I purchased a 3 storey Victorian mid-terrace (in clay soil) the lower ground floor of which has extensive damp. The damp surveyor recommended lowering the current lightwell patio to 15 cm below internal floor. It is currently 8cm higher than the internal floor. He recommended 15cm sub-base, 5cm gravel surface for water drainage (instead of concrete that originally the builder was to do). So, digging c. 40cm.
1. The builder said gravel over sub-base won't support the structure. We do need concrete. Is that so? If yes, how do homes have gravel surface for water drainage?
2. The trial pit revealed that the current concrete patio slab is 25cm deep. The builder believes it's that thick to support the wall, so digging it would compromise the structure. How to then safely lower the patio to address the damp issue?
1. The builder said gravel over sub-base won't support the structure. We do need concrete. Is that so? If yes, how do homes have gravel surface for water drainage?
2. The trial pit revealed that the current concrete patio slab is 25cm deep. The builder believes it's that thick to support the wall, so digging it would compromise the structure. How to then safely lower the patio to address the damp issue?
