Q: I am contemplating filling in the open outer walls of my carport to convert it to a garage. The carport roof is supported by posts and...

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Q: I am contemplating filling in the open outer walls of my carport to convert it to a garage. The carport roof is supported by posts and beams. The posts sit up a few inches on concrete blocks that seem to be poured into the floor.

Since I will not be changing any of the structural portions of the carport, do I need to build a foundation under my new outer filler walls?

A: It is very common to see rot in these outer filler walls after several years if not installed correctly. When set directly on the concrete floor slab (without a foundation or raised “lip”), water inevitably finds its way to the bottom of these walls. Water comes in off cars, water gets in from outside when the slab settles and allows ground and rainwater to drain onto it and water gets in from leaking gutters and downspouts.

The level of the soil gets built up over time when you add beauty bark or mulch, and before you know it, water runs right at the bottom of this wall with nothing to stop it.

Foundations and concrete blocks can get the wood physically up off the level of the floor or ground and keep it dry. Enclosed porches, garages or other spaces built over previously open concrete floors have this leakage and rot issue in common; they are almost impossible to keep dry.

But a foundation wall or a row of concrete blocks adds complexity and expense to what once was a fairly simple project.

Assuming you do not have, or anticipate, drainage issues into or out of the garage, then simply building the filler walls to prevent rot should be sufficient.

Absolutely build the bottom sill plate of treated lumber. Non-treated wood will rot in only a few years.

Do not put drywall on the interior near the floor. Keep the siding well off the ground (at least an inch) if it is wood or wood products. Consider cement board siding for best results.

Q: I have continuous aluminum gutters. Several of the joints are leaking at the inside corners. I have tried caulking and silicone from the outside (lower). This looks bad and doesn’t seem to be working. Got any better ideas?

A: Gutter sealant can be bought at any hardware store in a squeeze tube or 11oz. caulk tube. Pick a day when we are not expecting rain for a few hours (every other July 26th might work).

To do it right requires climbing up on the roof or a ladder. Make sure the rivet holding the adjoining sections of gutter is secure, and the joint is flush and tight before proceeding.

Also make sure the gutter is secured well to the rafters or fascia boards. Tighten the gutter before attempting a repair.

Clean the area to be sealed with a rag. Take two sponges and build a dam on either side of the work area. Smear your gutter sealant into the crevice and let it dry the amount of time directed on the package.

Darrell Hay is a local home inspector and manages several rental properties. He answers readers questions. Call 206-464-8514 to record your question, or e-mail dhay@seattletimes.com. Sorry, no personal replies.