Sealing Under Capstone

gevensen · Apr 12, 2011

Were working on a church building with capstones. Inside the foyer they are getting water damage, we are in the early process of starting to repoint.
As shown by the closeup there is an old caulk between the capstones and brickwork.
Any suggestions on the best method to get a long lasting seal?

Supahflid · Apr 12, 2011

gevensen said:
Were working on a church building with capstones. Inside the foyer they are getting water damage, we are in the early process of starting to repoint.
As shown by the closeup there is an old caulk between the capstones and brickwork.
Any suggestions on the best method to get a long lasting seal?

Yes, but first, be sure and cut-out and re-seal the coping to coping joints! Do you intend to route out the existing sealant and mortar at the coping to brick connection?

gevensen · Apr 12, 2011

Supahflid said:
Yes, but first, be sure and cut-out and re-seal the coping to coping joints! Do you intend to route out the existing sealant and mortar at the coping to brick connection?

yea its all coming out, its tough stuff too, you think its good enough to remove all the sealant and repoint it ?

Supahflid · Apr 12, 2011

gevensen said:
yea its all coming out, its tough stuff too, you think its good enough to remove all the sealant and repoint it ?

You might get away with installing mortar at the coping to brick connection, but I wouldn't chance it with the coping to coping joints.

It appears as though the sealant at the coping to coping is one that contains organic solvent; very likely a urethane. We use urethanes, but silicones are a better product. And I mean commercial silicones not anything you can get at HD. And that goes for just about any sealant used for exterior commercial work IMO. Anyway, we prefer Dow Corning silicones, but there are others.

In either case, the prep and installation should be roughly the same. If you use silicone, you'll need to remove all traces of the existing sealant from the joint inner faces. The joint and joint inner faces will need to be free of all dust, debris and sealant residue. Be sure that the joint is deep enough to accept a backer rod and if not, you'll have to install something to bring up the bottom of the joint to accommodate a bond breaker tape. Hopefully there won't be any mortar in these joints and you'll have plenty of room for backer rod.

The depth of the sealant, at midpoint, should be roughly half the width; not less than one-quarter inch, not more than one-half inch in thickness regardless of width. The minimum joint width is one-quarter inch. It should be tooled with the proper tool press the sealant in to the joint and wet out the substrate to which you are bonding. Nothing to it.

Remind your customer that sealants are a maintenance item and will have to be replaced eventually!

gevensen · Apr 12, 2011

yeah it looks like a pretty big joint all the way around. I think much of there leaking is coming from there and theres one bed joint that has a 1/16 gap for about 20 ft

someone siliconed it sometime back, theres other various places where the original work was very poorly done, i hit a couple places with a screwdriver and went in 6 inches

gevensen · Apr 12, 2011

as far as the coping to brick i want to do what is going to last the longest

Supahflid · Apr 12, 2011

gevensen said:
yeah it looks like a pretty big joint all the way around. I think much of there leaking is coming from there and theres one bed joint that has a 1/16 gap for about 20 ft

someone siliconed it sometime back, theres other various places where the original work was very poorly done, i hit a couple places with a screwdriver and went in 6 inches

Without discounting broken, cracked or delaminated mortar joints in the brick, I would be very suspect of the coping to coping joints causing moisture intrusion.

The driving factor in determining mortar or sealant under the coping is whether or not that condition will receive any movement; mortar will not accommodate appreciable movement, sealant will. The greatest likelihood is that the coping won't see movement any more than the brick, thermal or otherwise. However, I would be more comfortable suggesting to the Owner that a soft joint there would be better, but the big downside is longevity. I also wouldn't be uncomfortable suggesting that a cove bead of sealant over the existing, repaired mortar would be an acceptable method to ensure the watertightness of that condition. Some others here may disagree.

If you install a cove bead of sealant, be sure to get a minimum of one-quarter inch of bond surface to the underside of the coping and the face of the brick. In doing so, you going to create a pretty large bead of sealant there which may not please the Owner. Also, to be safe, you should install a bond breaker so you don't get three-sided adhesion.

I hope I have been useful!

Edit: Oh, and I think you are saying you'll be removing the RTV silicone and mortar from joint in that last picture and re-pointing. If so, be sure to remove all of that silicone from the brick so you get a good bond with the mortar.

gevensen · Apr 12, 2011

you have been very helpful
i suspect what you do, but on close exam i also suspect the coping to brick joints are 63 years old and to my knowledge never redone. I tarred a few of those coping to coping joints in the fall and the leaking stopped in one area ( in the alley where nobody cares) but it has restarted
Its going to be a long tedious job

Supahflid said:
Without discounting broken, cracked or delaminated mortar joints in the brick, I would be very suspect of the coping to coping joints causing moisture intrusion.

The driving factor in determining mortar or sealant under the coping is whether or not that condition will receive any movement; mortar will not accommodate appreciable movement, sealant will. The greatest likelihood is that the coping won't see movement any more than the brick, thermal or otherwise. However, I would be more comfortable suggesting to the Owner that a soft joint there would be better, but the big downside is longevity. I also wouldn't be uncomfortable suggesting that a cove bead of sealant over the existing, repaired mortar would be an acceptable method to ensure the watertightness of that condition. Some others here may disagree.

If you install a cove bead of sealant, be sure to get a minimum of one-quarter inch of bond surface to the underside of the coping and the face of the brick. In doing so, you going to create a pretty large bead of sealant there which may not please the Owner. Also, to be safe, you should install a bond breaker so you don't get three-sided adhesion.

I hope I have been useful!

Edit: Oh, and I think you are saying you'll be removing the RTV silicone and mortar from joint in that last picture and re-pointing. If so, be sure to remove all of that silicone from the brick so you get a good bond with the mortar.

Tscarborough · Apr 13, 2011

A sealant joint, if done right, still does not have that long of a life. Done as crappily as that one, it has a very short life. Hire a competent Waterproofer to do a polyurethane sealant correctly, and consider sealing the head joints of the coping as well.

superseal · Apr 13, 2011

Those joints need to be throughly washed clean before you do any work, unless your planning on cleaning them up with the grinder. Regardless, you need some re-pointing of the brick (to match original) and preferably a soft joint system to the copings as mentioned.

I've had great luck with polys, but also love silicone for this application. I even broadcast sandblast sand over the joint to blend the usually wider joint.

Michael Olding · Apr 14, 2011

Hmmm... I don't know guys I think I'm in the urethane camp on this one but just a judgment call all the same.

If you use the urethane make sure to use a primer on each side of the opening to help with bonding even though urethane sticks to everything!

I have a 10 yr old shirt that still has urethane on it from a caulk job I did back then, can't keep the stuff off of me lol!

gevensen · Apr 14, 2011

You guys have been a great source thanks for allowing me to pick your brain.
I suspect those poly joints too and will grind them out after we get scaffolding set up.
Just for info I picked up those diamond die grinder bits and the are sweet for corners and hard to reach spots.
They complement the tuck point grinder real well.
They are a little slow but cut through the mortar like cold hard butter using a butter knife
Were doing the brick porch now but I notice the mortar color is whiter ( type n premixed ) but I see another thread on that.
I appreciate all the input.

Sealing Under Capstone

gevensen

Supahflid

gevensen

Supahflid

gevensen

gevensen

Supahflid

gevensen

Tscarborough

superseal

Michael Olding

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