anchoring into old brick

I'm trying to install a mantle across an old, brick fireplace. The house is 130 years old, and the fireplace is of unknown age and origin. The bricks seem to be very prone to crumbling.

I sunk five masonry anchors into a cleat, and then mounted the mantle on the cleat. After a couple of minutes under about 80 or 90 lbs of load, two of the anchors had stripped, and the other three weren't looking real confidence-inspiring.

Does anyone have any suggestions about how to anchor into old, crumbly brick? Perhaps it's just not possible. Perhaps the better course of action is to support the thing from the bottom.

Any ideas?
Greg

 

Hi Greg, sounds like a marginal situation, however, there may be hope. There are different forces at work here. Imagine a 2" thick mantle with a single anchor in the middle. Any weight on the mantle would act like a nail puller by rotating downward with the force magnified by the ratio of the width of the mantle to the one inch thickness below the bolt. Now imagine a 6" mantle with the bolt at the top. A weight placed 6" out on the mantle would have only a one to one mechanical advantage. Then extend that distance below the mantle by installing ornate angle brackets. Essentially you will be eliminating the pulling force and relying on the shear strength of the bolts.

Now, to get a really good anchor in place, drill a 3/4" hole as deep as you can. All the way through if possible. Then insert a threaded rod with a nut on it. Support and fill the hole with mortar or epoxy. Install as many as needed.

enjoy the fire
Bud