Building Confidence

Volume 13 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

What's New

Be sure to check out our ebooks! We have finished 6 of the 10 eBooks in our Building Confidence series and are being told how helpful they are to do it yourselfers! Let your friends know about them!

Tip of the Month

To install a downspout onto a gutter, drill the appropriate sized hole first and install a thimble.

And a Bonus Tip:

To get rid of the smell of smoke in a house, vinegar works wonders on odors. Setting out small pans reduces odors very well. Another good idea is cotton balls soaked in vanilla extract.

Ask Dave!

Dave, I have an existing set of stairs that is in need of greater support, It has no center stringer. So I want to add a stringer in the middle for greater support. MFD home - stairs going into basement. My total rise is 97 1/4 measuring from underneath the stairs Run of 9 5/16 Rise of 7 5/8 when I put this into the stair calculator I am getting cutout dimensions of Run 9 5/16 Rise 7 15/32 it would seem to match the existing it should be the same as what I measured so the run is the same but the rise measured 7 5/8, vs calculator 7 15/32 is not. What Am I missing here? can you help me out here. I'd like to only do this once. Thanks, you and your brother make a great team. Lee

Hi Lee,

Your total rise is floor level to floor level. It seems that the difference between 13 rises at 7 5/8 and 13 rises at 7 15/32 = 2.03". This may be the way you are measuring the total rise. The stringer should be lower than the thickness of the tread which is cut off the bottom of the stringer. So you need to allow for that in the total rise.

You are duplicating an existing stringer so you need to measure each rise and each run on the existing stringer and duplicate them, even if there is a slight error - duplicate it exactly.

When we layout a stringer we step down the stringer marking the rise and run. You need to step down the new stringer with the exact rise and run of the existing stringer or it won't fit.

Hope this helps,


Hi Dave, I plan to add riser boards to my exterior stairs. How do I account for those using your online calculator? Thanks. Chris

Hi Chris,

You don't have to figure anything in regarding the use of riser boards. They are nailed or screwed on after the stringers are made. You have to allow for the thickness of the tread, by cutting the thickness off the bottom of the stringer, then dropping the stringer down from the upper floor, 1 rise + the thickness of the tread.

I install the stair riser behind the tread. It looks better first of all, but more important is the fact that the riser actually helps support the next higher stair tread. The riser goes behind the lower tread and is nailed to it and fits under the upper tread supporting it as well. The stair risers are nailed onto the stair stringer first, then the treads nailed on after.

Start at the bottom riser, narrower than others, then put on the next riser up. Now nail the first stair tread on the stair stringers and nail the riser onto the tread. Use glue to prevent squeaks. Work your way up the set of steps this way.


Hi Dave, Thanks for getting back to me so quickly. I was confused about what someone else had told about shortening the top tread to compensate for the riser board. However, I now understand that I don't need to worry about that. Thanks for the great explanation on how to install the risers and the treads. Chris

You're welcome, Chris.

It is better to be sure rather than cause a costly error.


Hi Dave, Originally, I planned to build exterior stairs without skirts. I purchased 2x12x16 PT boards for that. Now, I have decided to add skirts to give the stairs a more finished look. Should I be using 2x10x16 boards for the stringers adjacent to the skirts? I'm guessing that may be necessary in order to keep the stair nosing from protruding beyond the skirt. I believe I can and should use 2x12x16 boards for the 2 middle stringers. Does that sound right? Thanks. Chris

Hi Chris,

You caught me just before leaving on a boating vacation. I will be bringing my laptop, but need wifi. When we stop for gas at the marinas is the only time I can connect to email. This is just a warning - don't give up on me, but allow as much as a week to get back to you.

I personally don't like a skirt on an exterior set of steps. I live in a rainy location so a skirt tends to trap water in the corners rather than running off and causes ice build-up in the wintertime.

The size of stringer depends on the slope of the stairs. The minimum is 2x10. The requirement is to have 3 1/2" of wood left under the treads/risers intersection. For a long stringer like 16' go with a 2x12, anyway. You probably need to support the center of the stringers with posts, as well. The skirt inside is usually 1x__, because it goes against the wall. Outside, I would go with 2x__. Yes, the skirt should rise above the nosings so you could go with two 2x8s and a narrow molding to go over the joint, or just go with a 2x12 and lift it up on the stringer a couple of inches.

On exterior stairs, I prefer to overhang the treads over the stringers by 4 1/2" or so, rather than installing a skirt. This cuts down on the span between stringers, too.

Here are some drawings which you may find helpful:

Diagram of stringer support side view of deck stairs and front view of deck framing.

Diagram of deck stairs showing decking, joist, beam, concrete footing, concrete pad or pressure treated wood, stair stringer, handrail with measurements.


Hi Dave Hope you have enjoyed your summer. We are having additional insulation blown into our attic. We use this space for storage and there is also a AC air handler there, so access is necessary. Presently there is loose 5/8 plywood on that areas we need to walk in. What is your recommendation to raise this floor 3 1/2 in?? My plan was to lag and glue 2 x 4 on there side. Thanks Best Regards Ron

Hi Ron,

Our summer has been awesome! We just got home from a boating/fishing trip up the northern coast of BC. We met lots of Americans at the marinas. We stopped at one small marina and we were the only Canadian. Our 27' boat was dwarfed by the large yachts - up to 82'. The Americans were from Colorado, California, etc who leave their boats at Anacortes, WA and travel north from there.

Rather than lag bolts, I would go with long deck screws about 4 1/2".


Hi Dave, I have had my garage for 4 years now and when the contractor poured the floor he came back in a few days and made saw cuts across the floor in 2 directions. This prevented any cracking from migrating, but now I see that on the edges of some cuts the concrete is chunking. Could this be the result of water freezing in the winter and expanding?(not heated) If so, could I clean out and fill these joints with caulking to prevent water penetration? Thanks kindly, Dennis

Hi Dennis,

You are probably correct. It wouldn't hurt, anyway.


Feature Article of the Month

(taken from our website:

Plumbing and Ventilation 3: Questions on Plumbing and Ventilation

Heating Ducts

I am refinishing the basement and need two additional air ducts in the bedroom and bathroom from the existing central air conditioning plenum. I need suggestions and/or diagrams on the proper assembly. I want to use rigid ducting and am looking at possibly 4" or 6" diameter with the total length of both locations of 8 linear feet.    [see answer]

Installing A Shower Valve

Can you tell me how to install a shower valve in my new bathroom. The two 1/2" water pipes are stubbed out between two 2X4's in the wall. I just don't know how to mount the valve between them. Is there some type of special bracket that is made to do this?    [see answer]

Pex Pipe

I see a lot of people using pex for domestic water in new houses. In your opinion what are the advantages and disadvantages of using it.    [see answer]

Plastic Sewer Pipe To Cast Iron Bell

We are renovating an old house that has a septic system. The pipe to the septic is cast iron. How can we change this pipe to plastic pipe?    [see answer]

Pouring A Shower Pan

Do you know about the type of cement to be used for the shower pan?    [see answer]

Range Hood Vent

Where can I find info on installing a rectangular range hood vent?    [see answer]

Toilet Space

How much space for a toilet is normal (the smallest) to have between a vanity and a bath tub?    [see answer]

Washing Machine Vent

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

Wet Vent

What is a wet vent? How do you vent tubs and showers?    [see answer].

Almost the End

Hope you enjoy the Newsletter this month.

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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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