When we pull an old stoop off the front of a Long Island house, we often find the same thing. The bottom course of siding was run down behind the stoop or sitting right on top of it. Behind that siding, the sheathing is black, soft, or gone. Sometimes the bottom of the wall framing is soft too.
Nobody saw it because the siding looked fine from the lawn. This post explains why that junction fails, what correct siding installation looks like at a masonry stoop, and what we do when a stoop rebuild uncovers rot.
Why the siding-to-stoop joint fails
A stoop is a horizontal slab of concrete or masonry pressed up against a vertical wall. Every rain, water lands on the stoop. Snow sits on it for days. Some of that water runs off the front. The rest moves toward the house, because stoops are often pitched slightly wrong or have settled toward the foundation.
If the siding ends at or below the stoop surface, the bottom edge of the siding sits in that water. Vinyl, wood and fiber cement all handle this differently, but none of them handle it well. Water wicks up behind the siding, into the sheathing and the bottom of the wall framing. Capillary action pulls it higher than you would expect.
Then the sun hits the siding and heats the cavity behind it. The moisture has nowhere to go but into the wood. Repeat for ten or twenty years.
Vinyl siding is the worst at hiding this, because vinyl itself does not rot. The siding looks new while the wall behind it is failing.
The three details that have to be right
Clearance
Siding should stop above the stoop surface, leaving a visible gap. The bottom edge of the siding should never touch masonry, and it should never be buried behind it.
Siding manufacturers specify this clearance in their installation instructions. The number is different for vinyl, fiber cement and wood, and it can also differ for horizontal surfaces versus roofs. We are not going to give one number here. Check the installation instructions for the specific siding on your house, or ask your installer to show you the clearance requirement for the product going on.
The gap looks like a mistake to some homeowners. It is not. That gap is what lets the bottom edge dry.
Flashing at the base of the wall
Above the stoop, behind the siding, the wall needs a water-resistive barrier, often house wrap, lapped correctly so any water that gets behind the siding runs down and out. At the bottom, a piece of flashing should direct that water out over the top of the stoop or the foundation, not down behind the stoop.
When a stoop is poured against a wall with siding already installed, there is no way to install that flashing properly. The concrete is in the way. That is why we flash the wall before a new stoop goes in, not after.
Kick-out flashing
Many front stoops sit under a porch roof or beneath the edge of the main roof where it meets a wall. Where a roof slope ends against a vertical wall, the water running down the roof edge needs a kick-out, a small angled flashing that throws the water into the gutter instead of letting it run down the siding.
Without a kick-out, a concentrated stream of roof water runs down the wall and lands right above the stoop. That is one of the most common causes of the rot we find. The fix is a few dollars in metal, but it has to be installed when the roof edge or siding is open.
What we find during stoop rebuilds
Here is the pattern we see when a stoop comes off the house. Our post on whether to rebuild or resurface a stoop explains how we decide that, and this is one of the reasons we lean toward rebuilding when the stoop is tight against the siding.
The old stoop comes off and the bottom of the wall is exposed. The siding was run down behind the stoop, so the bottom course is wet and dirty. We remove a couple of courses of siding to see the sheathing. The sheathing at the bottom is dark and soft. Push a screwdriver into it and it goes through.
Sometimes the rot stops at the sheathing. Sometimes the bottom plate of the wall and the ends of the studs are soft too. Sometimes the rim board at the floor framing is involved. We do not know until the siding is off.
This is also where we find the old house wrap either missing or lapped backward, and no flashing at all at the base.
What the repair involves
Open it up
Siding comes off the affected area, usually a few courses above the stoop and a few feet to either side of where the rot shows. We keep going until we reach solid wood all around.
Replace what is rotted
Rotted sheathing is cut out and replaced with new. If framing is involved, soft sections of bottom plate or stud are cut out and sistered or replaced. This is carpentry, not siding work, and it is the part that makes a stoop job a general-contractor job. Our post on the foundation-up general contractor approach explains why we would rather handle the whole junction than hand off half of it.
Wrap and flash
New house wrap goes on, lapped so water runs down and out. Flashing goes at the base of the wall, directing water out over where the new stoop will sit. If a roof edge meets the wall above the stoop, a kick-out goes in.
Build the stoop with a gap
The new stoop is built with its top surface below where the siding will end, and pitched slightly away from the house so water runs off the front. The joint between the stoop and the foundation wall gets sealed with a flexible sealant, since the two will move differently.
Reinstall the siding
Siding goes back on, ending above the stoop at the clearance the manufacturer calls for. Trim and J-channel are set so they do not trap water against the wall. The gap stays visible.
Checking your own stoop
You do not need to pull anything apart to get a sense of this.
Look at where the siding meets the stoop. Can you see a gap, or does the siding touch or disappear behind the concrete? Press on the siding a foot above the stoop. Does it feel solid, or does it give? Look at the stoop surface after a rain. Does the water run off the front, or sit against the house?
Look up. Is there a roof edge that ends against the wall above the stoop? Is there a kick-out flashing there, or a dark streak down the siding where water has been running?
If you see siding behind concrete, soft spots or a streak down the wall, the sheathing is probably already wet.
When to fix it
The cheapest time is when the stoop is already being rebuilt or the siding is already being replaced, because the wall is open anyway. The second cheapest time is now, before the rot spreads into framing. The most expensive time is after the floor framing is involved.
If you are planning a new stoop, make sure whoever builds it talks about the siding above it. A new stoop poured against the same trapped siding will produce the same rot.
Rebuilding a stoop or replacing siding?
JDG Concrete & Construction in Centereach does masonry stoops and siding under one license, Suffolk County Home Improvement License #HI-68303, so the junction between them gets done once and done right. Call or text (631) 672-1618 or request a quote.
Frequently asked questions
How much gap should there be between siding and a concrete stoop?
Siding should stop above the masonry, not sit on it or behind it. Siding manufacturers publish a minimum clearance to hard surfaces in their installation instructions, and it is generally a visible gap of an inch or more. Check the instructions for your siding product, since the number differs between vinyl, fiber cement and wood.
Why is the siding near my front steps soft or bubbling?
Water is getting behind it. Rain and snowmelt sit on the stoop, wick into the bottom edge of the siding, and soak the sheathing and framing behind it. Over years that sheathing rots. Vinyl siding hides it well, so the first sign is often a soft spot you feel when you press on it.
What is a kick-out flashing and why does it matter at a stoop?
A kick-out is a small angled piece of flashing at the bottom of a roof-to-wall joint that pushes water into the gutter instead of letting it run down the wall. Many stoops sit under a porch roof or roof edge. Without a kick-out, roof water runs down the wall and ends up behind the siding right above the stoop.
Do you have to remove the stoop to fix rotted sheathing?
Not always. If the stoop is sound and the rot is above it, the siding comes off and the sheathing is replaced from the outside. If the stoop was poured against the house with siding trapped behind it, or the stoop itself is failing, removing or rebuilding the stoop is often the only way to reach and properly flash the wall.
