Watching The Trades

Most people in the trades think that caulking is a simple thing. You buy the right caulk for what you want to do. If you want to make small cracks in your indoor wood trim disappear you would use Acrylic Latex. For sealing around the outside of a window you would use a Silicone based caulk. And if you are not overly worried about fumes that it could give off, you can use polyurethane caulk just about anywhere you want to in a standard residential dwelling.

Of course, it is a little more complicated than that. With recent advances in technology, there is a bewildering array of different types of caulk that you could use. But most people who have been around the trades for any length of time have a reasonably good idea of what the trade-offs are. And for those who have not, there are plenty of how-to articles to help you out.

But what most people don’t know is the proper way of applying caulk. Or rather, they don’t understand the proper way of preparing a crack before they caulk it. As a result, most people apply caulk in a manner that significantly reduces its effectiveness.

In order for caulk to perform the way it was designed, it must form a bond with just two sides (i.e it should not bond with the bottom of the crack) and it must not be applied any deeper than half the width of the crack. Failure to keep these principles in mind will lead to premature failure of a caulked joint.

Of course, we don’t get to choose the size or depth of the joints and cracks that we have to caulk. Nor can we make the caulk hover in space until it cures. That is why they make bond breaker tape and backing rod. Both backing rod and bond breaker tape are designed so that caulk will not bond with them. With these you can control both the depth and the width of the caulking job.

This is no great secret. This spec sheet for a polyurethane caulk says….

Install backer rod to set the depth of the sealant. Sealant depth measured at the center point of
the joint width must not exceed joint width and in no case should depth be greater than 1/2 inch
or less than 1/4 inch. Use bond breaker tape to prevent 3-sided adhesion in shallow joints.
Approval of the backer rod or bond breaker shall be made by the engineer.

But even though the spec sheets call for these things, you will almost never see them used in residential work. This is a reflection of the poor quality of work that goes on in most residential work. If you want to know if a contractor really knows his stuff, you would be wise to follow the recommendations of this article and ask the contractor if he uses bond breakers when he caulks.

For further information on this topic, read Success with Caulking by Steve Maxwell.

If you ask an engineer a pipe is vessel and a tube is a structure. The standard measure for a pipe (i.e, the size you use to spec it) is the inside diameter because it is a vessel for transporting gas or liquids. The standard measure for a tube is measured by outside diameter because it is used for structural support.

If you ask a plumber, a pipe is any thick walled tube that can be threaded. A tube is anything that carries gas or liquids and is too thin walled to be threaded. Most plastic pipe is not threaded. However it is thick walled and that is why it is called pipe (You can also get plastic tubing).

In general, a plumber use inside diameter as the standard measures for both pipes and tubing. But Black Iron (and other ferrous metal pipes) and plastic pipes nominal size is only an approximation of the inside diameter. What’s more, the inside diameter will vary by thickness of the pipe wall (which is indicated by the pipe schedule). So a schedule 40 pipe will have an inside diameter that is almost twice as big as a schedule as a schedule 120 pipe even though they are both the same nominal size. To make matters worse, from 14” the nominal size is based on outside diameter.

To make matters even more complicated, the standard measure for annealed copper refrigeration tubing (otherwise known as ACR tubing) is always outside diameter. But this stuff is used by HVAC technicians, not your average plumber.

I don’t understand I why we all can’t be more like engineers. Do we really need a bunch of different standard measures for pipes when they are all used for transporting gas or liquids?

This is a cool idea. If I was in the market for siding, I would look into getting it.

To see the above picture in its original go here.

Concrete staining can produce some beautiful floors as the above photograph can attest. Maineloft produced that floor by using Scofield’s products. But there are many other products out there that you can use. Going by what I have read, all of them seem to produce stunning effects.

All Things Concrete is a good place to start if you are new to staining concrete. The web site has a Spartan feel and information is sparse and to the point. Still, it manages to cover all the basics.

Among other things, All Things Concrete will tell you the difference between an acid based stain and an acrylic stain. This site will also give you basic pointers on how to create basic stain patterns. And last but not least, it has a photo gallery that gives you a realistic idea of what an amateur can accomplish.

If you want a high brow look at stained concrete you can look at Advanced Concrete Enhancement’s stained concrete portfolio. It is a little too geared towards modern art sensibilities for my tastes. Still their work is pretty impressive from a technical standpoint.

In fact, it is well worth checking out all of ACE’s portfolios. They will give you an education on what you can do with concrete.

And just in case the professionalism of ACE shakes your confidence, here is an account with pictures of ordinary people staining their own concrete.

I came across a description of Previous Concrete here. Apparently it is a kind of concrete that is designed to let water pass through. There is picture on the site of someone pouring a glass of water right through a chunk of this concrete. This extreme permeably is necessary as the primary proposes of this type concrete is to reduce runoff.

It is an interesting concept but I have to say that I am suspicious. My first thought was to wonder how it would hold up to the freeze thaw cycle. Here is their explanation…

Freeze-Thaw Resistance. Freeze-thaw resistance depends on the saturation level of the voids in the concrete at the time of freezing. In the field, it appears that the rapid draining characteristics of pervious concrete prevent saturation from occurring. Where substantial moisture and freeze-thaw conditions are anticipated, pervious concrete should be placed on a 6 to 18-in.-thick layer of drainable rock base such as 1-in. crushed stone.

I wonder how extensive the referenced “in the field” experience is?

The answer that I have in a book called Plumbing a House is four wraps. I have seen this rule applied in real life by real people and their work has not leaked. So all is cool right?

Well, the issue is more complicated than that. Some people argue that for the bigger diameter pipes you need to wrap them more times around. If this is true, how many wraps should correspond to what diameter of threaded pipe?

While doing research on this very question I came across information calling into question the four wrap rule. In fact, the most common recommendation on the web seems to be 2 wraps. This comment from a forum is typical……

Many years ago a study was made on a large irrigation system that had numerous leaks. It was found the more leaks were caused by excessive teflon tape, than anything else. Two wraps was deemed adequate. Any more and the fittings were stressed.

Now I was not able to find that study on the net so I have no idea of how accurately this guy is reporting the findings. Nor do I know how rigorous the study was. But many people on the net seem to share his opinion that anything more then two wraps is excessive.

I even came across people who seem to cite the same study that he cited. But nobody seems to want to give the study its proper name. They always just refer to it as a study of an irrigation system. How aggravating.

One of the reasons that I want to see the actual study is that it is my understanding that a lot of agricultural irrigation systems use threaded plastic pipe. It seems to me that the rules for threaded plastic pipe and threaded steel pipe might be considerably different. I can easily see how four wraps of Teflon tape might stress a plastic fitting. I am little more iffy on the concept that four wraps of Teflon is going to stress a 2″ steel fitting designed to handle high pressure steam.

So, should you vary the amount of Teflon you use by the type of joint you are working on? I know one tradesman who argues that you should. Well, maybe argues is too strong of word. He just says that it is something that he does just “to be safe.” He uses the four wrap rule on the smaller diameters but on the bigger diameters he use up to 8 wraps (depending on the size).

But I know better than to go by someone’s “just to be safe” rule. A lot of tradesmen don’t really understand how the materials they are using work, so they just default to the rule that more is better.

Sometimes this rule of thumb works all right. If you are not sure how big your braces should be, err on the side of making them too big. But sometimes more of something can be harmful. So if you don’t know how or why your material works, you don’t really know if more is helpful or harmful.

The problem is that there is some dispute over how and why Teflon tape works. (more…)

From Bob Vila’s blog….

That said, I CAN appreciate a roofing product that claims to last up to 100 years without needing significant maintenance. Such is the case with the steel roofing that Follansbee markets. The secret to their roof’s longevity is a ZT alloy plating over steel. It’s a combination of zinc and tin, and according to the company it can resist the corrosive effects of salt spray for an indefinite amount of time. Why indefinite? The ASTM test to measure the length of time the material can resist salt spray before rusting was abandoned after 5,000+ hours, because the material showed no sign of rust.

This was originally posted at the Ethereal Voice.

I always thought that the reason Sheet Rock screws had so little pull out strength had to do with the type of metal they were made out off. Shows how little I know. Apparently, their weakness has to do with the nature of there thread. From McFeely’s list of Standard Thread Styles…..

Double Lead: Two threads are wrapped around the shank, as illustrated by the blue and red colored threads. One revolution advances the screw 2 pitch lengths advantageous on long screws or in situations requiring rapid assembly. Drywall screws typically use this thread since pull-out strength isn¹t as important as speed. These screws lack the pull-out resistance of “Deep” threaded screws. Typically, #8 and #10 screws 4″ and longer use this thread because of the increased strength afforded by the larger shank diameter.

Needless to say, the whole concept of pitch lengths was new to me as well. This is also from McFeely’s list of Standard Thread Styles….

Pitch is equal to 1 divided by the number of threads per inch. For a screw with 10 threads per inch, one revolution will advance the screw 1/10″ into the wood.