No visible means
By Brian L. Knight
It was only after I said "No problem"
to my sister's request for a shelf installed on the wall of her new house that
she dropped the other shoe. She wanted the shelf cantilevered from the wall
with nothing visible holding it up. "Simple," I said out loud, but I was thinking,
"how the heck am I going to do this?" I decided to use hardware bonding to install
the shelf. Even though the shelf only had to hold up Lori's bird house collection,
I figured that some day some little kid would want to do chin-ups on it, so
I installed it to last. Simply put, I drilled oversized holes into the 2"x 4"
wall studs and matching holes into the shelf stock. Then I glued the threaded
rod into the wall with WEST SYSTEM® epoxy so it protruded from the wall. When
this epoxy cured, I glued the shelf onto the protruding portion of the rod.
This type of installation is not easily reversible so I warned my sister that
if she ever changed her mind, there would be a major drywall repair job to do.
Hardware bonding to install a
I began by locating the wood studs and marked the wall with a chalk line
where the top edge of the shelf would go. The holes in the wall had to be perpendicular
to the wall surface or the protruding part of the threaded rod would be out
of alignment. I built a simple jig to help me guide the drill motor so the hole
was drilled perpendicular to the wall. I wrapped tape on the drill bit to remind
me that I had to stop before I drilled completely through the wall.
The 6/4 (1-3/8") pine stock I chose
for the shelf determined the threaded rod diameter. I used 1/2" rod with nuts
installed on it so the diameter of the hole had to be equal the distance across
the points of the nut (13/16"). Three nuts were installed on the portion of
the threaded rod bonded into the wall and two nuts were installed on the part
of the rod bonded into the shelf. The nuts center the threaded rod in the hole
and also create more frontal area at the point of highest stress- the place where
the threaded rod exits the wall (Figure 1).
Once the holes were drilled in the
studs, I dry fit the rods by pushing them into the hole. Next, I set the shelf
on top of the protruding rods and scribed the shelves to the wall. Once the
shelves fit the gentle curves of the wall, I set them on top of the threaded
rods and marked the location of the rods on the bottom surface of the shelf.
At this point, I was ready to permanently
install the threaded rod into the holes in the wall. I applied some vinyl electrical
tape around each hole as masking. I used WEST SYSTEM 105 Resin/206 Hardener
and thickened this mixture with 404 High-Density Filler. Then, I injected the
mixture into the hole in each stud using an 810 Fillable Caulking Tube, applied
some of the same mixture to the threads of the rod, and pushed the rods/nuts
into the wet epoxy.
The important part of this operation
was getting the nuts located properly. One nut was located at the end of the
threaded rod to center it at the bottom of the hole. Because the wallboard has
little or no ability to resist the shear load of the shelf, I located three
nuts back to back to back-jammed against each other-where the rod exits the
wall. The inner nut is able to bear against the wood stud for support while
the middle nut acts as a spacer to transfer load across the weak wallboard.
The outer most nut is bonded in the hole in the shelf. This stack of nuts transfers
the load from the shelf to the inner nut in the wall stud.
While the epoxy in the wall hardened,
I took the shelves back to my shop and used a drill press to drill the holes
to receive the threaded rod. I stained and varnished the shelves before permanently
installing them. Before gluing in the threaded rod, I dry fit the shelves to
be sure they fit where they belonged. If it had been necessary, I could have
enlarged the holes in the shelf to allow some adjustment room. The epoxy would
fill any gaps between the hole and the threaded rod.
I injected epoxy into the hole in
the shelf and slid it over the threaded rod/nut assembly as I had done previously
in the wall. I temporarily braced the shelf with shims and scrap plywood legs.
I also toenailed a few finish nails in the top of the shelf into the stud to
keep the wall edge of the shelf where it belonged. The next day, I removed the
braces and my sister loaded up her new shelves.
Epoxyworks 18 / Fall 2001
Copyright© 2002, Gougeon Brothers, Inc. All rights reserved.
Reproduction in any form, in whole or in part, is expressly forbidden without the consent of the publisher. EPOXYWORKS, Gougeon Brothers, WEST SYSTEM, Episize, Scarffer and Microlight as used throughout this publication, are trademarks of Gougeon Brothers, Inc., Bay City, Michigan, USA.
See the West System Manual for more instructions on bedding hardware.