Lichen and Moss, Green but not always Mean

What’s that green stuff? People, including house inspectors, don’t like to see anything green on house siding, decking or roofing. As we learned last year, even the FHA has a hissy fit over the color green, and will demand eradication, cleaning and painting, even if the green stuff is not damaging anything.
lichen-HouseIn our case, our 35-year-old house’s cedar siding had a few areas with tiny little hairy lichens happily blowing in the breeze along with a few patches of algae. There were no signs of damage after three and a half decades.

But even though the FHA regulations clearly stated that cedar siding was exempt from the rules regarding wood siding, we still had to provide the funds to pressure-wash and stain the house before we could sell it.

The deed was done and the sale went through. We just hope they were careful, as pressure-washing can be much harder on cedar siding than any amount of lichen.

Lichens are a “plantlike” hybrid of fungus and algae that grow all over the world. The self-sufficient stuff can flourish anywhere as long as it gets a little bit of moisture on occasion. It doesn’t retain much of that moisture and it doesn’t take root, making it easy to remove and control. Lichens don’t bother trees and shrubs unless their growth blocks light to the leaves. But people freak out about lichens anyway.

Moss, on the other hand, is a real plant, and even though anything green growing on a roof is often called moss, this is the real bad guy. Mosses are generally found in shady, wet places. That’s why we see mosses in the woods, especially in wetter climates such as western Oregon. We also see them on roofs, decks, and other structures where debris and water can collect and provide a foothold for it to grow and spread. Mosses break down whatever they attach to, providing a surface cover and moist soil environment for other plants. It’s great stuff, but not if it’s chomping on your house or your bridge!
MossyBridge

This is one of our small trail bridges, in sad need of a good cleaning. It is obviously located deep in the woods, and is victim to leaves, fir needles, vines, sticks, and of course, moss.

My spousal unit came up with an easy way to clean the leaves and other debris that collect on all our bridges. A long-handled squeegee for washing windows makes quick work of the task. But alas, this bridge decking has been adopted by moss mostly because of our neglect. For now, we plan to carefully chip the rest of the green stuff away with a knife, as the decking appears to be secure enough for another year or two anyway.

The under-structure is pressure-treated and so far oblivious to the spongy, green, wood sucking plant. Lichen would have been welcome!

MossyBridge2MossyBridge3

 

 

 

 

 

 

 

 

Thanks for stopping by! Be sure to check out our bridge book. It includes some cool ideas that apply to other projects, like how to put a really tall post into a deep hole when you aren’t that tall. Amazon has the book on sale for about $13.00 right now. Here is the link: Building a Small Cable Suspension Bridge with the Cable Locking System
Images, diagrams, and text copyright 2015 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

A Conflict between treated wood and metal parts

Pressure treated wood is a popular product for outdoor construction, i.e. bridges and decks. The chemicals (including chromated copper arsenate – CCA) that were used to treat wood in the U.S. and perhaps other countries were revised in recent years to remove at least some of the potentially harmful properties. The new formulations did help with the environmental risks, but they caused new problems for construction. When wood treated with the new chemicals was exposed to metal parts, the metal tended to corrode, even moreso in water contact environments, in only a few years. The pressure treatments I’m talking about are alkaline copper quaternary (ACQ) and copper azole (CA), which are both active corrosion materials.

So, the experts started recommending using galvanized steel or stainless steel for any metal parts, i.e. connector plates, joist hangars, and fasteners, that came into contact with pressure treated wood. Galvanized steel or stainless steel would withstand the chemicals for a while. So at least, the corrosion rate would be slowed down.

In my experience in remodeling, and specifically rebuilding decks, I found that some structures that had used ACQ or CA showed exactly how corrosive the treatments were. Galvanized steel joist hangers were nearly destroyed in only a few years.

I had this concern in mind when I built my suspension bridge. The cable locking system parts are hot-dip galvanized steel. But I also added a padding-wrap made of a bituminous material to add more protection between them and the painted (another layer of protection) pressure-treated beams that supported the bridge. Maybe I over-did it a little, but I like the things that I build to outlive me.

In building our new house, I ran into the problem again. In Oregon (and I’m guessing other states in the U.S.) it is required to install foundation anchor bolts in the stem wall foundation. These are to tie the house to the foundation. The bolts go through the pressure treated wooden plates and are secured with nuts. I had the issue again of metal making contact with pressure treated wood. I used ungalvanized (standard, but oversized to 5/8″ vs 1/2″ bolts) because I’m not convinced simple galvanization is the answer anyway. I opted to protect the bolts with a sleeve that I made from polyethylene tubing (5/8″ interior) material.

Bolt1

The bolt came through the hole in the pressure treated plate…

Bolt2

and then I used a water impervious roofing material tab…

Bolt3

before adding the galvanized steel plate.

Bolt4

At the completion all metal was completely isolated from the treated wood.

Thanks for stopping by! Be sure to check out our bridge book. Amazon has the book on sale for about $12.00 right now. Here is the link:

Building a Small Cable Suspension Bridge with the Cable Locking System

Images, diagrams, and text copyright 2013-2014 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.