Q: I was just under the house during a rainstorm and heard drips coming from under the porch. What is in store for me?

A: Things may not be as bad as you fear. If your porch is well ventilated, you may have no damage at all. But if water has puddled for a long time, you could be in for replacing the mudsill or more.

If there is damage, the fix could be as simple as removing and replacing the damaged wood or installing a brace to beef up the substructure.

Most likely, a void in the porch structure is the cause of your leak. Be aware, though, that the source may not be isolated to the porch. Water may be coming through failed roof flashing or loose window or door trim.

To see if the wood framing is damaged it really doesn’t make any difference whether you inspect when it’s wet or dry. Whenever you crawl under the porch, take a screwdriver with you and probe the wood. You’ll know if it’s punky or not.

The typical concrete porch deck is a poured concrete slab on a wooden substrate. The steps aren’t solid concrete, either. They’re poured concrete, formed into steps over a wooden ramp. The bulk of the structure is wood. The need for costly repairs occurs over the course of many years as water finds its way through cracks in and around the slab and penetrates to the underlying wood frame, rotting it.

The best time to pinpoint the source of the drip is when it’s wet. First, do a thorough inspection. Look at the exterior, making sure to pay special attention to the angles where the porch meets the house siding and where the stair risers meet the treads.

If you see a crack, that’s a clue. Then under you go. Look for water stains on the wood. Once you’ve got the leak pinpointed, fix it.

The fix could be as simple as caulking a joint or crack to properly flashing the joint where the siding and porch intersect. If the leak is where the siding and the porch meet, the short-term fix is caulking the joint for now, but plan on installing proper flashing later. We suggest you give one of the new hybrid caulks a try.

A Fine Homebuilding article gives a good primer on the types and uses of caulk. According to the article, these hybrids are easy to apply with a caulking gun; they can be applied in extreme temperatures and can withstand rain almost immediately.

So in a nutshell, here are five steps to take:

  • Do an exterior inspection for cracks;
  • Go under the porch to pinpoint the leak source;
  • Seal the source with a hybrid sealer;
  • If the source is the junction where wall meets porch, plan to install proper flashing when the weather gets better; and
  • Make sure the entire porch deck is well sealed with a high-quality porch and deck paint.
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