Traditional water table trim at bottom of outside wall.

Old House Remodeling:

Building Traditional
Water Table Trim
With Cellular PVC Lumber


In This Article:

New water table trim is fabricated from Azek cellular PVC trimboards and fastened to the house.

Related Articles:

Skill Level: 3+ (Intermediate and up)

Time Taken: About 4 Hours

By , Editor

This article is part of a series on siding replacement. The entire story can be found in Replacing Old Wood Siding and Trim With Low-Maintenance Materials - A Quick Tour


The water table trim is the white-painted pair of boards (red arrow) below the yellow siding. This trim creates a  visual "base" for the rest of the exterior.

Today most builders simply begin the siding right above the foundation, but in earlier times (pre-Modernist, pre-WWII) it was common to employ some sort of horizontal band, typically a different color than the siding, to visually distinguish the house from the foundation. Think of the water table trim as analogous to a wallpaper border at the top of an interior wall... it provides a visual separation of two areas.

Original siding on old house, with peeling paint.

The paint flaking problem was the worst on the west side of the house. The house had been painted eight years earlier, and now it looked... awful.

The top piece of the water table, which I call the "lookout", was badly cracked because it had lost most of its paint.

Notice the chewed up appearance of the board above the basement window. We believe this opening was once a coal chute, and decades of shoveling coal into the basement resulted in shovels nicking the wood, and this wear-and-tear.

At the corners, the water table trim sections met at a mitered joint. Most of these joints had opened up from years of wood swelling and shrinking.


This is the northwest corner. Earlier we had removed the siding and water table on the north face. There is a short piece of water table trim from the corner to the porch deck.


Using a pry bar I removed that short piece. It didn't put up much resistance.


There were a lot of small cracks at the ends. This is probably a sign of repeated wetting and drying of the wood, causing the wood fibers to swell and shrink and eventually become disconnected from each other.


These cracks were all over the back of the wood.

This is common with old houses. The exterior wood components warp and twist with seasonal humidity changes, the paint flakes off and lets the wood get wet. As I just mentioned, repeated wetting and drying causes damage to wood, even if the wood is never wet long enough for rot to occur.


Maybe you can understand why over the years I've grown reluctant to use wood on any outdoor finished surface. I like wood. Wood is an awesome material, but it just doesn't last very long when it's exposed to the elements. Of course, some people would say "you need to keep it painted, then it's not exposed"... but that's my point. Exterior wood requires too much painting maintenance.


Getting Started:

In conjunction with the foam insulation, we fastened a strip of plywood to the base of the wall. This will act as a nailing base and more. (See the article on wall preparations)


At this corner there was gap behind the old water table trim visible between the red arrows.

This kind of gap creates a highway for bugs and possibly mice to enter the house. And it lets in cold air.

I slathered a bunch of caulk over this area to seal it. Larger gaps might require some wood filler blocks.


Making The Water Table Trim From Azek®:

The piece of Azek shown here was about 9 feet long. Azek comes in 18 foot lengths, and when I buy it I normally cut it at the lumberyard into lengths closer to what I need. In this case I simply made some scarf joints to connect the short pieces together.

I set up a table saw in the driveway, with a couple of outfeed stands to support the material. These are Ridgid Flip-Top outfeed stands, and they work well because Azek is a lot floppier than wood.

I ripped a piece of 1x12 Azek on a 10 degree bevel. The piece on the right will be the vertical water table board, and the off-cut will be used for the "lookout" board.


I ran the off-cut through the saw, with the blade still tilted 10 degrees. Now the fence is set closer to the blade.

Cutting Azek cellular PVC trim on table saw.


Water table trim before assembly.

These are the two components of the water table trim.


I have two kinds of glue that work with cellular PVC trim. On the left is ordinary PVC cement used for plumbing. This costs about $5 at Home Depot.

On the right is Azek Adhesive, which had to be special-ordered from a local lumberyard. This one-pound can costs about $20. Ouch. But it's useful.

Azek PVC trim cement and pipe cement.


Gluing Together Azek:

I laid the boards close together so there would be no fumbling after the glue was applied.

Using the dauber I applied a coating of glue along the entire top edge of the vertical board.


Then I applied a film of glue along the back 3/4" of the lower side of the lookout piece.

This is tricky because PVC pipe cement dries so fast that there is little time to spare.


Nailing PVC water table trim.

I pushed the pieces together and shot some finish nails through the lookout piece into the vertical board. I nailed it about every 12 inches.

I also could have clamped these pieces together, but that takes longer and the glue will be dry before I'm done.

It might be better to have two people, each with their own dauber or brush, to apply glue, because I had problems with glue drying too fast, and I had to apply more as I was nailing the boards together. The benefit of pipe cement is that it fully hardens in a few minutes, so the assembly can be cut into pieces right away.

Using Azek Adhesive is easier because it doesn't dry so darn fast... it allows perhaps 10 minutes of "open time", but it can take hours to fully harden.

Using the dual-bevel slide miter saw I was able to easily cut the miter on the end.

Without a slide miter saw I would have to cut the ends before gluing the pieces together.



The blade was about to hit one of the nails. Good thing I stopped to check!

I re-cut this piece slightly to the side of the first cut.


I had previously assembled this short piece of water table.

After carefully checking how well it fit with the long piece, I used 2-1/2" finish nails to fasten it to the house.


I applied some Azek adhesive to the cut end of that short piece.

This glue looks yellow-brown because earlier I touched some tar paper with the dauber and the solvents dissolved some of the asphalt, giving the whole can of glue a yellowish tint. It works fine... actually, the color makes it easier to find any drips of excess glue.


While my helper held up the other end of this 9-foot-long water table assembly, I aligned the corners and shot in a couple of finish nails.

Fastening cellular PVC trim with nail gun.


Then I used a brad driver with 1-1/4" brads to hold the ends tightly together.

It's important to fasten these joints quickly, before the glue dries.

I wiped off the excess glue with a paper towel.

When these joints are glued and nailed they are really strong. I have glued together test pieces and broken them, and usually the glue is stronger than the plastic.


The other end of this section of water table trim:

I purposely made the lookout shorter than the vertical board. It's better to keep the joints away from each other.

Notice that both of these boards have beveled ends instead of simple square-cut ends. These will be scarf joints, which are better than simple butt joints.

With the slide miter saw I could have easily just assembled several long sections of trim and then made an ordinary scarf joint to connect adjacent sections together. But I wanted to show this method.

From here I continued to the next corner by installing the boards separately, the vertical board first, with the lookout added next.

The left-hand corner.

Actually, I installed that short piece of trim before I completed the long run.

It's often easier to fit a piece of trim in between two existing pieces, especially when the joints are angled (i.e. one end is a miter, the other end is a scarf joint, which just means that the previous board was cut on a bevel instead of being square cut.


The completed long section of water table trim. This is just over 16 feet long.


Next we began installing the fiber cement siding, but that's a complete article in itself.


West Side Story:

On the west side of the house I did things a little differently.

I started off the same way...


But I had to leave out a section of the vertical board to go around the electrical service entrance.

We are planning on having the overhead wires replaced with underground service...


...and when that happens I will just slip this piece of Azek in place.


I was able to run the lookout board behind the service entrance conduit.

Note the gray conduit and box to the left of the window. That is for the telephone line. I simply opened the plastic box and removed the mounting screws. I cut a notch in the lookout part of the water table, and let this box flop around in the breeze for a couple of weeks while we worked on the siding.

When everything was done I fastened the box to the wall again.

One advantage of fiber cement siding is that you can fasten light-weight objects to it. Vinyl siding can't really support anything being attached to it, though I've seen people try.

I tried something different here. On the table saw I cut a very small strip of Azek, about 5/16" square. Then I glued and brad-nailed it to the lookout board.

This will act as the "kicker" piece that is needed for the first piece of fiber cement siding.


The completed water table.

We nailed a sheet of felt to the wall.


Then we installed fiber cement siding.

The new water table trim looks so much cleaner than the old wood trim. One drawback of cellular PVC is that it looks too uniform. But I can work with that... I can add a few hammer dings to liven things up!


This is a drawing of the of the water table parts that I used in this project.


HammerZone's Recommended Trim Carpentry Tools



Tools Used:

  • Basic Carpentry Tools
  • Table Saw
  • Slide Miter Saw
  • Finish Nail Gun
  • Brad Nail Gun

Materials Used:

  • Azek Cellular PVC Trim, 3/4" Thick
  • PVC Cement
  • Stainless Steel Siding Nails, 2½"
  • Galvanized Finish Nails, 2½"

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Copyright © 2005

Written March 25, 2005