Hi, i have a truss that has dropped a few mil causing the cornice to crack and bow outward. just wondering on repair methods. I have included photos from the kitchen wall inside (the wall is internal and non load bearing) and from the roof cavity. thanks
Hello @Rodlg
Welcome to the Bunnings Workshop community. It's sensational to have you join us, and thanks for sharing your question about your roof truss.
From the photos, it does appear that the cornice crack lines up with the wall beneath a roof truss, which suggests the truss may have settled or moved a few millimetres. Even a small amount of movement can be enough to cause the cornice to bow slightly and crack, particularly where an internal non-load-bearing wall meets the ceiling. The truss connector plate in the roof also doesn't immediately stand out as having failed, so the movement may be due to the truss itself, the supporting structure, or normal settlement, but it's difficult to determine the exact cause from photos alone.
Before carrying out any cosmetic repairs, I'd recommend engaging a qualified builder to investigate why the truss has dropped and to confirm whether the movement has stabilised. While it may turn out to be a relatively minor issue, it's important to identify the cause first rather than simply repairing the crack, as the movement could continue and the cornice may crack again.
Once the builder has assessed the roof framing and is satisfied that everything is structurally sound and no further movement is expected, the cornice can usually be repaired by carefully removing any loose material, re-adhering or resetting the bowed section if required, filling the crack with a suitable cornice cement or patching compound, sanding smooth and repainting. If the cornice has pulled away significantly or become damaged, replacing that section may provide the best finish.
I think you're taking the right approach by checking the roof cavity before repairing the plaster. Having a builder assess the truss first will give you confidence that you're addressing the underlying cause, not just the visible crack, and will help ensure the repair lasts.
Here are some handy step-by-step guides - How to repair cracks in plaster and How to patch plaster.
Please remember to wear personal protection such as gloves, goggles and a mask.
If you need further assistance, please let us know.
Eric
Hi @Rodlg
How old is the house? some builders give quite long warranties on new house construction so it may be worth getting the original builder back if that is possible.
