What's best ? Lead sealant or Mortar

[Justin Passing]

If you have movement -surely mortar is far more likely to crack. I ( completely DIYer on this) would be up there with an angle grinder with a wire brush in it to get back to clean stone and retry flexible salant.. I'd also call the manufacturer of Lead Mate to see if there's any advice.
Dow Corning do

Dow Corning Trade Mate Lead & Gutter Seal Grey 310ml​

which is suspiciously more expensive. Sometimes you really DO get what you paid for.

 

[datarebal]

It's rare flashings are pointed properly when mortar is used .
I guess the same can be said about lead mastic . If the joint is not neat and clean then you can get issues as I previously said.
Mortar for me .

 

[Sonic70]

The lead mastic used on my dads extension was all cracked and quite easy to pull out. Doesnt sound right to mortar over the top of it either.

 

[^woody^]

Lead sealant as it is low modulus and flexible.
Mortar can crack and fall out with differential movement.

Not if done properly. It will out last the lead.

 

[^woody^]

I prefer lead sealant -which just grey silicone.

It is not just silicone. Normal silicone will sag and try to ooze out.

 

[noseall]

Not if done properly. It will out last the lead.

The one thing I have found with mortar (we use both methods) is that if you need to bend the flashings up out of the way, for whatever reason, Leadmate does behave a wee bit better.