How to secure a an entry door frame on a 1925 Marble Threshold?

[Neil Covington]

I'm in the process of rehabbing a 1925 rowhome in Baltimore City. A large block of solid marble was used for the front door threshhold. It is around 5 feet long, 4 inches thick, and 8 inches wide.

The problem I have run into is that the door frame is not securely fastened to the marble. This allows the bottom of the frame to slide around on top of the marble.

What is the best way to fasten a door frame to marble? Obviously I am very worried about cracking or damaging the marble, and I also do not want to use a repair technique that will detract from the appearance of the entryway.

The best technique I have come up with is drilling straight down into the marble and dropping in a bolt through the wood around the frame and into the marble. this bolt would be just large enough to fit snug in the hole without putting pressure on the marble. Trim would be placed on top of the bolt.

Any ideas or suggestions would be greatly appreciated. Or if you think the idea that I had is good, how does one go about drilling into marble? How can I be sure that I don't crack it?

Thanks so much in advance for any suggestions or insight you can offer.

-R. Neil Covington [e-mail]

PS -- A picture of part of the threshold is at

Unfortunately a previous owner painted the marble, which is another issue I will have to resolve.

[Tom]

Why fasten it at all, except for a good caulking to keep out the weather? The proper jamb fasteners should be enough to keep it still. Is it not flat upon the marble? If not, you should check for level and plumb, and if it's still off the floor, shim appropriately the full width of the threshold, and then caulk to the marble. Oh, and PAINTED THE MARBLE?? Gotta love 'em. Not. Tom Work at your leisure!

[Charles Spitzer]

re: drilling marble:

marble is pretty soft. i'd probably use a hollow core diamond drill bit. make a dam out of clay around it, fill with water, and go at it. keep filling the dam with water as it goes away. put a bit of antifreeze in the water to help cool the bit. don't apply steady pressure, but tap the bit against the stone, drill for a few seconds and back it out to let the water get in there to flush out the swarf and cool the bit.

re fastening the frame to the marble:

drill, drop in a bolt, fasten the bolt to the frame with the straps they use to fasten pipes to cement walls. you might want to put some epoxy down in the hole to hold the bolt firm. you can get that in the wall framing dept of home depot, along with the threaded bolts that are commonly used for fastening the bottom plate of a wall to a foundation.

paint stripper may remove it, however, marble is porous (so the paint will have a good grip) and can stain (so the stripper may leave marks, along with unremoved paint).

regards, charlie cave creek, az