Installing a Sub-Top for Stone or Werzalit Tables

Introduction

A sub-top is a piece of plywood or MDF (medium density fiberboard) that you glue to the underside of a stone table top. The sub-top is used to attach the table base to the stone table top, and also to help support the stone table top and prevent it from cracking. For Werzalit table tops, a sub-top is recommended for outdoor use, so you do not penetrate the table and break the moisture seal. (The photo above shows our J24 table base with a granite table top).

We recommend using a sub-top for all stone tables, so you do not have to drill directly into your stone piece. Epoxying the stone directly to the table base is not recommended.

We recommend using wood that is at least 3/4” thick for your sub-top material. This will give you enough room to use sturdy screws, without adding too much weight to the already heavy table top. For outdoor tables, we recommend using exterior grade plywood or MDF.

Necessary Supplies:

• Stone Table Top
• Heavy Duty Table Base
• 3/4” Thick (or thicker) Plywood or MDF, cut to size.
• Construction Epoxy
• Clamps with rubber ends to hold stone and sub-top together while epoxy dries

Step 1: Cutting the Sub-Top to Desired Size and Shape

The size of the sub-top will depend on the size and shape of your stone table top. Generally, you’ll want the sub-top to be the same shape (round, square, rectangular) as the stone table top. If you have a square or rectangular table, your local hardware store will likely cut your sub-top to size for you when you purchase the wood. If you have a round or irregularly shaped table, you’ll likely need to cut your own sub-top or hire a professional.

The sub-top can be smaller than your stone slab. Generally speaking, your sub-top can be inset 6-8” on each side. For example, on a 36” x 48” table top, you could have a sub-top that is 28” x 40”. You’ll want to consult with your granite fabricator or contractor for exact specifications.

Many people also choose to paint their sub-top and give it a beveled (angled) edge, to make it look even more finished, and help it disappear so as not to be noticeable under the stone.

Step 2: Clean & Prepare Your Stone

You’ll want to clean the underside of your stone, to make sure it is free of any residue or debris that could prevent the epoxy from sticking properly. Start by using a soft cloth with warm water, then dry, and wipe with diluted isopropyl alcohol.

Step 3: Attach the Sub-top to the Stone Table

Once you’ve made sure that the underside of your stone is clean, it’s time to add epoxy. First, you’ll want to find the center of the table top. From the center point, measure and mark the corners (or edges for a round table) of the sub-top, so that once epoxied it will be centered on the stone.

Add a layer of epoxy to the underside of your stone, and to one side of the wood sub-top. Line up the sub-top with the marks you made in the last step, and press firmly. Attach the strong, rubberized clamps to the sub-top and stone so that it rests firmly in place. Refer your epoxy manufacturers directions for information on drying times (24 hours recommended).

Step 4: Attach the Table Base

Now comes the fun part! The final step is to assemble and attach your table base. We have video instructions on our website (TableBases.com). Just find your base on the website to locate video instructions for your specific model.

Once the base is assembled, place your table top upside down (sub-top facing up) on a blanket or other soft, non-scratch surface. Mark the center of the sub-top

With care, flip the table base upside down, so that the mounting plate rests on the sub-top. Please be careful, as the base will be top heavy in this orientation.

Center the table base and make sure it lines up with the edges of your table (for round tables, the base just needs to be centered). Once you’ve made sure the base is in the correct position, secure the base to the table top using wood screws.

Once the base has been screwed in, carefully right the table, and you are all done!