Drywall tape cracking can be serious problem
Q. We are experiencing problems with our cathedral ceiling -- cracking and wrinkling along the seams, along the peak and at the sides where the ceiling meets the wall. One contractor recommended to repair it with flexible drywall tape, but I am concerned that that may not be sufficient to fix the problem, and that we should consider the closed-cell polyurethane insulation you mentioned in a recent column. How do we find the right contractor to assess and fix the problem? I don't know if there is a specialty I should look for or what questions to ask. I would be glad to pay a consultant for advice but don't know how to go about finding one. I would appreciate any help you can give me.
Via e-mail
A. Drywall tape separating and wrinkling usually indicates that there's movement of the supporting members. This can become a serious problem, as warm, moist air can convect into the rafter spaces through the resulting cracks unless there is a very effective vapor retarder -- which is seldom the case because its installation requires extreme care that's not commonly achieved in normal construction. Assuming you have fiberglass insulation, this convected air reaches the cold roof sheathing and condenses. No amount of ventilation can overcome this overload, and rot will result.
Have you noticed any water stains anywhere on the ceiling? If there is a plastic vapor retarder, these stains are usually found where the ceiling meets the walls at the base of the cathedral ceiling. You haven't said where you live. Check with your utility providers, as they may be able to direct you to state- or local-energy specialists, if they do not provide the service themselves. You will need a specialist who is very familiar with construction practices.
Replacing the fiberglass insulation with closed-cell polyurethane foam will eliminate the condensation problem, as this type of insulation stops all air movement. If you choose to do so, be sure that the contractor is thoroughly familiar with the tricky process of removing the fiberglass without tearing the ceiling down and is highly qualified in the application of the foam. There has been a surge of people getting into the business who have very little experience with the chemical process and spray the wrong mixture. New federal guidelines have caused a change in the chemical formulation, and it takes very experienced people to spray the insulation under these guidelines. Above all, make absolutely sure that whoever you select does not sell you on the use of Icynene, an open-cell polyurethane foam that should never be used in cathedral ceilings.
Q. We are planning on installing ¾-by-3½-inch red oak flooring over a grade-level concrete slab. The house is over 40 years old, and we live in the northwest suburbs of Chicago. Our contractor plans on putting the moisture barrier over the subflooring instead of directly on the concrete. We were also told by a couple of contractors that we could use ½-inch subflooring because there are patio doors that would be too low if we use ¾-inch.
Is all of this OK? If not, what are the disadvantages to the placement of the moisture barrier and the ½-inch versus ¾-inch subflooring? The What is the optimal number of polyurethane coats for a family room floor, and is there one type that is better than another for a floor that gets a lot of cross traffic, including traffic directly from the outdoors? Also, since we seldom use our air conditioner and the humidity is relatively low at this time, how important is it to have the wood in the house for a week or two with the windows and doors closed?
Via e-mail
A. It is best to put the vapor retarder directly on the concrete slab. Another choice worth considering is to apply DRYLOK Concrete Protector with SaltLok on the bare, clean concrete. The manufacturer says that it prevents moisture in vapor form from coming through the sealant's film, which is what you want. I assume that there is no water problem in the room, since you say it is a grade-level slab; installing a wood floor in an area subject to leakage could be disastrous.
You haven't said, but will the plywood subfloor be applied directly over the concrete, and will it be fastened with power shots? Neither plastic nor DRYLOK Concrete Protector would be compatible with an adhesive. Or is there room for sleepers (wood pieces to which the subfloor is attached)? Since you mention patio doors, I assume that they are set on the concrete and there is no room for raising the floor with sleepers. In either case, ½-inch plywood is sufficient since the strip wood flooring you are planning to use is very rigid. It is always best to let the wood acclimate to the ambient conditions. It should be laid so as to allow air circulation. An experienced floor installer will know how to do this. For a durable finish, use a gym finish. Your paint store may not stock it but should be able to order it. They may also advise you on the product they recommend. For instance, Benjamin Moore slow-drying, oil-based urethane would do well. It comes in flat, satin and gloss finish. Keep in mind that the slower the drying process and the more coats you apply, the more durable the product will be. You should consider a minimum of three coats.
© 2007, United Feature Syndicate, Inc.