m X 10 m divided into 3 sections,1 section wall has a 5 m ope with 2 rsj heads 18''and16'' on top of each other running full length of wall front to back(10m)on top of this i have 200mm floor slabs with rising walls constructed fron dense conc block,outer leaf started on basement wall,inner on slab on basement wall,80mm insul,end and 2 division walls are block on flat,all 3m high with 200mm slab for 1st floor also(2story over basement)2nd floor wall is dense conc outer with Quinn lite inner(which have been a nightmare to use!!)which is at present approx 6 courses high..the problem..CRACKS,all opes have cracks running vertically outside,wider at top,disappear at DPC, and 3 have horizontal cracks inside,there are NO cracks in basement,not even a hair line,engineer's have no explaination for it,can anyone shed some light,WORRIED

sinnerboy

is the building 17m long ?

you need expansion joints in blockwork

-every 6m
- at every major opening ( 5m is pretty major )
- at locations where hieght of wall changes - i.e. if builing changes from single storey to two storey

if no expansion joints - this could be your problem

kakashka

yes building is 17m long,straight wall and wil be approx 6.5m high when finished,no expansion joints and none specified either but you may be right as it all seemed to happen suddenly(last weekend!!)but end wall also cracking at opes(2windows)
end walls are 10m long and will be approx 9.5m to ridge
would 10m wall also need expansion joint?surely lots of houses this size with no expansion joints?
Thanks for help

sinnerboy

blockwalls expand and contract

over 6m - forces cause cracks

weak spots are openings- cracking concentrates here

suggest you purchase homebond manual

Pataman

Contact the structural engineer you used.