How to seal siding to keep out mice.
How to seal vinyl siding to concrete.
Don t use a synthetic bristle brush the acid dissolves the bristles.
You may need to tape the rubber to the siding temporarily until the caulk dries.
Test the acid solution before using it.
Theoretically you could seal the tar paper to the foundation with foam spray caulking something similar.
Seal the hole from the inside as well.
Not a vapor barrier as you say but it prevents water that makes it past the siding from getting any further into the wall.
If it s safe spread it liberally in the concrete with a natural bristle paint brush.
A wall or siding needs special detailing to prevent leaks and damage where the wall encounters any horizontal surface such as a foundation wall top or a concrete porch slab.
Maintaining good clearances between finish grade and siding materials of all kinds is crucial to preventing this kind of damage.
Crawl around the exterior of your home and use a flashlight to find cracks holes and gaps.
It s safe for vinyl but your siding may not be 100 percent vinyl.
Look under the siding at the area meeting the foundation of your home for holes and gaps.
Use the cut off piece to start the next row of siding.
Add vinyl siding strips until you reach the end of the wall then measure and cut the last strip to leave 1 4 inch space at the end.
The grey color visible in the picture is the back side of the vinyl siding.
Use minimal expanding foam to avoid opening the slit in the rubber boot and push the tip several inches in so the foam expands into the hole instead of out the top of the boot photo 4.
This article series provides details of foundation tops building walls exterior trim wall corners and roof wall intersection flashing to prevent leaks water damage.
Let the caulk dry overnight then partially fill the boot with foam.
I believe you have tar paper under your siding based on your description.