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Volume 5 Issue 9“Building Confidence”September 2007



Well another month has passed us by, another month closer to Winter. I would still like to get one more fishing day in before the foul weather flies.

What's New

Even with my birthday, this month and our fishing trips I was still able to get out two new plans for the website. One was a custom plan for my son-in-law, a Bike Storage and Utility Shed. The other was a special request from a member of our site who wanted a Child's Bench Seat and Toy Storage Box. Check them out on the website.

Ask Away!

I've been pretty busy this month with questions. I'll share the more interesting ones.

how to vent washing machine without hooking up to vent stack or thru roof

You must be asking about a mechanical vent. You can buy these in most hardware stores. They are not acceptable by the plumbing code, but in a pinch they are good. 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. Here is more info about the vent at Amazon.

Photo of an auto-vent trap.Diagram of drainage and venting system for a bathroom sink, tub or shower and toilet showing how to vent to the roof.


Hi Dave, love your site. I am a small time builder/remodeler, but am
doing pretty well, thanks in a large part to your website.
My question concerns a screened in porch that I want to build at my
lake house. It will be located on a deck off the back of the house.
I rebuilt the deck about 5 years ago. It is roughly 35 x 16, cedar
decking on 2 x 10 x 16 pressure treated joists. I want to screen
about a 16x14 foot area. The support posts for the deck are 8" iron
beams, imbedded in 30" of concrete. The main support beam is a 10"
iron beam, welded to the vertical I beams at about 9 foot spacing.
The deck is attached to the house with a ledger joist bolted to the
house. The main I beam lies at about 12 feet from the house, so the
deck is cantilevered about 4 feet from the main support beam.
I would like to build a three wall screen room off the house, with a
gable roof. My initial thought is to run 6 x 6 cedar posts from the
I beam up to a double 2 x10 header. The 2x10 header would also act as
the plate. I would have to cantilever the 2x10 headers out to the
edge of the deck. I would use 6x6 cedar posts at the four corners.
I would like a cathedral ceiling with 2x8 cedar rafters and a cedar
ridge beam. The roof will be asphalt shingles. By the way, we live in
the midwest, so we could have 15 inches of snow on the roof in rare
instances. The bottom line, after a long-winded dissertation: do you
think I have the basic support system for such an endeavor?
Again, this is a screen porch, no windows, with one door.
I'll appreciate your thoughts. Bob

Hi Bob,

Sorry for the delay in getting back to you, My wife and I were catching a 28 pound salmon on a 2 day fishing trip to the West Coast of Vancouver Island!!

I'm wondering how you got that 10"x35' I beam in place, Wow, a crane, no doubt.

I have a couple of concerns:

  1. Are the 8" I-beam posts sitting on top of a bed of concrete, rather than just concrete embedded on the sides? This is important for an extra load like a roof, etc.
  2. What size ledger and bolts are used on the house which hold up the deck and eventually the porch and roof?
  3. Are the 2x10 joists for the deck at 16" centers?

Usually, when building a house, they limit the cantilever to 16" for a 2x8 joist to a maximum of 2' with 2x10 joists, unless engineered. The code says that for every 1 foot of cantilever the floor joists tails are 6' long.

Your rafters at 2x8 are good, even 2x6 at 2' centers are okay. For the ridge beam, I need to know the state you live in and the nearest large city, to get the wind and snow loads. The double 2x10 headers to support the rafters which have a span of about 15' are too light. I'll give you them when I get the snow loads.

For your info, cedar is not considered a structural wood, such as spruce, pine or the firs. Pine or spruce may be a better choice, with cedar stain applied. Another thing, we use cedar on the inside of a roof like this is to make the large 'fake' beams, etc. from small dimension cedar lumber, if you want that big timber look. That ridge beam is going to be bigger than you think for a 16' span, as well. Also what it is supported on should be looked at.

Thanks for the nice comments, I don't mind the long dissertation, either, it gives me a better feel for what you want to do.


Hi Dave, ditto on the delay getting back to you. I've been at the
lake house all week, re-siding with James Hardie siding and
certainteed trim. No more worries about rot!! I'm using Sherwin
Williams Duration, so this should be my last paint job too.
Now to answer some of your questions:
1. The 8" iron beam posts are embedded in 30 inches of concrete.
But when I installed them, I drilled 2 holes with a 1/2 bit, and
inserted a rebar through the beam, at 12 and 24 inches from
the bottom. Then I filled the 14 inch diameter hole with the concrete.
By the way, when we installed the 10 X 35 foot beam, we lifted it
with 4 of hernias!
2. The ledger is a 2 x 10 with 3/8 in x 5 inch galvanized lag bolts
at 16" spacing.
3. The joists are all 16" centers.

We live in St. Louis, Missouri, and the lake house is located in
Cuba, MO, about 90 miles southwest of STL. So this means we have
thunderstorms with high winds, and some freak snow storms,
ice storms, etc. Throw in the heat and humidity and you just can't
beat the Midwest! By the way, this addition is just a screened room,
not a 3 or 4 season room. I may be over-achieving with this idea,
and am also considering a pre-fab screen room that would just sit
on the deck. My wife just wants a place to get away from the "skeeters"
and to sit if it's raining. I really appreciate any thoughts on the
subject. Again, I love your website! I can't tell you how many times
I have used it successfully. Thanks again, Bob

Hi Bob,

Your snow load is 20 psf with a basic wind speed of 90 mph, not bad!

I wouldn't put anymore weight on the cantilever as possible, especially a snow load. Here is a drawing:

Diagram of how to build a screen room showing ridge beam with measurements.

We have to be careful to observe point loading in a case like this. With the cantilever of the floor joists and the placement of the I-beam at the 12' point, we should support off these points, as shown on the drawing. This way the roof is supported right down to the footings. Wherever you place this room in relation to the deck, make sure the 6x6 posts have support under them. Either the floor joists or install new supports below them to the 35' I-beam. Watch for that.

Your 6x6 posts at the house side should be supported, as well, right to a footing or concrete pad below the deck. The ledger is only for support of the floor not the roof load. On this wall you have the option of putting in a center post to support the 2 - 2x10 ridge beam or tripling up the 2x1o beam, same as the other end. Remember to support the floor under this post, down to a pad on a post.

For the outside cantilever corners try to keep them light with just a standard 2x4 framed corner with sheathing covering the corners and beam for bracing.

Hope this helps,


I live in Charleston, SC and I'm building a 14' x 29' sunroom on the
rear portion of my house. My existing roof is approx. a 5/12 Gable
roof. I need help tying the new gable roof into the existing Gable
roof. I'll purchase the pre-built engineered rafters from a local plant
for the 29' span. However, I need help constructing the rafters for the
hidden valley portion of the sunroom where the new and old roofs meet at
the 90 degree angle. Any suggestion?

Hi Dennis,

If the truss outfit is any good, they can make up a valley set to match the existing pitch of the house roof. If not, I can help you stick frame it.


Thanks for the information. I didn't think to ask the Truss Company if
they would be able to build the valley set for the new roof.

I have an inclinometer to find the exact degree angle of my existing
roof. I want the ridge height of the sunroom to meet the same height as
the existing roof.

Dave, I'd like to have a vaulted ceiling in the sunroom. Do I need to
be concerned with the soundness of the framing if I go with a vaulted
ceiling for a 29 ft. span??? I also want to use the pine 4" tongue and
groove boards for the ceiling material.

I've been putting this project off because I've not had the confidence
to tackle the angles of the hidden valley portion of the new roof. I
poured the 14' X 29' concrete pad over a year ago. I'd like to get this
project started now that the weather is starting to get nice again.

Thanks a bunch for your help!!!

Charleston, SC

Hi Dennis,

Drawing of a scissor truss.A 29' span is a long span for a roof without ceiling joists. Trusses are the best answer. They make a scissor truss for a vaulted ceiling. The bottom chord of the truss is very steep compared to the top chord. Such as in this drawing:

If the truss plant is going to make up the trusses, have the guy come to your house and measure up the pitch and heel height of the existing trusses. He will probably do this anyway.

If you don't go with trusses the rafters will have to have a ridge beam instead of ceiling joists to keep the walls from pushing out during a snow load, etc. More expense and labor. With trusses, the savings on material costs usually offsets the extra cost of material and labor with rafters and ceiling joist or ridge beams.

With any roof plan, the builder is always concerned with the soundness of the framing and building it according to good construction practices.


Hi Dave,

I need to rework and re-contour my courtyard which has existing old
sandstone (poorly fired Mexican bricks) set in a sandy base with an
anemic concrete/sand filler between the old bricks. The patchwork of highs
and lows in the contour distracts from the value of the courtyard. It has
been in place for many years and the shifting earth underneath (no roots)
has taken its toll!

Concurrently, I would like to modify the rain water drainage flow away
from my house and slope it in two separate directions toward the original
fall line/drainage (in front toward the street and in back toward a common
service drive [alley]). The total area involved is probably 900 ft2
along only one side of the house.

How do I set the highest point (elevation) desired and set markers to
use as reference points to modify the drainage line as I reset the old paver
type bricks mentioned above???

Finally, what is the best base to use under the bricks/pavers as I reset
them? (limestone chips, pea gravel ???? And, should I follow with a
mortise slurry mix between the bricks to reduce shifting as they did
many years ago???)

Thank you for your expertise in this matter.


Hi Don,

The high point would be 6" or 8" below the top of your foundation wall on the house and everything will fall from that. Try to work on a 1/4" fall per foot around the house for a distance of 6' or so then you could drop to 1/8" per foot to the street and the alley. If you are familiar with a builders' level this would be my choice of tool. Rental yards have these available, lasers or the old sight through. Every 4' or so drive a 1x2x12" stake in the ground in a line out from the house, at pre-determined distances, for easy figuring. This way you will know the distance from the house elevation and the drop per foot so you can figure out the elevation at each stake. Use the top of each stake as the benchmark. That is, have the person holding the rod or tape measure on top of the stake. Then calculate how far down from the stake the ground should be cut to arrive at the desired elevation at that stake. Write on each stake, with a Jiffy Marker, the distance to cut, measured from the top. Between stakes it is easy to grade the area to get the correct slope.

I'm not used to limestone chips as a base. Here we use either pea gravel or sand. I prefer sand, easy to level and compact. Usually, they don't use a cement grout in patio blocks since the cement would stain the porous blocks. As opposed to a ceramic tile with a hard finish. Just use fine sand brushed into the joints. As long as the base is compacted and smooth the result should be good. There is a plate compactor with a rubber material on the plate, ideal for compacting patio blocks after installation. These should be available at you local rental yards, as well.

Hope this helps,



Thanks for the expertise and effort in the reply! The steps in the
process are clear (even to an old dentist) in the way you presented
them. Now, all I can think about is the sore back and knees in
removal of all of those old bricks - - - gotta find a young helper.
Setting the grade sounds like the easiest part.

Limestone is a common commodity around here and I was told by a
contractor doing other work on the house that it is superior to pea
gravel because the bricks can be maneuvered into place easier where
you cannot really compact pea gravel. I tried sand in a small repair
area - - but after the first rain storm it had almost washed
completely away and the bricks shifted again even after sweeping in
more sand between the bricks/pavers.

FYI: This area of south Texas has significant shifting of soil
associated primarily an endless layer of clay about 12-18" below sandy
loam topsoil.
Changes in rain patterns really provoke swelling and/or contraction of
the clay with associated significant ripples on the surface. It is that
heavy gumbo type clay that a full shovel is about all a good size man
can dig and pitch and then it likes to stick to the shovel.

This keeps concrete contractors and foundation repair firms very busy!
This is why I have decided to replace the old pavers (after contouring)
set in a moldable base (sand, pea gravel or limestone chips) vs. a ridged
alternative = reset the pavers when it gets too bad vs. a jackhammer and
new concrete every 5 years. We just waited too long to simply reset the
pavers this time as it has probably been 18-20 years since they were
originally placed and the sand base has washed away.

Agree with my thinking??

Thanks again!

Yes, makes sense. Pea gravel doesn't compact well, this is true. Rock chips don't settle much, either so that is good. I'm familiar with the Texas rains. My wife is from Midland, so in our visiting I've seen the damage done by the rain and how much comes down in a short space of time. Come to think of it, my father-in-law used to talk about cleechy, which I suspect is the limestone chips, you mentioned.


Hi Dave,

I have a problem with ice dams forming on my roof and water backing
up under the shingles during melting time. I am considering
installing heating cables on the roof where the problem occurs.
Do these things work effectively ????
Thank you in advance for any help.


Hi Jack,

I expect the source of your problem is the roofing along the eaves. Before the shingles are installed a 3' wide or more, layer of 30 pound non-perforated roofing felt is applied to the edge of the roof deck over the eaves. This is required by code, to extend 2' passed the inside wall, up the roof edge. A rubber type of fabric, ice and water shield, is also available. Two other factors to be considered is adequate ventilation of the attic space and the slope of the roof. Shingles should not be installed on a roof less than 3 in 12.

Heating cables on the roof will work, but I would rather get to the source of the problem, ice barrier, ventilation or slope of roof.


Hello Dave
I am pouring a concrete pad on an elevated deck. There is good slope to
the open portion, so the water will run off properly and the sub frame
is strong enough. I'm using 2 layers of torch down which I will lap up
under the siding and over the outer rim board. My problem is that there
is a post which holds up a roof beam that goes right through the middle
of the pour! I'll lap up the torch down a bit but how do i ensure that
the post doesn't rot, and will the pad crack around that spot? Also, how
do you cant strip the house with a conc. pour? Any help would be

Hi Damian,

To prevent the concrete cracking around the post wrap a couple of layers of sill gasket around the post. Sill gasket against the wall, is also a good idea. This will give the concrete some room for expansion and contraction. There is a peel and stick product which would be better than torch on for the walls. Bring the wall tarpaper down to the cant strip and apply the peel and strip to the tarpaper and cant. The cant is installed on top of the concrete, nailed to the wall studs, place the cant on some sill gasket, as well, and trim it off with the front edge. Never put concrete against wood without some protection such as roofing felt or sill gasket, unless the wood is pressure treated.


Hi Dave
Thanx for the quick response!
I have another question in relation to decks.
If one must penetrate an exterior 2x6 wall to support the end of a
2x10 beam for an open, elevated deck. How do you prevent water wicking
along the seams back into the wall cavity? I have been told to space the
3 beam plys with 3/8 cedar shims but I don't like that look. The beam has
slope and will be wrapped with blue skin membrane, so water can't enter
from the top, sides or bottom.

Hi Damian,

I'm not sure what this blue skin membrane is. What you don't want is water getting into a wood frame and not allowed to get out. If this blue membrane is a poly material, I would avoid it. Poly around wood creates moisture rather than keeps it out. I would go with a metal flashing over the beam and wall joint to shed the water away from the joint. Don't wrap the beam, it needs to breathe.

I don't like the idea of shims between the plies of the beam, either. The beam gets its strength from the friction of the three layers against each other and fastened together. We use triple beams all the time, exposed to the weather without any problem, supporting open decks, etc. When the deck joists are supported by a ledger on the house or the outside wall, I always put flashing up the wall and over or under the first piece of decking, to shed water away from the wall.


Well, that is about it for this time, except to inform you to checkout our Member's Photo Page. I had an interesting email from Jaana, this month including her story and pictures. For a look, click on this link:

Dan and I hope you enjoy our website, any suggestions would be appreciated.


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