When you discover a gravestone whose base is broken, it may be necessary to make a new one with a recess in order to reset the stone properly.  Here are instructions for constructing a form with a recess into which the stone may be set.  This example is for a stone 24" wide, 2" thick at the bottom,  and 36" high.

Construct a box out of 1/2" plywood or similar material.  Note: All dimensions are inside.

To calculate side A of the box, add the width of the stone (24") plus 6" for the ends plus 1" for the mortar joint (31").

To calculate side B of the box, add 6" (3" on each side of the recess), plus the thickness of the stone (2"), plus another 1" to give some space around it for the mortar (9").

To calculate the depth of the box, first calculate the depth of the recess (rule of thumb -- for a 36" high stone, the depth should be approximately 3.5".  Beyond 3.5' of stone height, for each foot higher, add one inch to the 3.5 for the dimension of the depth of the box.)  Then double the dimension determined above for the dimension of the bottom of the recess to the “floor.” In this case, the recess depth should be 3.5" for a 36" high stone, plus the 3.5" from the bottom of the recess to the “floor,” equals a depth of 7" from the top of the box.

To construct the box, cut a bottom for the box.  In this case, the dimensions of the bottom are 31" x 9".  Sides and ends mount to the outside of the base piece.  Use sheetrock screws to fasten sides and ends to the base.  Whatever material being used for these forms, you must add the thickness of the material to the sides and ends in order to get the proper inside dimensions.

Construct the recess form.  Note: All dimensions are outside.

 Side C of the recess form is the width of the stone plus 1" for the mortar joint (25").

Side D of the recess form is the thickness of the stone plus 1" for the mortar joint (3").

Side E of the recess form is 3.5" (for a 36" high stone).

Summary: The outside dimensions for the recess form are 25" x 3" x 3.5" deep.

Filling the form:

IMPORTANT: Before shoveling the concrete mix into the box form, some type of material should be used to keep the concrete mix from binding to the form.  Lining the forms with 6-mil plastic works well, or spray them with silicone lubricant or brush on linseed oil.

This form will require one 80# bag of concrete mix.  Follow the mixing instructions carefully. When the instructions call for one gallon of water, use one gallon only.  Shovel the mix into the box form until it is 3.5" deep. Tamp frequently to prevent voids.  Place the recess form into the box and center it. Hold it in place with a cross piece while filling the ends. Change the cross piece to run the full length (and more). Complete filling the form with the recess piece firmly in place.

Check your time. In about an hour, the recess form should be removed. It should come out easily leaving the depression intact. If left too long, the form will become stuck and you will need to take measures to remove it forcibly (to be avoided at all costs).

The casting needs to cure for about a week. Remove the casting from the box form in about 3 days. Moisten the casting once a day, covering it with a tarp or 6-mil plastic or similar cover.

If, after reading this, the logic of determining the dimensions still escapes you, call me at (413) 584-1756 or send me an e-mail at oakl@javanet.com with the dimensions of your stone.  I will be glad to make the calculations for you.