They are doing what the BRE digest suggest they do, red corrosion means the lifespan on the tie is up and it will blow the mortar sooner or later. To prevent this remedial ties are suggested as a minimum action. The table they mention has 9 levels, 1 being nice clean ties, 9 being total failure.. so 6 is up the higher end.
Get a few quote to do the work, all you need in the end is a guarantee/certificate for buyer.. or let him get the quotes and reduce the selling price by that and let him get it sorted when hes moved in.
Get a few quote to do the work, all you need in the end is a guarantee/certificate for buyer.. or let him get the quotes and reduce the selling price by that and let him get it sorted when hes moved in.