Building Confidence

Volume 12 Issue 8
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 framing a wall in a renovation, be sure to add backing at corners, intersections and fixtures. Ref: Remodeling 4: How to Frame a Wall.

And a Bonus Tip:

When removing studs from a bearing wall, be sure to install a header to carry the weight over the opening. Ref: Remodeling 4: How to Frame a Wall.

Ask Dave!

How much concrete do I need for a 6" post 48" deep?

It depends on the diameter of the hole you drop your post into.

Here is a link to our concrete calculator:

Try it out yourself for various diameter holes.

To calculate how much concrete is needed we should subtract the displacement of your 6" x 6" x 48" post which is
0.5' x 0.5' x 4' = 1 cu ft.

Hole Size    Volume of Hole    Concrete Needed
8"              1.4 cu ft          0.4 cu ft
10"              2.2 cu ft          1.2 cu ft
12"              3.1 cu ft          2.1 cu ft

A hole 8" to 10" is good for a 6x6 post.

Our Calculator figures out the number of bags of concrete mix for various weights of bags, as well.


Looking for information on building a dutch interior door.

Hi Rebecca,

I wrote an article on building a door:

It explains backing for the hinges and lockset. If I was making a dutch door from scratch, I would make the entire door, then cut it in half. If you are planning a shelf on the lower half, allow for that. An option is to find a solid door that you could cut down to fit your opening. Watch that the door is not warped.


I am needing to build an arched top set of double doors. It will have a 4" wide frame that is 1 3/8" thick. I'll use dowel joinery. The door opening is 6' wide and 8' tall. The arch portion is 3' high. So there will be two doors approximately 3' x 8', each having half of the arch. I am thinking of using alder for the frame (your thoughts). The panel will be centered in a dado slot in the frame and there will be a flexible 3/4 x 7/16 molding to trim around the edge of the panel on both sides. I need a recommendation for the material to use for the panel. I am thinking a 3/8 thick panel of plywood, or MDF, or hardboard. Would 1/4" thick work or would it be too flimsy? What are your thoughts on the material for the panel?

Hi Martin,

I would try to go with 1/2" plywood - a paint grade hardwood ply, like Birch. This is almost as expensive as G2S fir, but a nicer grain and both sides are good. The frame could be any hardwood, but I would put a cross piece or two to tie the long vertical frame together. With a 1/2" panel, this leaves 7/16" on each side, which is strong enough and the panel should be rigid enough.


Dave I am installing vinyl basement replacement awning windows in a block foundation. The plan is to frame the window in PT (pressure treated) and install the window. Can I cover the PT frame with mortar? If so, what is the best way to adhere the mortar to the PT? Or am I better to trim the PT with PVC. Thanks, Ron

Hi Ron,

I would trim the PT with PVC or with 1x4. I've done this a lot on stucco, as shown in these pics.

Drawing of a typical 1x4 window trim.

Photo of exterior window trim for a house.

Hope this helps,


Feature Article of the Month

(taken from our website:

How to Build a House 4: Install Aluminum or Vinyl Soffits

The Excavation

Our construction dictionary on our website defines a soffit: The underside of elements of a building, such as overhangs, staircases and beams. In this How to Build a House article we will concentrate on the underside of the roof overhang, the eave of the house and the overhang at the slope of the roof, the rake of the house. Generally, there are three ways to frame a soffit, where the rake meets the eave, as shown here:

Drawings of three types of soffit.

Before a house siding job can start, the soffits at the eaves and the rakes of the house should be already installed. The soffit of choice for a house in my area for new construction is the perforated aluminum soffit material. Other choices for a house are perforated vinyl and ventilated wood or equivalent. It is important that... Read more at How to Build a House 4: Install Aluminum or Vinyl Soffits.

Almost the End

Thanks for the emails this month. I hope my answers were helpful to the questioner as well as to our readers.

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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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