advertisement

Not all concrete floors need to be sealed, but some do

Q: I regularly read your column in the Daily Herald and have been following with interest the recent inquiries about sealing concrete. We had our garage floor totally replaced with new concrete seven years ago. The contractor did not mention anything about sealing the concrete, and so this was never done. Is it too late or impractical to seal it now, seven years afterward, once the weather warms up? What preparation steps do we need to take since it is now "old" concrete?

A. Many garage floors are not sealed and hold out well, but if you decide to seal yours, the following steps should be carried out. It doesn't matter how old the concrete is.

The garage floor will need to be thoroughly cleaned using a commercial degreaser. It should also be thoroughly scrubbed with a strong solution of TSP-PF. Then rinse it well.

You have several choices. Sealers come in topical or penetrating form.

The choices of topical sealers are acrylic, acrylic/epoxy hybrid and epoxy. These sealers are film-forming, and need to be reapplied from time to time - every year or two or three, depending on the type used and the manufacturer's instructions.

Acrylic sealers are very easy to apply with a pump sprayer or roller. Two coats are needed, and they will produce a shiny look, unless you choose a matte finish.

Acrylic/epoxy hybrids are tougher and more durable than the acrylic sealers.

Epoxy sealers are more difficult to apply and are the toughest, but they require special preparation of the surface. They can only be applied with rollers, and they can be slippery when wet. It is best to have specialists apply epoxy sealers.

Penetrating sealers do not need to be reapplied, as they penetrate the concrete and seal all the pores, but they may not penetrate if the concrete is very dense and cannot absorb water. To test this, spray water on the floor and see if it sinks in or just beads on the surface.

If the water is not sinking in, the concrete is so dense that you really don't need to do anything.

Q. We did some kitchen remodeling this summer and replaced the fan/light hood over the range with an over-the-range microwave/fan/light. It vents outside through the kitchen wall through the same exterior flapper. Now that it's winter here in Pennsylvania, we are getting condensation inside the microwave, and when it's very cold, it turns to ice.

The outside flapper opens and closes and has a shield over it (to keep wind from blowing it open). It seems to be working OK. I looked into buying a new one - but they look the same as what I have. Is there a solution? Or should we vent into a filter and close up the outside opening? Nobody I've talked to has heard of this problem.

A. I have received several questions from readers suffering from the same problem over the years. This problem is often caused by the stack effect in two-story houses.

Warm air exfiltrates in the upper parts of the house, creating a negative pressure on the first floor. The needed makeup air finds the microwave venting to be one of the easier ways to equalize the pressure in the house.

It is possible that the original damper is either loose or not closing as tightly as it should. To check this, you will need to take the microwave down to see if this is the problem. Even the smallest gap can cause icing and condensation inside the microwave.

When you bought the new oven, did a damper come with the kit? If so, replace the existing one with it. But if you need to buy a new one of the right size, you should be able to do so in hardware or appliance stores.

Keep in mind that even with a tight damper, the duct is still an uninsulated tube through an insulated wall, so there is still the possibility that the condition will be only slightly improved.

An alternative is to have a service person make the necessary adjustment to the fan to blow inside, seal the outside vent with the appropriate material and fill the duct with insulation.

If you use fiberglass, apply a vapor retarder such as 6-mil plastic or one of the peel-and-stick tapes available in building-supply stores. Or carefully spray low-expansion foam in the tube. Be aware that this product expands; do not replace the oven until the foam has fully expanded and you have a chance to trim off the extra.

Q. Can you please mention the tool you suggested for freeing painted sashes?

A. The perfect tool for freeing stuck sashes doesn't seem to have a special name. It's sometimes referred to as "window-opening tool" or "window-freeing tool."

The thin metal blade is shaped like a pear and has serrated teeth. You insert it between the sash and the frame and wiggle it up and down until the paint bond is broken. You should be able to buy one in paint and hardware stores.

Q. When we moved into our house the front and back stoops were covered with outdoor carpeting. We recently removed it and are now wondering what to cover it with. Someone suggested tile and another said to recover it with carpeting. I really need help on this one.

A. You have not said what the stoops are made of. It makes a difference as to what is best to do with them - if you need to do anything after removing the old adhesive with boiling water.

Tiles would be very slippery. If the stoops are made of concrete, and you are concerned about their being slippery, there are metal stair treads that can actually be installed on any stairs, but my concern is that anything but concrete or pressure-treated wood may be adversely affected if the treads are exposed to the weather.

If you're interested in these metal treads, check this website: www.kofflersales.com.

Q. We recently were told by HVAC personnel of moisture/mold problems in the crawl space of our 25-year-old tri-level home.

Upon the initial inspection by our homeowner's insurance agent, it was agreed to have an engineer make a thorough evaluation of the cause. His report and pictures are attached.

We're wondering if you would kindly review this report and offer some direction as to the kind and scope of repairs necessary and the type of professional(s) that should be sought.

We would also appreciate your thoughts on how best to ventilate/not ventilate the crawl space (between the lower level and garage). There seem to be two schools of thought about whether it's a necessity or not.

A. You have received a comprehensive engineering report with which I am in total agreement. Most of the rim joist wetness and mold are caused by the moisture from the uncovered crawl space dirt floor migrating through the rim joists' fiberglass insulation, which is lacking a plastic vapor retarder.

The absence of vents is not the problem, as crawl spaces with proper floor moisture control should not be ventilated in order to prevent summer moisture from being absorbed by the framing and causing the problems visible in your home. This also requires proper vapor retarder installation covering the rim joists' fibrous insulation. If the rim joist insulation is done with rigid insulation, its perimeter should be caulked.

The engineer's report also singles out the absence of a kick-out diverter, where the addition roof ties into the original two-story house wall. As pointed out, this would prevent roof water from getting behind the siding and entering the house. A kick-out needs to be added.

It is evident that the builder who built the addition for one of the two previous owners made several errors, showing inexperience.

I suggest you hire an experienced general contractor who has a strong understanding of moisture problems and the damage they can cause inside walls.

It looks to me as if the vinyl siding will need to be removed, and the sheathing opened up where it has been damaged by the leakage. It is likely the insulation needs to be replaced. The studs should be checked for rot and possible structural damage. New sections of studding may need to be replaced or sistered to the damaged ones to preserve the integrity of the structure.

The crawl space floor(s) should be thoroughly covered with 6-mil plastic. The rim joists should be first allowed to dry, then sprayed with a solution of equal parts bleach and water, and allowed to dry again. If you choose to re-insulate them with fiberglass, cut the pieces 1-inch wider and longer than the measurements between the joists and the mudsill and floor sheathing. Fit the batts gently and tightly, making sure that they fit the entire space and are fully in contact with the rim joists. Cover them with 6-mil plastic stapled to the sides of the joists, the sheathing and the mudsill.

If you select rigid insulation, cut the pieces to fit tightly, press them all the way in to the rim joists and caulk their perimeter with polyurethane caulking to prevent bypassing moisture penetration.

Sorry for those problems caused by someone else's incompetence.

• Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. His book, "About the House," is available at www.upperaccess.com. His website is www.henridemarne.com. Email questions to henridemarne@gmavt.net.

© 2015, United Feature Syndicate Inc.

Article Comments
Guidelines: Keep it civil and on topic; no profanity, vulgarity, slurs or personal attacks. People who harass others or joke about tragedies will be blocked. If a comment violates these standards or our terms of service, click the "flag" link in the lower-right corner of the comment box. To find our more, read our FAQ.