Ok, not siding, let me explain: I just pulled brick veneer off of part of the front of my house to replace it with siding. This house was moved here in the late '70s. There is a 6'x8' poured concrete porch about 1 1/2' tall, it doesn't appear to be attached to the house because there is a 1/4 to 1/2" gap where it meets the house. I just discovered that the sill is behind this porch.

I can't get the new siding down into the space between the porch and the house to cover the wood. How in the world can I keep water from working its way down between the porch and the house and rotting the sill?

 

When I come across a situation like that, I will usually make a galvanized wall flashing (L-flashing), generously caulk the cement, then push the flashing down into the caulking. If the caulking is far enough behind the front of the flashing so that it doesn't "squeeze out" as you push the flashing down, that usually looks best. Nail the flashing to the wall, apply your WRB (house wrap), seal it to the flashing with flashing tape, then surround the concrete with a trim board that's a minimum of 2" wide.

Apply a z-flashing over the top piece of trim (but not the sides). Your siding can butt up against this trim on the sides (and get caulked to the trim) but keep the top piece 1/4" above the flashing, and do not caulk the 1/4" gap. I have recently started to make a 1/4" tall upward bend on my (drip cap) z-flashings to act as an end dam, so that water isn't as likely to run off the ends. It also gives you the proper spacing when you set the siding on top of the upward bend, provided that upward bend is 1/4" tall. I caulk both sides of both end dams where they meet the wall.

 

WHEW! Thank you for that info. I about had a heart attack when I saw that, thinking that the porch had to come out. I want to move the front door eventually but not right now and not under circumstances like that.