If you do not see anything simpler, you can try grout injections in the area. It is rarely used in residential; it’s used mostly for commercial situations.

DeNeef was the standard for many years; they sold (I think), and others sprung up. You’d need to look for commercial firms if you go that route. We did and it fixed issues since (I’d bet) our house was built in the 1950s.

It’s expensive. They use the same process to seal cracks in tunnels running underneath bodies of water.

On the outside of the house at that location, there is a concrete landing about 3 inches below the bottom of the siding and there is moisture at the underside of the siding.

The finish siding or do you mean the sheathing, the layer that will be underneath the finish siding? Has the house wrap (Tyvek) been installed?

Is there a seam in the sidiing/ sheathing at the point of the intrusion?

Is this located on the weather side of the house? The side that takes the prevailing winds/ the direction from which the rain is coming?

What is probably happening is that the rain is splashing back off the concrete landing. Or running down the side of the house and infiltrating at a seam.

Thanks very much! the sheathing was Tyvek'd and hardie board and batten siding is on the house. There is a batten and the hardie panel seam about 5-6 inches to the right of the water intrusion. Hard to see, but it is the window that is closest to the garage (on the right). The water intrusion is at the spot about an inch to the right of the right side of the window.

Roof is on. We did look up and see if water was coming down, but I don't think so as it s so close to the wall and there is no water on the wall.

The cause of your water intrusion is lack of flashing.

Here is the outside. The intrusion corresponds to the right edge of the window trim. And yes, it's less than a couple inches between bottom of siding and concrete walkway.

Thank you Jim. What flashing is missing?

We had the same issue, when we had our roof replaced. The roofers did not redo the flashing along the valleys of the roof lines, when asked. We will never use them again.

Post a couple close up pics of the area at the window head and where the Hardie horizontal joints are. Water finds its own way, the leak may be 3 or more feet away. Also a couple of close ups at the landing area please.

The issue is most likely where the ROOF of the garage meets the WALL of the home. If you look, there isn't any form of eaves or flashing. That means water is running DOWN the slope of the garage-roof, hitting the edge of the house, running DOWN the wall (just to the right of the window) and into a chink in the siding...or possibly into the cement slab below the siding and then seeping UP into the space.

Water will follow gravity but it will also soak UPWARDS. Like putting a dry sponge on a puddle of water. Eventually the water is "sucked up" into the sponge and into the middle. Water moves away from it's own concentration gradient. That is to say water moves from "wet" to "dry" very nicely.

Is there a drip cap or head flashing on that window? Is there a "Z" flashing at the Hardie horizontal joints? Can you get some close ups of these areas?

I think SJ McCarthy is close. You need aluminum flashing stair stepped in the circled area. My best guess is water is traveling down the roof over the garage and it's finding its way through the seam where the garage roof meets the exterior wall (flashing blocks this) then it's traveling behind the hardie board to the edge of the window inside the wall, then down to the ground.

We had this issue, too. We had a very similar roof slope situation with a join. Hired a consulting engineering company because the GC couldn’t get it right. They specified the stair stepped flashing and I paid for an engineer to be present to ensure installation met Hardie published requirements. (You can get the PDF from their website.).

Also note that anytime Hardie terminates on concrete, you need flashing and sealing.

Don’t let them use that caulk stuff to seal you Hardie (lasts maybe 5 years). Have them use a polyurethane sealant such as Masterseal NP-1 or a paintable silicone. It’ll last three times as long.

Many thanks all!!! We will address the stair stepped flashing. Thanks very much for the sealant recommendation Milo. I will let you know how things go.

I will aree with floorfreak after looking at that picture. Sealants are no an answer for improper flashing however and will not last.