Are cement block cracks serious?

Q. We have a 1950s-built home on a sandy lot where most of the homes have cement block basement walls and many have had to be reinforced. Our walls have some cracks, mostly along a horizontal seam.

We've lived here for seven years and the cracks do not appear to be growing. Can we fill those cracks with some sort of filler? We're concerned about resale and assume this issue needs to be addressed.

We did have a basement specialist visit who said the situation was dire and tried to sell us a very expensive fix. We're doubtful since the cracks are not growing that we need to do this. Thoughts?

A. The cracks were caused by frost pressure at some time in the past. This is a common problem. I have seen similar cases in houses built on sandy soils. The sand may be very fine and, as a result, does not drain as fast as a coarser material does.

In the fall, following a significant rainfall, the temperature may have dropped very fast to below freezing, which caused the saturated sand to freeze and expand, and apply enough pressure on the block walls to push them in.

These cracks usually happen about three or four courses below grade, and as long as they are not more than a half inch wide, and no movement has occurred in the seven years you have lived in the house, there seems to be no reason to be overly concerned. The walls seem to have stabilized and there should be no need to do anything to them.

But if they are wider than one-half inch, consult a structural engineer for his or her opinion on the need to perform repairs. However, keep in mind that another set of similar conditions - rain followed by a sudden deep freeze - is always a possibility, and it may aggravate the existing situation.

My guess is that your block walls are only 8 inches thick. Had they been built with 12-inch blocks, as required by building codes for foundations deeper than 5 feet, they might have resisted the mild frost pressure, which yours encountered.

This condition is seldom seen on concrete walls, although I have seen such walls with significant cracks, but they were in houses built in heavy soils and backfilled with the native soil instead of coarse material.

It is often best to leave the cracks alone in the early years following their occurrence as the walls may straighten up when the sandy soil dries up if this does not result in the sand settling down. But since no movement has occurred in seven years, you may want to have a mason fill the joints in for aesthetic reasons.

Even if you get the joints filled with mortar, it may still raise questions at the time of a sale. But an experienced home inspector should be able to assess the severity of the cracks and reassure prospective buyers if need be.

You didn't say what the basement specialist offered as a fix. There are several ways to repair cracked block walls from simply stabilizing them to bringing them back to their original form. The best fix, if one is indeed needed, is to fasten special fiberglass strips vertically several feet apart on the block walls. An engineer is best to specify the spacing between these strips.

Q. We have a paver brick patio with an outdoor concrete fireplace and sidewalk leading up to this area to enjoy the great outdoors. Behind the fireplace is an Amur maple tree that drops helicopters seasonally.

Unfortunately, they badly stain our paver bricks, fireplace and sidewalk wherever they land. It is difficult to keep up with removal of them. We have tried using OxiClean on these ugly brown stains but have had limited success even if we leave the product on overnight. Our paver bricks have a sealant that a professional applied recently but that top layer of sealant stains, too. HELP! What is the best way to remove these stains?

A. I hope the stains were completely removed before the sealant was applied, but if not, they are stuck underneath it.

I suggest you try to power wash the affected masonry and follow that with an application of ecoGeeks Oxy-Boost Oxygen Bleach (www.ecogeeks.com.) Be sure to follow directions.

If this process removes the recently applied sealant, a new penetrating sealant is advisable.

Q. A few weeks back, you had words of wisdom about how to get mold off a Trex deck. I have that problem so I carefully saved your answer. So carefully, that I have lost it.

I remember you recommended a long-handled wire brush plus some kind of cleaning solution. Would you mind repeating what cleaning solution you should use?

A. Here is a repeat of the earlier column, appropriately edited:

A very effective solution I have used and recommended to painters who have raved about it after using it is as follows: Mix 4 to 6 ounces of Oxy-Boost in a gallon of hot water to which add one-quarter teaspoon of dish detergent. Wash the deck boards with a stiff-bristle deck brush on a long handle. Oxy-Boost is now only sold in 5-pound, 10-pound and 20-pound containers (the 5 pounds does not show on their website, but they told me it is available by request).

Even the 5-pound box should be far too much, but Oxy-Boost does not spoil and it can be used for a lot of other cleaning jobs.

You can order Oxy-Boost at www.ecogeeks.com, or call to order it at (262) 898-1522.

Follow up on emergency sump pumps: "I noticed in your Sunday, Oct. 8, column, a reader's comment about water-powered emergency backup sump pumps. The reader had no experience with the pump as an alternative to battery backups. I am writing as a homeowner who has had a water-powered pump in my basement for over 10 years and it has worked well as a backup pump. Several times the water-powered pump has kicked in during a power outage, for as long as three days on one occasion. So I would recommend it as a good idea.

"The pump I have is called Water Commander and it is from Tane Corp. If anyone wants to check it out they are online at www.tanecorp.com."

A. Thank you for sharing your experience with us all. I, too, have had no experience with these water-powered pumps. They sound like a great thing to have if you are on town water.

And here is another one: (Edited for length and clarity) "If town water is used for your water supply - not well water - and the town has backup generators for use during power outages to keep the water flowing, I would suggest going to www.libertypumps.com. I bought and installed one in 2012 and it works as advertised.

"A licensed plumber is needed, as its installation requires cutting into the existing water supply and connection to the discharge system. This pump gives me terrific peace of mind!"

• Henri de Marne, a former remodeling contractor turned columnist and consultant, is the author of "About the House with Henri de Marne" (Upper Access Publishing). He continues to take questions from readers for this column and his website, www.henridemarne.com. Email questions to aboutthehouse@gmavt.net.