Abstract: A method of sealing a leaking crack in a structure involves drilling a delivery channel into the structure adjacent the crack and in towards the crack to join the crack. A delivery nozzle is inserted into the delivery channel to inject a sealant comprising latex and water under pressure into the crack. The sealant may be injected until the sealant forms a seepage on an exterior surface of the crack which is sprayed with a reactive agent to cure the sealant to form a skin. Thereafter further sealant may be injected via the delivery channel after the skin is formed to enhance the ingress of sealant within the crack.