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Shingles on a small roof saddle behind a chimney.

Chimney Leak Prevention:

Building A Chimney Saddle
To Divert Rain Properly
Part 2 - Shingles

A Chimney Needs A Saddle Or "Cricket" To Control Water Flow

 
In This Article:

Tar paper is laid over the sheathing and shingles are nailed to each side of the saddle, then the ridge, then woven into the shingles on the existing roof.

Related Articles:
Skill Level:
3 (Intermediate)
Time Taken:
About 3 Hours
Author:
Project Date:
December 1999
 
 
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After I built the wood framing for the roof saddle, I needed to apply some basic 3-tab roof shingles and weave them into the existing shingles on the main roof. While I saved the old shingles I removed before building the saddle, I needed to buy more shingles, and I couldn't find an exact color match.

The homeowner had a partial bundle of 3-tab shingles whose color was close to the original roof, and I used the salvaged original shingles for some patching on the front side of the roof, where an exact color match was important.

 

See Part 1 - Framing the roof saddle.

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First, Some Flashing Issues:

Old metal flashing where roof meets chimney.

First, I removed the shingles beside the chimney. With all that tar, it was a big mess.

Notice how the aluminum flashing extends down from the chimney and then curves outward. This is really strange.

Flashing that is embedded in masonry, and extends above the roof, is called "counterflashing". Counterflashing is supposed to be used to cover the edges of regular flashing that goes under the shingles and against the chimney.

 

 

 

 

Also, I covered the newly-built saddle with a piece of roofing felt (tar paper).

Tar paper covering new section of roof, behind chimney.
 

 

Replacing roof shingles and step flashing at chimney.

I pruned back the aluminum flashing with a pair of tin snips.

I also installed a piece of "starter strip" shingle next to the chimney... but I installed it upside down (the tar strip is supposed to be at the lower edge). That's not a problem, though, because later I can just apply some roofing tar on the top and bottom of the lower end of this shingle, and everything will stick to the roof.

 

 

Next I installed a piece of step flashing over the starter shingle.

Then I installed a full depth shingle directly on top of the starter shingle, and another piece of step flashing (red arrow).

New step flashing where roof shingles meet masonry chimney.
 

 

Close-up photo of step flashing and counter-flashing on masonry chimney.

Another view of the first two pieces of step flashing.

The red arrow points to the last step flashing installed. The blue arrows point to the counterflashing. 

It is very difficult for water flowing down the roof to get behind this flashing, even though the counterflashing is quite bent. Some carefully-applied roof tar (or silicone) behind the counterflashing will keep it stuck to the chimney.

 

 

The third row of shingles took me to the back edge of the chimney. The step flashing had to be cut short to fit under the old chimney counter-flashing.

As you can see by the black mess, I had already applied some tar behind the counter-flashing.

New asphalt shingles and flashing against a chimney.
 

 

Step flashing bent around corner of chimney.

I cut a piece of flashing that went around the corner. I used a concrete block to hold the flashing to the chimney, after squirting some tar behind it.

Several years after doing this project, I discovered bendable step flashing, which can be bent around a corner to maintain a seam-free flashing in a situation like this. Bendable step flashing has corrugations which allow the metal to stretch.

 

 

Shingles In The Valley:

 

This will be a "woven" valley, meaning that the shingles from different planes will overlap each other.

I tried to keep the nails as far from the valley as possible. I didn't like having the "break" between shingles this close to the valley, so I applied plenty of tar to any break points, once the next row of shingles was installed.

Asphalt roof shingle in valley between different roof surfaces.
 

 

Roof shingles on a roof saddle behind a chimney.

I installed another shingle on the main roof, and then I did the first shingle on the saddle.

To do a proper woven valley, the shingles should reach far beyond the center of the valley... we had a limited number of shingles, so I used an off-cut shingle here. A longer shingle would have been better. 

 

 

The next shingle, from the main roof, over laps the previous shingle. Also, a step flashing (red arrow) was installed next to the chimney.

Roof shingles being applied to a small saddle behind a chimney.
 

 

Asphalt roof shingles at the peak of a small saddle or cricket.

Another shingle added to the saddle. Note how the top part of the shingle is folded over the peak.

 

 

Another shingle added to the main roof. This pattern of overlapping in the valley is called a "woven" valley.

Roof shingles in a woven valley.
 

 

A Potential Problem When Doing A Woven Valley:

It's easy to install shingles across the valley and not have the shingle pushed down fully into the valley. Then the shingle "spans the valley", or acts like a bridge across the valley. When this happens, there is air behind the shingle, not roof plywood, and when somebody steps on the shingle, the shingle gets ripped. And then the valley leaks. Note that the valley is like a funnel.

Many years ago, when I owned my first house, I got up on the roof to inspect something. I stepped in the valley and tore right through the roll roofing material. (It was an "open valley" with roll roofing in the middle.) But the roof never leaked... perhaps because there were 3 layers of shingles, and all I did was create a leak between layers. In other words, I got lucky.

Make sure the shingles are pressed firmly into the valley before nailing.

Apply roofing tar under the shingles to help hold them in place. 

 

Step flashing at peak of roof against chimney.

The top piece of step flashing had to be split in order to fit.

Flexible step flashing would work well here. 

 

 

No more shingles were needed on this side of the saddle at this point.

(The peak will be covered with single-tab ridge shingles.)

The next shingle for the main roof was laid out to see how it would fit

Roofing on a saddle for a chimney.
 

 

After this, I spent some time shingling the other side of the saddle. The sun went down during that time, so the remaining photos were taken at night.

 

New roof shingles on a chimney saddle used to divert rainwater around a chimney.

The top shingle on the second side of the saddle is visible. It just covers the ridge.

 

 

The next step was to place the first full shingle that crosses over the ridge.

This was just for layout purposes... I didn't actually use a full shingle here. 

Laying out roof shingles over a gable or saddle where it joins the main roof.
 

 

Cutting roof shingle so it can lay flat on multiple roof surfaces.

This "cross-over" shingle (which is just 2 tabs of a 3-tab shingle) had to be split, or it would not lay flat. A slit was cut part way through, from the top.  This slit runs in line with the valley center-line.

 

 

The next shingle in the row was cut to length.

Cutting shingle to length with tin snips.
 

 

Applying roof tar to split in roof shingle.

I filled the slit with roofing tar. I usually use a lot of roofing tar to fill any gaps around the valley areas.

I can't tell how well insulated and ventilated this house is, so there could be a problem with ice dams in the winter. When ice forms near the edge of the roof, melting snow can find it's way under shingles, because it can't escape downhill.

 

 

I have seen enormous problems with ice dams forming around chimneys, because some chimneys give off a lot of heat, especially masonry chimneys with fireplaces or less-than-high-efficiency furnaces.

Note: No further shingles can be installed until the ridge is capped.

 

 
 
 
 
 
 
 
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Ridge Cap Shingles:

The ridge was capped with single tab shingles, cut from three-tab shingles. (I used tin snips.) The cap shingles were installed from the chimney towards the main roof.

Roof saddle with ridge cap shingles.
 

 

Another view of the ridge cap shingles.

 

 

Last Ridge Cap Shingle:

The last cap shingle had to be split, so it would lay against the old roof.

Note how the black tar strips almost line up with the other shingles. (That's a lucky coincidence.) The next row of shingles will cover this junction nicely.

Ridge cap shingles meet the main roof.
 

 

From this point on, the task is a straightforward matter of installing shingles to fill in the area where they were removed at the beginning of this project.

 

Chimney saddle after shingles are completed.

The next day I took some better pictures. The shingles will lay more flatly to the roof after they go through a warm summer.

 

 

Completing The Flashing: 

First I applied a bead of roofing tar way down deep behind the flashing, being careful not to bend the metal too much.

Then I used silicone caulking to seal the top of the step flashing against the chimney. I would have used clear silicone, but I had run out, so I used what I had, which was black. The color didn't matter here because this area can only be seen while standing on the roof.

Applying silicone caulk to top edge of step flashing where roof meets chimney.
 

 

Note that to do a proper roofing job, this flashing should be covered by a counterflashing, as seen earlier. The homeowner didn't want to spend any extra money at the time, so we left the step flashing with the top edge uncovered. While not advisable, this approach often works just fine. I have seen dozens of chimney and wall flashings with no counterflashing, and they never had leak problems.

Click here to view an article that shows how I fixed up the flashing on the sides of the chimney.

 

More Info:
Tools Used:
  • Basic Carpentry Tools
  • Pry Bars
  • Tin Snips
  • Caulk Gun
Materials Used:
  • Roofing Felt (Tar Paper)
  • Shingles, 3-Tab
  • Roofing Nails, 1¼"
  • Roofing Tar
  • Silicone
 
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