Here is a pic of the cricket.

PPF - I see your image has step flashing. Does that make a big difference with the cricket and on the sides where brick meets the siding?

Step flashing is the traditional way -- cannot see how yours is done.

I'd be removing drywall to expose the wall cavity. A leak should be obvious.

You want to use flashing, not caulk to repair.

I'm not familiar with how vinyl siding should be installed next to a brick chimney, but I'd bet a bit of googling will locate a detail.

The cricket looks small. And there does not appear to be the correct flashing. Dunno what the detailing actually IS. It’s forensic surgery time.

"...best way to ensure no leaking around chimney??..."

1. No chimney

2. Full width cricket and step flashing (see PPF's photo)

3. Good condition for chimney concrete cap

4. Good condition for mortar in all courses

5. Move to Arizona or New Mexico.

Good luck!

Thanks for all your advice. Any thoughts on the vertical transition from brick to vertical vinyl siding on the sides of the chimney? The moisture level increases are near the corners of the fireplace and are worse with rain events with wind. Would an issue with cricket show up at the front of the fireplace or possibly in the corners? Just trying to figure out what to ask and look for.

Is your builder looking at this?

We are all waiting for water testing?

Yes - we definitely had some puddles and more fill is being brought into the yard for low spots. We have added longer drains to carry water further from the house.

I would install a larger 26 ga galvanized one piece bird's mouth with solder fillers where needed. Give it plenty of flash (12" or more) under the shingles and hold back the nails. Don't mess around with attempting to divert water with an asphalt cricket. Find an old timer with sheet metal shop, some good tin skills and solder irons & stove. If he/she doesn't have these look on.

Also consider the water entering with brick at ground and below. I do not see any exposed water proofing.

My guess is the culprit is the transition between brick and wall, particularly at the shoulder of the chimney.

Next time it rains, stand outside and watch how the rain water behaves around the chimney. If there is a chance of thunder, stay off the roof.

And it would be good idea now to complete the chimney with formed a concrete cap. The most important component in a chimney build. In addition to sealing the exposed top course of brick from weather is also locks the course in. If you proceed with this let me know and I will give you some helpful hints.

Are those concrete blocks keeping the clean-out closed? I can't see any diverters at the roof/gutter junction?

You can use a garden house on the outside of your house and chimney to try and find the leak. Start at the lowest suspected are for the leak and slowly move upwards, checking the interior after spraying one area at a time.

Virgil. I hope anyone who has water penetrating the interior of their home does not intentionally introduce more water into it. This is a very easy problem to diagnose once in the field for a skilled roofer.

Sometimes you have to force the issue. Waiting for a torrential downpour may not be the best way to correct a problem. Douching the chimney may cause some damage, but it may be less damage than waiting for a hurricane.

Aamkz. There is some poor advice posted here. Be careful.

Fixer687, that's very encouraging. Hop on over to the OP's place and give them your skilled analysis. Fact is, the issue may be roofing. But it may also be masonry. It may be the concrete wash on top of the chimney. Or the connection between the house wall framing and the chimney 'shoulders". Or something else entirely.

Glad to know experts are on the job...

Virgil. Absolutely. I have no doubt I could troubleshoot this in a half hour with a ladder and a flashlight. Garden hose not required.

Update - leak identified pretty quickly today with water test on side of chimney and shoulder. Siding/flashing on each side of chimney needs to be re-done. Flashing also has to be re-done by cricket. Thoughts on best approach for re-work of siding/flashing greatly appreciated. Have heard that it might be best to cut into the brick and attach step flashing.

Thanks for all your insight. Really appreciate it.

"Thoughts on best approach for re-work of siding/flashing greatly
appreciated. Have heard that it might be best to cut into the brick and
attach step flashing."

Best way (my opinion) to attack the chimney/asphalt shingle area is with flashing and counter flashing.

The flashing is typical step flashing. A piece of metal bent 90-degrees, one leg gets fastened to the roof deck with each course of shingles and the other leg runs vertically up the side of the chimney, floating (not secured) against the side of the chimney.

The counter flashing covers the vertical leg of the flashing that is floating against the chimney. A groove is cut in the mortar joint and an edge of the counter flashing is inserted into that joint, held in with soft metal wedges, then the gap is sealed with sealant. The counter flashing is folded down to cover the flashing.

It's a 2-piece flashing system where the two pieces move independently of one another.

Here's a reference drawing to better show what I was trying to describe.

When flashing a chimney, it's best to use a durable metal; typically copper or lead, or lead-coated copper. Something as durable as the chimney itself. If using aluminum, a thicker stock is more durable than the thinner gauges sold at most box stores.

Your cricket or saddle? Due to the geometry I prefer to not shingle them, but they can be, especially if larger in size. Small ones are typically wood framed and completely covered with metal.

Probably the most common slap-dash chimney flashing is simple single-piece step flashing that is "sealed" to the side of a chimney with several tubes of pookey. That is not the way to go.

Do you think the two step flashing would work on a stone chimney? ( I actually think our challenges are the huge spaces between the stones, but we are having issues and it has been Re flashed (single)). We have a concrete cap. Think even though our roof slope is very shallow, we need to also install a cricket. I know I’m not the OP but this thread has been very helpful.

MongoCT - Thank you for the detail on the flashing for the roof area. What about the chimney vertical stack? Should a groove be cut into the brick and counter flashed here as well?

HB. The tin shingles would be typical and the counter flashing may need to be hand formed to the stone contours. The same system as the brick flashing applies. If the chimney is below the ridge a birds mouth is always necessary.

Thank you very much!