Building Confidence

Volume 19 Issue 2
ISSN 1923-7162

Welcome to Dave's Shop Talk's Home Improvement Newsletter of questions from our members on their construction projects, a Tip of the Month and a home remodeling article, both from our website at

Tip of the Month

When fastening Pressure Treated Wood, use the proper special fasteners made especially for PTW. Regular outdoor fasteners will corrode quickly from the treatment used to preserve the wood.

Apply finish to hardwood before grouting ceramic tile that's touching it. This prevents the grout turning the hardwood black.

With oak flooring, don't use a nail set. Use a slotted screwdriver instead, aligned with the grain. These marks, when filled in, will blend better with the grain than a round hole from a nail set.

KEEP BUSY! Now's a good time to catch up on your projects!

Ask Dave!

How do I vent a washing machine without hooking up to a vent stack or through the roof?

You must be asking about a mechanical vent. You can buy these in most hardware stores. They are acceptable by the plumbing code now. Don't hide them in a wall, in case you need to replace it, keep it accessible. Install it above the highest water level of the washer.

Here is a picture of the mechanical vent you need. Install it after the p-trap coming off a tee. Use a 1 1/2" female pipe adapter to screw it into. Use Teflon tape or dope on the threads. They cost under $5.

Photo of an auto trap vent.

Here is more info about the vent at Amazon:

  • ABS construction
  • Use to vent drain lines
  • Helps prevent sewer gas from entering your home
  • Push to connect
  • Spring-loaded to open with negative pressure and close with positive pressure
  • Mechanical Vent installs on the drain line and vents the line without allowing sewer gas to enter the home.
  • For venting sinks, tubs, showers, etc.

Here is an installation picture:

Installation of the auto trap vent.

What is a wet vent? How do you vent tubs and showers?

A wet vent is a vent that is also used as a drain. Maximum trap arm length is 10' for a toilet to the vent, and for a sink and tub or shower the maximum is 5' from the vent.

Diagram of drainage and venting system showing roof, attic, ceiling, vent, sink, tub or shower, drain stack, cleanout, basement or crawlspace and pipe to sewer or septic tank.

The wet vent as shown on the drawing drains the sink as well as acts as a vent for the tub or shower.

The vent off the sink, tub or shower may also return to the main vent as an option to have only one pipe protruding through the roof.

Usually the drain stack is below the toilet and close to it, with a cleanout on the bottom.

Toilet drains are 3", sinks and tubs are 1 1/2" and showers are 2". A tee is allowed for a vent connection but only Y's are allowed for drains.

I want to put down ceramic tile on the kitchen floor. The floor currently has vinyl from the 70's and is flush with my hardwood floors in the dining and living room. My question is do I need to take out the subfloor and replace it so once my tile is laid it will be even with the hardwood?

It is very important when putting in a ceramic tile floor that the floor is stable. The building code requires 1-1/4" of solid wood, above the floor joists. In new construction, we put down two layers of 5/8" tongue and groove plywood. This usually makes the ceramic tile floor higher than the hardwood, so we use a transition strip. In your house check the total height of the sub-floor. You can do this easily by looking at the heating duct cutouts, if you have them. If you have a 1/4" or thicker overlay above the sub-floor, remove it, then replace it with a 5/8" T & G plywood. The maximum height difference, according to the code, is 5/8" between floor finishes.

How does one determine the swing of a door?

Conventionally, a door opens into a room. Stand on the outside of the door facing into the room. If the door swings to the left, it is a left hand door; if it swings to the right, it is a right hand door.

For a door that opens outwards from a room, say for example an outside door or a small bathroom, the bevel on the door is reversed. Also, the lock set hand is reversed. Stand on the outside of the room facing into the room, as before. If the door opens towards you with the hinges on the left, it is a left hand reverse door; if the hinges are on the right, then it is a right hand reverse.


Feature Article of the Month

(taken from our website:

Basics 3: How to Read a Tape Measure

One of the most useful tools in a tradesman's toolbox is the common tape measure. Let's see how to read a tape measure.

The tape measure can be marked with US or English measurements (feet and inches), metric measurements (meters and parts of meters: centimeters, millimeters, etc) or both shared on the same tape. Most tape measures have common elements to be able to use them easily. Most US tape measures have both inches and foot marks. Notice that the 16", 32", 48", 64", etc. are marked differently than the other inch markers. Some tape measures have small black arrows or pointers with a box around the number, other tape measures have these numbers highlighted in red. These numbers refer to the 16" centers for laying out studs and joists. Most carpenters have the 16" centers memorized up to 8', but a little help on the tape measure is well received when you get to 128". As well as the 16" marks, notice a black diamond mark every 19.2 inches, also called the black truss mark. It was put on the tape measure originally to designate the on-center position of residential roof trusses. Rather than placing 6 trusses in 8', every 16", they saved a truss every sheet of plywood by spreading them out. We don't use this position today with our trusses, which are commonly designed for 24 inch centers.

When you read a tape measure a little knowledge of math is needed. We know that 1/2 is the same as 4/8, 8/16, 16/32, etc. We could refer to the 1/2" mark as the 16/32" mark but we usually use the simplest numbers possible. Since we know that 16/32 is 1/2, when looking for 15/32" on the tape measure, for example, it is the first 32nd before the 1/2" mark.

Actually, in the field a carpenter refers to a 32nd as plus or minus a major fraction. For instance, 13/32 is 1/32 less than 14/32 or 7/16, so we say "7/16 minus" and 11/32 is 1/32 more than 10/32 or 5/16, so we say "5/16 plus". This is a fast way of reading the tape measure on the job when taking a measurement of something to cut it to fit. What you should do is memorize the common fractions down to sixteenths.

Here they are:

1/16, 1/8, 3/16, 1/4, 5/16, 3/8, 7/16, 1/2, 9/16, 5/8, 11/16, 3/4, 13/16, 7/8, 15/16 and the inch mark.

How to Read a Tape Measure

Drawing of a ruler showing each fraction of an inch. Notice the size of the graduations on the tape measure changes with the fraction; 1/2 is the largest, then 1/4 and 3/4, then the eighths, sixteenths and the smallest are the thirty-seconds. These divisions are the most common, but you can get a tape measure in tenths and hundredths. I have a framing square that divides an inch into one hundredths.

We use thirty-seconds in the stair calculator, and other instances like that, just for accuracy because when you're cutting 16 stair risers, if you are 1/16th inch out on each stair, you are out a whole inch at the end. Even being 1/32" out gives an error of 1/2"!

Here is a video I made with Dan's help (my brother and webmaster).

Almost the End

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(Ask Dave) (About Dave)

Your source for building tips, woodworking & furniture plans, house plans and building advice directly from Dave...

Hi, I'm Dave Osborne. With over 50 years experience as a journeyman carpenter, foreman and contractor in heavy construction I enjoyed working with apprentices and sharing the tricks of the trade that others shared with me. Now I get emails from Members all over the world and we include many of my answers in our Free Monthly Newsletters. Some of my answers include drawings and instructions specific to a project, but may also answer your questions. I use correct construction terminology, so you can confidently inform your building supply dealers or contractors exactly what you need.


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