Massive concrete crown

[Ross Neag]

Haven't seen one this size before and certainly unsure if solid concrete or formed with interior void. It got my and the to-be homeowner's attention. Single family, two years old. Wish the cricket was elevated a few courses but...

Am I over-reacting or does this appear normal? No slip joint between clay flue and crown and two (one per flue) small hairline cracks running from flue/crown penetration down center of crown at EACH flue.

[Gunnar Alquist]

Haven't seen one this size before and certainly unsure if solid concrete or formed with interior void. It got my and the to-be homeowner's attention. Single family, two years old. Wish the cricket was elevated a few courses but...

Am I over-reacting or does this appear normal? No slip joint between clay flue and crown and two (one per flue) small hairline cracks running from flue/crown penetration down center of crown at EACH flue.

Sorry Ross, never seen one that massive either. But then again, I rarely see much more than a crown wash.

I doubt the cracks are significant at this point, but the lack of a gap between the flue tile and crown will probably cause the flue pipe to crack when it heats up. I certainly would note it and make recommendations.

I can't remember if I got this diagram from this site or from the Brick Institute of America. The gap at the flue tile/crown connection should be caulked, but the diagram does not have the instructions.

[Michael Thomas]

Gunnar,

It's from Jack Pixley's site, look for the "Tops To last a Lifetime" link mid-way down the left-hand side.

Here's a version I created for use in reports:

-------------

Ross,

"Wish the cricket was elevated a few courses but..."

Judging by the picture, that's not a cricket, just a flashing.

With a flat top and no flue-cap separation, IMO that's indeed headed for problems in our Chicago Climate.

[Ross Neag]

GA and MT,

Thanks, I hit all the significant hot buttons on this. Client is roofing contractor and was on same page and fully understood details. He didn't like it and was going to remove it and replace with less 'stressful' crown.

MT, there was a cricket w/o let-in flasing, but just really shallow. If it were elevated--can't see in pic--by 3 or four course it would have been better.

[Michael Thomas]

Yup... I see it now (the cricket, that is)

[Bob Knauff]

In a snowy/damp, cold climate such as Chicago even hair line cracks in a masonry crown can be devastating over time. As snow or ice melts even in the dead of winter due to the suns heat or warmth from a fire below, the water can run into even the tiniest cracks and will re-freeze causing splitting or spalling and the inevitable downward spiral of damage, if left unattended. I recommend at least caulking even the tiniest cracks in a concrete crown but since they normally have more problems along with that anyway, it's common to recommend replacement with one like that shown in the Pixley image. I even include the drawing in the report and try to impress upon the client the importance of the contractor making one exactly like it.

Cricket or Saddle Height:

R1001.17 Chimney crickets. Chimneys shall be provided
with crickets when the dimension parallel to the ridgeline is
greater than 30 inches (762 mm) and does not intersect the
ridgeline. The intersection of the cricket and the chimney shall
be flashed and counter flashed in the same manner as normal
roof-chimney intersections. Crickets shall be constructed in
compliance with Figure R1001.17 and Table R1001.17.

Roof Slope ------- Height

12 - 12 --------- 1/2 of W
8 - 12 ---------- 1/3 of W
6 - 12 ---------- 1/4 of W
4 - 12 ---------- 1/6 of W
3 - 12 ---------- 1/8 of W

[Eric Barker]

These crowns are common in my area and they crack too. As for an isolation joint between the liner and the crown - well we pretty much seldom see that detail. Bob is absolutely on the mark about the hairline cracks. There a point for water entry - maybe not a lot but they're enough to cause some long term freeze/thaw troubles. I don't recommend that the cracked crowns be replaced - they'll only be install again without the proper joint then crack again. Rather, just seal the crack and be done with it.

[Ross Neag]

Thanks all. It was a learning lesson with him on the roof, at least for me, as he was a family trained and professional roofing contractor and very kind about sharing information without sounding like a know it all. I wish I had more clients like that.

Happy 4th...