Home repair: Water causes problems in foundation cinder blocks

Q. It’s no surprise, but after this past year of record snows and rain, we are having continuing moisture problems in the cinder-block partial basement of our 1970s-era ranch home. We used to get water in our basement when the heavy clay soils around us got saturated. This summer we had a contractor install a perimeter drain and a new sump pump. He jackhammered the cement floor of the basement about 12 inches out from the wall, dug down about 12 inches, installed a perforated PVC drainage pipe wrapped in landscape cloth, and covered it with gravel. Then he cemented back over the top of the trench, leaving a 1- to 1½-inch gap filled with gravel right next to the outside wall. The pipe is pitched so that any collected water should run into the new sump.

Once this was all in place, we had the walls of the basement cleaned of the various molds that had been growing there for a number of years with a bleach solution at the suggestion of a “mold expert” who said the mold was not toxic but was of the “paint-eating” variety. Then we had the wall painted with two coats of Drylok.

The good news is that since the work was done, we have not had any more puddles of water in the basement. This is in spite of the recent heavy rain. With one dehumidifier running, we can keep the relative humidity around 60 percent.

The bad news is the paint is becoming discolored, and it’s possible this is mold growing back again. (See the attached photos.) The new paint was laid down less than two months ago. It’s also possible moisture is causing the paint to discolor.

How can we find out what this is and how to treat it? We’ve spent more than $5,000 on this project so far and are reluctant to proceed until we figure out if we still have a moisture problem that needs to be addressed. We have not tried getting at the moisture in the walls from the outside, as that sounds like a huge project involving moving trees and landscaping around the house. Is there anything else we might try to solve the moisture issue before undertaking a major outside project?

A. Before spending any large amounts of money on other fixes, the first thing anyone with foundation leakage should do is to look at the grade around the house to make sure there are no low spots or even flat grades.

Flower beds are also a possible cause because they usually are either flat or humped, which can trap water and allow it to get down along the wall. When it gets to the footing, water is trapped by undisturbed soil that may not drain, and it leaks inside.

Driveways, patios and walks that are flat or have settled and pitch toward the foundation are also a leading cause of leakage.

If improper grading allows surface water to penetrate through foundation walls or at the joint of walls and concrete floor, the water can fill the cores of hollow cinder or concrete blocks. If these blocks are waterproofed with any type of coating, water will build up within them and can cause untold misery in the main living quarters as it evaporates the only way it can. That is why I have advised my readers for years never to waterproof block foundations from inside.

In your case, the photos show the typical signs of water accumulation in the bottom rows of blocks. It tells me the contractor who did the under-slab drainage system did not drill at least quarter-inch holes in each block core in the bottom row to allow drainage of their cavities before pouring the new concrete over the drainpipe.

Drylok does not prevent mold formation, and peeling has been reported, as well as other failures.

You can find out if this is what is happening by drilling a few test holes at the very base of the block, just above the concrete floor. Be sure you use a star drill and a hammer or a cordless drill, as water may come surging out. Using a corded drill may cause electrocution.

Q. I’ve attached photos of the joists under the garage. Tell me what to do!

I know they’ve been like this for a while, but my husband was in charge of those outside jobs, so I didn’t worry. He died last year, and now I’m in charge. Under the garage is not enclosed. The entrance is ground level and at the other end, 3 feet above the ground. The ground is bare dirt.

I’m sure the ground should be covered with heavy plastic, but I don’t know what to do with the rest. Spray with something, or replace?

A. The photos you sent show rough-hewed rafters that seem to have come from a sawmill. In one photo, they really don’t look bad, unless the photo does not show their real condition. In the second photo, the beam appears to have some sort of growth on it, which I cannot see clearly enough to be sure what it is. So it’s hard to suggest what should be done, if anything.

You may want to consider having an experienced contractor take a look; whatever is there can possibly be scraped off. Applying a wood preservative on the beam — once cleaned of whatever is on it, if need be — and the joists is not a bad idea.

It’s a good idea to lay heavy plastic on bare soil, but since the perimeter is open, let natural ventilation take care of the rest.

Q. I had a retaining wall built several years ago that is somewhat covered with moss. Do you know of a product, other than a bleach solution, that will kill the moss? There is too much vegetation to protect from bleach. I have found Moss Max by Bonide to be useless. After I power-wash the wall, is there a product I can use to seal the pores so the moss roots won’t penetrate so much, making it easier to remove the moss?

Lastly, if I use such a product on my sidewalk, would it make it slippery and therefore unsafe to walk on when wet?

A. I assume your retaining wall is made of masonry. Powerwashing should remove the moss, but if it does not, you can either pick the blooms by hand or spray them with a solution made of three parts white vinegar and one part water. Give it time to kill the blooms, which will then be easy to scrape off.

Any type of masonry sealant you can purchase in masonry supply houses should work. Home Depot carries a good one made by Sika, which is also used to seal concrete. It should not make the sidewalk slippery.

Q. My home has terra cotta roofing. There are very few such roofs in the area. We are having trouble finding someone to help us learn why the left gutter still drops water into the bedroom doorway below the valley.

Could you offer any suggestions? We live in the Pittsburgh area.

A. Terra cotta, or clay tiles, can be damaged by the freeze-thaw cycle, which could be a problem in your area. If water permeates them, they can start leaking. The source of the leak may be hard to detect, as water can travel some distance before showing up. So you may blame the gutter, when it is possible that the water comes from one or more deteriorated tiles. It is also possible your gutter needs cleaning.

You may want to contact Santoro Tile & Marble Co., a distributor of terra cotta roofing, 522 W. Main St., Norristown, Pa. 19401; (610) 272-7511. Ask if they can recommend someone experienced in this type of roofing, as it requires special skills.

Ÿ Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Write to him in care of the Daily Herald, P.O. Box 280, Arlington Heights, IL 60006, or via email at henridemarne@gmavt.net. His book, “About the House,” is available at www.upperaccess.com and in bookstores.

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