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NEWSLETTER
from DaveOsborne.com

Volume 7 Issue 1“Building Confidence”January 2009

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Welcome

Welcome to the building newsletter which strives to build your confidence so you can do it yourself. We hope your winter is a mild one and we can help you plan your projects either at home or work.

What's New!

Dan, my brother and webmaster, and his wife, Marillyn, have opened a drug detox center near Vancouver, Canada. He has been working in this type of field for almost 40 years with excellent results. For more information about their center, please visit their website at http://eaglesanctuary.com/

The very best to you, Dan and Marillyn, in your mission to help others achieve drug-free lives!

Ask Away!

These are the questions that I answered this month.


Dave I have a question for you.
I have a problem. I have a GFI Breaker in my breaker box that runs my
bathroom, now the box says to use ether THQL or THHQL GFCI breaker. Now
this bathroom has a Jacuzzi tub, It runs just fine but when I turn on
the heater for the tub after about 5 mins it pops the breaker. The
breaker is only 15 amp. Any ideas??
 I was thinking of trying just a little higher amp. I do not have any
room in the box to add another breaker or I would run a new line just
for the heater. Also do you have any pictures of the connection points
on the back of theses breakers. The bottom hook part seems to be a bit
hard to find the same one. Now I was thinking of maybe changing the
breaker up to maybe a 20 amp or 30 amp, also figuring that should handle
both the pump motor which never kicks the 15 amp breaker now, plus the
heater which calls for a 15 amp. I think if the pump is off and just the
heater were on which you can not do, but I think it would not kick the
15 amp off, it is just when both have to run it is just too much for that
breaker. But is it safe to go up to a 20 or 30 when there was only a 15
in the box?? Need your advise Cliff

Hi Cliff,

It sounds like you need 2 - 15 amp circuits with breakers.

You can't change the breakers without changing the wire, as well. A 14 wire circuit takes a 15 amp breaker. A 12 wire - 20 amp breaker, etc If the breaker is replaced on a 14 wire circuit the wire could fail and that's exactly what you don't want.

Your option is to put in a sub-panel either near the area of most use or just next to the existing panel. Allow for breakers to be removed in the existing panel to run the sub. This can be done at a nominal charge by a licensed electrician (get quotes) under a permit.

Only buy breakers for the particular brand of panel you have. You can't switch brands of boxes with breakers.

Dave



Dave,
Saw your website regarding carpentry issues and thought I would send you
a question. I am trying to repair a poor install job on the part of the
original home builder concerning an indoor staircase to the upstairs.
The issue involves the very first step that segways to the first landing
and then the staircase begins to the second floor. The first step was
only secured by a piece of 3/8" plywood that attached to the back of the
step. The 2x6 supports are made of non-pressure treated lumber and are
laying against the concrete floor. I want to know if this lumber should
be pressure treated since it is laying against concrete. Also, I plan on
using metal framing plates to secure the step to the framed first level
decking. I can send a couple of pictures if necessary.
Best,
Wayne

Hi Wayne,

The building codes require wood on concrete should be either pressure treated wood (PTW) or laying on roofing asphalt felt. Styrofoam sill gasket is also acceptable, my choice, which comes in 4" and 6" rolls. Be careful in using PTW inside a residence where it is not covered with a finishing material. PTW is poisonous and should be avoided if unprotected and accessible to kids and pets.

Pictures are always good to help explain things.

Dave


Dave,
Have repaired the first stair and am going with your recommendation on
the styrofoam gasket for the boards that sit on the concrete. I have
another issue with an OSB subfloor upstairs. I have all the carpet up
and am in the process of putting screws in all of the decking to stop
any squeaks before re-carpeting. I am using 1 5/8 self taping screws.
Decking is 3/4 OSB. The problem I am having is where the OSB runs
underneath a wall that separates two rooms, I can't stop it from
squeaking. I can pass a thin pieces of paper underneath the supporting
wall 2x4. Can you suggest any solutions, should I possibly use shims or
longer screws. I am open for help.
Wayne

Hi Wayne,

Those screws you are using - self tapping, sounds like screws for metal. If so, their threads are too fine. You should be using deck screws (a flat head wood screw with coarse threads) at least 2" long 2 1/2"x #10 are better. These can be bought in bulk and are quite common. These should be screwed into the joist, of course. The squeaking is probably caused by the ends of the boards rubbing on each other. I assume the sides have a tongue and groove. At the wall you are maybe having trouble getting the joint screwed down if the joist is under the wall. You can try shimming the space above the wall to the OSB. Put a bit of wood glue on the shims to keep them from coming loose over time then cut them flush with the wall line with a utility knife. Sometimes if the ceiling below the floor is not finished, I go below and try to force a latex with silicon caulking up under the joints to stop the squeaking. It's good to try to stop it now before the carpet is laid, though.

Dave



Hi Dave, here's my question (great site by the way). I've built stairs
before and feel pretty confident doing so. But I sometimes have trouble
when building on a big slope. If my deck is on a slope obviously
dropping a tape measure from the deck to the ground won't give me an
accurate rise since the further you go down the hill, the more height
you have to cover. How do you figure out the total rise if not building
stairs over flat land?

This is a good question.

The total rise is the total distance from floor to floor or landing to landing, including any slope involved. This means that you need to figure a rough total rise, then figure a rough total run. Then figure out the extra rise allowed by the slope at the total run position. Here is a drawing that may explain it better.

Dave



Hi Dave,
I stumbled upon your web site while trying to figure out how to build
some cabinet doors for an old cabin kitchen.  The cabin doesn't stay
warm year round (NW Seattle area) so I think about warping.
My dilemma is this, if I buck-up and buy good 1/2" or 3/4" Baltic birch
plywood and just cut out my doors, no real detail, add some hinges after
clear coating the wood, will I get warping? Or am I better off to build
doors with a style and rail?
Thanks
Also, interesting note on your biography, I've been going up to Big Lake
BC for 30 years, and more than once been across that bridge you worked
on, assuming its the one that is there now.
Will

Hi Will,

Plywood would be better than solid wood for less warping. Make sure you seal both sides and the edges. When choosing the plywood, make sure the boards lay flat on the pile. They shouldn't have one corner raised.

Yes, the bridge West of Williams Lake, over the Fraser River, is the same one I worked on in 1960 - my introduction to the construction industry.

Dave



Hi Dave,
Hope you had a good Christmas. We've had more snow than usual,
which is keeping me off the site but making everywhere very
Christmas-card-ish!
Right now, I'm getting into the detailed planning of my main floor
(the one for which you answered the question about OSB v. plywood)
and would appreciate some help with my joists.
The Background
When they pulled down the building I work in (yes, they did give us
time to get out first) I was able to recover the beams from it.
I'm planning to use them as floor joists.
The beams came in two different cross-sections, 4 x 6 and 4 x 8.
To simplify spacing and installation, I'm intending to convert the
4 x 6s into 4 x 8s by fixing 2 x 4s to them.
One end of each joist will rest on a ledge let into the concrete
basement wall. The other end will rest on a log beam. The span between
wall and beam is 12'.
The Questions
As this is the first house I've built (my wife will probably leave me
if it's not also the last), I have a bunch of questions ...

    * Does the idea of building the 4 x 6s up into 4 x 8s make
      sense? Will they be as strong as true 4 x 8s?
    * As I happen to have a stock of 3 1/2" screws, I was going
      to use them to fix the 2 x 4s to the 4 x 6s, staggered, 12" o.c.
    * Is that about right?
    * Should I use longer screws?
    * Should I also use glue, to eliminate creaking?
    * To avoid hitting the screw heads when fixing the subfloor to the
      built-up joists, I was intending to arrange them with the 2 x 4s
      (and hence the screws) on the underside. Any reason not to do that?
    * All the span tables I've come across assume that joists are 2"
      wide. Do you know where I might find span tables for 4" wide joists,
      or is there a mathematical formula I can apply? Given that the
      cross-section and the span are known, I only need to know the
      correct spacing for a given load and acceptable flexion.
    * Do I need to secure the joists to the ledge, or can I just lay
      them "loose" and rely on the blocking, plus the bond between the
      joists and the subfloor, to keep them from shifting?
    * If I do need to secure the joists to the ledge, what's the best
      way of doing it?
    * What precautions should I take to prevent the joist ends that
      rest on the ledge being affected by damp?
    * Where the joists rest on the beam, is it better to butt the ends
      of the joists up against each other, or to let them go past each
      other, overlapping the beam? I have heard of both systems being
      used, and wondered about the advantages/disadvantages of each.

Many thanks in advance.
All the best,
Steve

Hi Steve, how is life in France these days?

Yes, we enjoyed our Christmas very much. We had the privilege to travel with my eldest daughter, Sabrina, her husband, Curtis (Curtis should be familiar to our Newsletter readers as the son-in-law who designed the bike shed, as well as the upper storage above his stairs) and our 3 grandkids in an all wheel drive 7 passenger van to our next Canadian province to the East of us, Alberta, across the Rocky Mountains. We not only enjoyed our Christmas in Cochrane, near the cowboy town of Calgary, with our middle daughter Jacqui, her husband, Mario (to give Mario equal time, he is a pilot with WestJet, Canada's second largest airline, but first with us) and their two kids, but also getting there. It was a 13 hour drive, with stops, through 4 National Parks, a fitting testament to God's creation.

Okay to your letter. Good background info, helps me get the picture.

First of all, let me give you some of my concerns and a little Construction 101. I don't like it when I hear of people using logs particularly for beams. Logs are round and tapered and not the best things for a beam. Make sure the log has a flat section on it, on the top and under the posts and level it accordingly. Also, the logs water content should not be more than 19% or it shrinks too much when drying.

Your 4x8 joists should be good for a 12' span at 16" centers. To strengthen the floor the OSB should be glued to the joists with construction adhesive in tubes, applied with a cauking gun. In the center of the span along the bottom of the joists should be a row of 1x4. This is called strapping and holds the bottom of the joists in place. Bridging between the joists also strengthen the floor unit.

The concrete ledge should have been poured with anchor bolts at least every 64". If not you can install retro bolts (with a steel wedge) that inserts into a hole drilled in the concrete and pounded in with a hammer. A 2x4 is attached to this ledge using these bolts. This ledge should be 4" wide, half the width of the 8" wall, typically. Attach the 2x4, either pressure treated or with a sill gasket under it, flush to the inside of the wall, leaving a 1/2" air gap between it and the concrete. The joists are then nailed to this sill plate. The floor unit being attached to the top of the concrete wall, like this, braces the wall against the backfill on the outside, the slab braces the bottom of the wall, as shown in this drawing.

This drawing shows the typical drop down ledge used on a rancher to lower the number of steps to enter the main floor. In your situation, it probably is different, but the point I am trying to make is the design of the foundation wall being supported laterally by the floor at the top and the slab at the bottom. Does this look anything like your foundation wall?

Okay to your questions, I'll copy and paste them as I go with a simple answer next to each to help you follow.

Does the idea of building the 4 x 6s up into 4 x 8s make sense? Will they be as strong as true 4 x 8s? Yes, and yes, if done properly.

As I happen to have a stock of 3 1/2" screws, I was going to use them to fix the 2 x 4s to the 4 x 6s, staggered, 12" o.c. Is that about right? Should I use longer screws? Should I also use glue, to eliminate creaking? Yes, these are long enough. I would stagger the screws at 6" and use the same construction adhesive as I mentioned above. At the ends pre-drill the 2x4s to prevent splitting.

To avoid hitting the screw heads when fixing the subfloor to the built-up joists, I was intending to arrange them with the 2 x 4s (and hence the screws) on the underside. Any reason not to do that? No, that sounds okay.

All the span tables I've come across assume that joists are 2" wide. Do you know where I might find span tables for 4" wide joists, or is there a mathematical formula I can apply? Given that the cross-section and the span are known, I only need to know the correct spacing for a given load and acceptable flexion. The common Span tables for our dimension lumber in Canada and the US are for 2x- material. The strength of a structural material like a joist, beam or rafter is in the depth rather than the width of the material. I would go with the common 2x8 table to give you an idea. We have this table on our website: http://daveosborne.com/dave/articles/joist-span-table.php The 2x8 row for spruce, pine and fir shows 12'-2" at 16" centers. If you put the 4x8s on 16" centers you are exceeding the code.

Do I need to secure the joists to the ledge, or can I just lay them "loose" and rely on the blocking, plus the bond between the joists and the subfloor, to keep them from shifting? If I do need to secure the joists to the ledge, what's the best way of doing it? What precautions should I take to prevent the joist ends that rest on the ledge being affected by damp? (Explained above while answering an earlier question.)

Where the joists rest on the beam, is it better to butt the ends of the joists up against each other, or to let them go past each other, overlapping the beam? I have heard of both systems being used, and wondered about the advantages/disadvantages of each. Which way I do this depends on the length of the joist. If it isn't long enough to overlap each other, I butt them together and put about a 2' scab over the joint. Regardless, the joists need to be continuous over the span of the floor to ensure the foundation walls are tied together from side to side and end to end as explained above.

Hope this helps,

Dave


We hope you enjoyed our discussion this month and some of it may apply to your project.

Dave

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