Dear James: I want to install some glass block windows for security and privacy. Would a kit that uses silicone caulking be a strong as the regular mortar installation to deter a thief? — Donna G.

Dear Donna: Both glass and plastic block windows provide much more security than a standard casement or double-hung glass pane window. Although it is possible to break through a block window, it would take a long time and make a lot of noise that you or your neighbors would hear. Thieves seldom attempt it.

When installing a block window, don't forget about egress requirements in case of fire. There still must be at least one window that opens. It must have a minimum opening width of 20 inches and a minimum opening height of 24 inches. The window must have a minimum net clear opening of 5.7 square feet with a maximum sill height of 44 inches above the floor.

Installing individual glass blocks in mortar is the best method for security. An experienced installer can do this quickly, and hiring a professional might be your best option for windows that are visible from indoors.

For a utility room, a perfect, neat indoor appearance is not as important, so you might try to do it yourself. Even if the finished job does not look perfect, it will still stop a thief from breaking through the window. Also, it will seal out air and water leaks.

The first step to installing individual glass blocks in mortar is to select the type of glass blocks. For a utility room, a clear view outdoors is not important. Instead, select glass blocks with a medium surface pattern to provide privacy from outdoors but still allow diffused natural light to pass through.

Once you have the old utility room window removed and the opening cleaned out, it should take about half a day to install a glass block window using the mortar method. If you start having problems after installing a course or two of the glass blocks, you can stop there and seek assistance.

Determine how many and what size glass blocks you need to fill the window opening. Blocks are available in several sizes, so you will likely need a variety of sizes to properly fill the opening. The optimum gap between the glass blocks for the mortar joints is 1/4 to 3/8 of an inch.

The next step is to prepare the sill for the mortar and the first course of glass blocks. Coat the sill with a water-based asphalt emulsion to seal it, and let it dry for a couple of hours. Nail a polyethylene expansion strip to the header and window side jambs.

Lay the proper thickness of a mortar bed on top of the dried asphalt emulsion. Place the base course (horizontal layer) of glass blocks on this mortar bed, leaving the proper gap between each glass block. Using a rubber hammer or the handle of the trowel, tap them down into the mortar bed. Fill the vertical gaps between them with mortar.

Spread another layer of mortar over the first course of blocks, and place the second course on top of this layer. Tap them in place. It would be wise to install steel reinforcing rods between every second course of blocks. Spread only a half-thickness of mortar; place the rods, and spread the rest of the mortar so the rods are totally surrounded by mortar.

Before all the mortar gets too hard, smooth the mortar joints for a nice appearance. Clean out a gap around the perimeter, and fill it with packing material. Finish the perimeter with wood or aluminum trim.

Send your questions to Here's How, 6906 Royalgreen Dr., Cincinnati, OH 45244, or visit www.dulley.com. To find out more about James Dulley and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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