LABC warranty is claim adverse and you would be required to pay around £1,500 towards the cost even if the claim was approved.
After four years, this would need to have been caused by a structural issue.
From your photograph it look like really poor workmanship and would have been noted had you had your home professionally snagged and inspected before you legally completed.
Rather than requesting your post be deleted, which serves to demonstrate the continuing poor quality of UK new homes, it would also be helpful to others if you would name your housebuilder!