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By Chris | July 14, 2010 - 4:47 am - Posted in How To, Marine Structures, Treated Wood

On his 4th voyage over to America, Christopher Columbus lost all of his ships to shipworms. All of them. Why was so little wood found on the sunken Titanic when they finally raised it from the ocean floor? You got it…shipworms. You got that right, right?

Mollusks, Actually

So what are shipworms…and why and how do they cause so much damage? Shipworms (also known as Pileworms) actually are not really worms at all, but are rather a type of clam that has very small shells used for boring into wood in saltwater.

A marine bivalve mollusk (with 65 different species)…they get their name for their long, narrow, cylindrical bodies – resembling worms. However, upon closer inspection, you will find a small drill-like shell. This shell has two halves with a gap between them, like a clamshell. In the gap there is a muscular foot that acts as a suction cup, holding the shell in place while it’s razor-sharp edges scrape the wood ahead of it. Shipworms have long tubes that stick out into the water so the worm can breathe, and can also seal the worm in the wood in cases of extended periods out of water…low tides for example.

Up To 6 Feet Long

shipworm (tereda)Also known as “Termites of the sea”, shipworms eat sawdust. The stomach of shipworms has a pouch for storing sawdust and an organ/gland full of bacteria that aide in digesting wood. The bacteria take nitrogen from the water and convert it to protein for the worms’ nourishment. The shipworm invades wood while still in the larval stage, making an entrance hall that is usually too small to see. It uses the shells on its head to burrow. The ridged, rough surfaces rub the wood away as the worm moves from side to side. This cuts away a perfectly circular tube that is just larger than the shell. The wormlike body follows behind the shell, producing a chalk-like substance to line the burrow. As they burrow deeply into the wood, they grow very quickly. As the worm grows, so does the burrow. Depending on the size of their homes, shipworms can range in size from 6 inches to as long as 6 feet.

Expensive Damages

Once a shipworm claims a home, it is there for life. A piece of wood may be infested with shipworm, but they will deliberately avoid each other’s tunnels. Instead they twist and turn their tunnels until the wood becomes a mass of tubes and holes, and eventually collapses. Shipworms are sometimes called the mollusk with the million-dollar appetite. These creatures are credited with single-handedly destroying the Hudson River piers in New York City. Researchers estimate that untreated timbers, such as pier pilings, exposed to Hawaii’s ocean waters will last less than two years.

A Positive Note

However, this incredible appetite has a purpose. Large amounts of wood get into the oceans by river deposits, forests and mostly, humans. Shipworms play an integral role in reducing the amount of driftwood in the world’s oceans.

How To Stop Shipworms

So, how do we stop the shipworms & protect our ships & wooden structures? By protesting at the White House? Not likely. Shipworms don’t like copper….so we can build using copper nails, or even copper sheeting. A cheaper and easier method is simply using CCA treated wood which contains copper (CCA = Chromated COPPER Arsenate).

Well, We Like Oysters

Or, we can eat them. In some places, shipworms are considered a culinary delicacy. In the Philippines, it is prepared as ‘kinilaw’ – eaten raw, with vinegar or lime juice & chopped peppers and onions…Similar to ceviche. The taste has been compared to a very wide variety of foods ranging from milk to oysters.

By Chris | October 23, 2008 - 12:25 pm - Posted in Marine Structures, Structural Components

Sites & Pages Dedicated to Covered Bridges (by State)

These sites and pages about covered bridges relate perfectly to the last LumberTalk post about wood bridges.

Wood bridges in New York.

Vermont’s covered bridges by county.

Covered bridges in Oregon by county.

covered wood bridge Harrisburg, TN Covered Wood Bridge

This covered bridge in Harrisburg, TN has an interesting history and the story explains a little about how covered wood bridges were built back in the day. The townspeople contributed money (willfully, not through taxes) and the town gave the rest.

I made a sketchcast about how to build a wood bulkhead and I wrote about how to build a wood retaining wall but I might have assumed too much about how much you know about the bulkhead materials I listed. They are slightly off the beaten path from “regular” building materials you’d find at your local hardware store so here is a breakdown of basic wood bulkhead materials.

Wood Bulkhead Materials List

Building a wood bulkhead is similar to building a privacy fence. You have posts (pilings), rails (wales), and pickets (sheets or sheeting). A bulkhead typically has great horizontal force applied against it, though, so it has more structural requirements than a fence. In order of front to back (water side to ground side) the parts of a wood bulkhead are:

  • Pilings (can be round or square)
  • Wales
  • Center Match (sometimes call “sloppy tongue & groove”)
  • Filter Cloth
  • Tie Rods
  • Deadmen
  • Top Cap
  • All the required Hardware (nails, screws, spikes, nuts, washers)

Attention: First, the materials required for YOUR wood bulkhead might be different from those I am showing below so please have your bulkhead designed and specified by a professional builder and/or designer. Also, be sure to use the proper materials for the best longevity. Using cheap materials to save money NOW is only wasting money in the long run. Use properly treated wood, galvanized or stainless hardware, and make sure the bulkhead is installed properly.

Treated Pilings

You can use round or square pilings. It is totally up to you. You might want to match your neighbors’ bulkheads or you might be concerned about costs (round pilings cost less). Either way, use properly treated wood – 2.5 pcf in saltwater and a minimum of .60 pcf in freshwater. For brackish (mixed fresh and salt) water, go with 2.5 pcf.

Round pilings - small ones

treated 6x6 timbers


Wales are the horizontal boards (like the rails on a fence). Most wood bulkheads have two but some will have three or more. Wales are connected to the land-side of the pilings and will have the center match sheets nailed to them. A very common size used for wales is 3×8. You should use the longest lengths possible to minimize joints, which can become weak spots. You should be able to find 3×8-20’s from most marine construction suppliers. Many other sizes are commonly use depending upon the sizes of the bulkhead and the forces applied to it. I have seen wood bulkheads with 8×8 wales.

treated 3x8 rough lumber for wales

Center Match

Center match are sometimes called “sloppy tongue & groove” because the joint is a little loose to allow for swelling in the water so the edges will not break with regular expansion and contraction when the boards alternates between wet and dry.

Center match is usually nominal 2×10 with actual dimensions of 1.5″ x 8.9″. That is, because of the groove each board only spans 8.9 inches – very important to factor into your bulkhead materials list. I have heard of numerous people making an extra trip to the dealer (or paying for another delivery) because they were 5 pieces short of center match.

treated 2x10 center match

Filter Cloth

Filter cloth is kind of like a very thick felt. The purpose of filter cloth is to stop silt and dirt from seeping through the spaces between the center match while allowing water to drain and relieve hydrostatic pressure from the bulkhead after a rain – it helps maintain a cleaner appearance and keeps soil behind the bulkhead where it should be. While some people use plastic for this purpose, I truly believe a quality geotextile filter cloth is better because it allows the water to drain. Filter cloth is cheap – use it.

Geo-Textile Filter Cloth for a Wood Bulkhead comes in rolls

Tie Rods

Tie rods support the structure from behind to keep it from falling forward (into the water). Tie rods will be connected to the pilings on one end (via hold drilled from the front to back of each piling) and to deadmen on the other end. They are simply long rods with about 12″ of threads on each end for a nut.

Builders usually use tie rods that are about 3 times as long as the exposed height of the bulkhead being built. For example, a 4′ tall wall will commonly use 12′ long tie rods. The come in diameters including 1/2″, 5/8″, 3/4″, and larger. Some people use cables instead of tie rods but tie rods are stronger and they can easily be tightened if needed.

galvanized tie rods


I have no idea why deadmen are called deadmen but I can make up some good stories about medieval times and using what you have to protect the castle if you want. 🙂

Dead men are treated posts – round or square and often cutoffs – used to “tie back” the bulkhead and support it from behind. Like the rest of the materials, the size of the deadmen used should be based upon the overall height of the wall and the load it bares.

new dead men.  These might be cut in half for a small wall.

Top Cap

Most top caps are made using a regular S4S 2×12. While they are not required, top caps will provide a little more structural integrity while giving the wall a more finished appearance from above.


Use galvanized or stainless steel hardware when building on or near water. Screws are better than nails but more time-consuming. Generally, you will need the following hardware for your bulkhead:

  • Tie Rods with 2 nuts and 2 washers for each
  • Spikes (60 penny nails) to attach the wales to the pilings
  • 16 penny nails (or larger) to attach the center match to the wales and the top cap to the wales
  • Staples to attach the filter cloth to the center match

The materials list for a wood bulkhead is pretty simple and short. The bulkhead materials listed above will work for most wood bulkheads or retaining walls built around residential locations. If you need a reliable source for wood bulkhead materials, call the people at Building Products Plus in Houston, TX who let me take the pictures above in their yard. They ship nationwide so you can call them from anywhere.

Here’s a simple sketchcast from WoodScience (became Lumber Talk) on how to build a wood bulkhead.

By Chris | November 14, 2007 - 4:16 pm - Posted in Marine Structures, Treated Wood

This sketchcast is an overview of the basic components required to build a pier or dock foundation and how they fit together.


The main components of a dock foundation are:

  1. Pilings
  2. Pile Caps/Beams
  3. Stringers

You will also need the appropriate hardware and surface deck materials for your pier or dock foundation. The sketchcast does not cover spans or what sizes of materials you should use. There are too many variables to even consider putting that here. So, if you want my advice on what sizes to use for your dock foundation I will go for the mega overbuild. Check with your local building codes and consult an engineer to be safe.

Make sure you use properly treated wood when building your pier or dock foundation. For fresh water, use wood treated to at least .60 pcf and use 2.5 pcf for saltwater. Marine environments are really tough on wood foundations.

Along the same vein, use the best hardware you can get. The price difference will be next-to-nothing and you will always know that your dock or pier is really strong. Use hot dipped galvanized or even stainless steel hardware.

If you have any questions about the components, where to get them, or how to build a pier or dock foundation, post a comment here.