Drywall crack’s cause key to correct repair material

Hey there, time traveller!
This article was published 31/03/2002 (8588 days ago), so information in it may no longer be current.

QUESTION — I realize this is not really your field, and I am hoping you can answer my questions or direct me to someone who can.

I have been experiencing some recurring cracks in the drywall in my home and have been advised to try a flexible-type filler to repair them. I purchased LePage’s Poly Flexible Filler only to discover it is not sandable.

The instructions imply it is more for outdoor use. Is there a trick to getting an invisible repair job on interior drywall with this or similar products? I have attempted to wipe it immediately with a damp sponge and end up removing as much as I applied. Maybe there is a better product on the market for this application. Do you know of it?

Thanking you in advance for any information or direction you can supply.

Bob Hunter, e-mail

Answer — Regular home maintenance, even cosmetic repairs such as patching and painting, are often much more difficult if the proper materials are not used. A simple patching job may be tremendously frustrating, as experienced by Mr. Hunter. Often, the reason professional repairs are so quickly done is the use of proper equipment and materials in addition to experience.

Over the years, I have experimented with many types of fillers, spackles and patching materials, often on the advise of professional painters, drywall tapers, and contractors. There are many different products on the market for many different types of applications, but most are similar compounds, which vary in strength, flexibility and brittleness. The filler used by Mr. Hunter may be for interior and exterior use and is likely very durable, but difficult to sand. It is not well suited for interior drywall repairs.

Determining the cause of the crack will help in deciding which is the proper repair material to be used.

Most cracks in drywall are caused by shrinkage in the sheet material and filler, or movement and shrinkage of the wood in the walls and ceilings.

Often, the individual sheets become slightly loose and fasteners may need securing prior to patching. If screw or nail heads, or loose filler covering them, is visible, they should be dug out and removed before continuing. New drywall screws can be installed with a screw-gun or electric drill, while pushing on the wall to ensure that there is no gap between the wall studs and the sheets of drywall.

If the cracks are small or hairline, they should be enlarged slightly with a putty knife to allow better adhesion of the patching material. The most commonly used material for these minor flaws is redi-mixed drywall compound.

This is available at all home centres and paint suppliers in various-size buckets and is very soft and easy to sand. It is applied in two or three thin coats on top of one another, allowing sufficient time for drying between coats. This method of application will ensure a smooth finish. The excess material and rough edges of the patches can be easily sanded with fine-grit sandpaper, taking care not to over-sand.

If the cracks are larger than one-eighth of an inch and above doorways, archways or windows, they are likely the result of movement and require a harder patching material. Drywall compound may be used, but must be accompanied by paper or fibreglass mesh tape to cover the cracks. This is a much more difficult method of repair for most homeowners. The tape will have to be secured properly to the wall and a larger area will have to be filled and sanded to achieve a smooth surface.

Most homeowners may prefer to fix larger cracks by using different fillers or additives that are harder and more durable than drywall compound. After removing any loose material and widening the crack, harder filler, such as that used by Mr. Hunter, may be initially used and allowed to dry. It can then be covered with successive coats of regular drywall “mud” to allow for easy sanding. I often add a dry powdered spackle or other quick-drying patch to redi-mixed drywall compound to increase the strength. Non-concrete floor-levelling compound is a favourite of mine, but must be mixed along with water into the mud in small quantities to prevent setting prior to application.

Using compounds produced by the same manufacturer will often prevent problems between dissimilar products. Starting on a small area and testing different materials together will be necessary to ensure they are compatible. All repairs will have to be painted with a primer to seal the patches and ensure good adhesion before painting with a finish coat. As with most small home repairs, practice makes perfect, and I suggest buying small quantities of different products to find the ones most suitable and easy to use for each application.

Ari Marantz is owner/inspector of Trained Eye Home Inspection Ltd. and is the public relations representative for the Canadian Association of Home Inspectors – Manitoba (www.cahi.mb.ca). Questions can be e-mailed or sent to: Ask The Inspector, P. O. Box 69021, 110-2025 Corydon Ave., Winnipeg, Man., R3P 2G9. Ari can be reached at (204) 291-5358.

trainedeye@iname.com