Seal between parapet gaps

I have a metal parapet running around my rooftop terrace. Where one piece of the metal parapet joins another, there is a filling of some kind to seal the gap. This sealant has cracked. Do I have to completely clean out the old sealant or can I fill the cracks?
What product do I use to replace or repair the sealant?

[quote=“itredler”]I have a metal parapet running around my rooftop terrace. Where one piece of the metal parapet joins another, there is a filling of some kind to seal the gap. This sealant has cracked. Do I have to completely clean out the old sealant or can I fill the cracks?
What product do I use to replace or repair the sealant?[/quote]

Yes, you SHOULD clean out (rake out) the old sealant first; otherwise you would be applying new sealant on top of failed sealant.

Next, the type of sealant depends on what is presently in place. If it is a silicone, then you are pretty much confined to re-using silicone. If not, then I would suggest something along the lines of NP-1 polyurethane sealant. Depending on the size of the joint, you may also need to install backer-rod. I’d recommend closed-cell backer-rod, but make sure you don’t puncture it while stuffing into the joint. Also, your sealant joint depth should be 1/2 the width.

Thanks for the very complete and helpful reply.
How can I tell if the current filler is silicone or not?

Based on you stating that the current sealant is cracked, I would say it isn’t silicone. Silicone will remain flexible and not dry and crack.

Cerberus has great info on the repair. Polyurethane is the way to go.

You might also consider a polyether. Product such as Chem Link M-1. Advantages of urethane and silicone.