Category Archives: Foundation

A Healthy Home Part 1a: How Dry is Dry? –


Water in a house, Good Thing, Bad Thing?  Some places like the sink you expect to find water. Other places like the floor, water is a problem. Builders work hard to build a home so water says where it belongs.

RoofLook at the way the roof is installed!  The shingles are layered from bottom to top. They are also lapped over each layer. So water, will drain down the roof and off.  If water gets up under a shingle, the roofing crew has done some other things like roofing felt, metal valleys and flashing to do the job.

Look at the water run off the overhang in the top picture.  When it rains most of the water hits the roof, the overhang changes how much strikes the wall. Matt Risinger, a home builder in Austin, TX, tweeted this graphic recently.


Do you think Matt builds homes with short overhangs?

SidingThe layers on the roof are repeated for the same purpose for other areas of the house. They work the same way. Some are installed the same way, some are installed differently. Other areas of your home have a different experience with water.

Tyvek TopThe outer layer of a wall, the siding, like the shingles, are lapped. The next layer behind the lapped siding is usually known as house wrap. That’s the white covering you see on many new homes, before the siding is installed. Technically, the term for this is ‘Weather Resistant Barrier’ or WRB. Just as the roofing felt helps keep water outside on the roof, the WRB helps keep water outside on walls.

Just as the roofing felt, shingles, and siding are lapped; house wrap should also be lapped, each new layer draining onto the top of the layer below. The directions call for a 6 inch lap, and then tape. The tape is used on house wrap and not roofing felt, because it is a different material, cap nails should be used.

IMG_7672How does the home buyer know the house wrap is right? It passed a code inspection, didn’t it?  This image shows damaged house wrap. Is it taped and lapped correctly? Are the fasteners used according to the manufacturer’s directions.

Do these problems mean that house wrap is bad.  Certainly not!  House wrap is a great product when installed correctly.  It will do the job it is designed to do; act as a Weather Resistant Barrier. It will then, direct water back outside and not allow it into the wall.

DetailWindows and doors need an opening in the wall. These openings must be detailed correctly or water will enter. These details involve flashings, and tapes. How the window is made, with nailing flanges, with foldable nailing flanges or field installed nailing flanges must be considered. Here we see a tape used to seal the nailing flange to the house wrap.

Is house wrap the only type of WRB used?  No!  It is the most widely used in this area. The others will be covered in a future post.

Now if the roof and the wall properly shed water, and they guide any water that gets inside back out, we get to the ground. At this point the water should be directed away from the house.  Gutters and down spouts do a great job when the ground slopes away. Recommended slopes are 1/4 inch per foot for hard surfaces like concrete, and 1/2 inch per foot for other surfaces. Local codes may require more, or a builder preference may result in a larger grade.

damp_proofingThe basement or foundation walls should be damp-proofed on the outside. This is the black spray applied to the concrete. A tile drain system is installed around the exterior of the foundation and tied into a sump to be pumped out of the home.


If these or other equivalent measures are built into a new home, the builder is doing the job right. They are all in the building code. The issue is not what material, the issue is quality of workmanship.

This post is part of a series of posts on A Healthy Home.




A Healthy Home

Healthy HomeBuilding a new home, gives the homebuyer an opportunity to build in all the things they want. The floor plan, bedroom arrangement, windows are all important.

Also right up there is a house that is healthy. Everywhere you look, someone is pitching, this is healthy for you.  We have lots of buzz words for healthy.  Organic, whole grain, anti-oxidant, reduced fat, low sugar, wellness, all-natural are but a few. How do you make a house into a healthy home?  It starts with design and a few simple objectives.   Ideally, a healthy home is:

  • Dry
  • Clean
  • Well Ventilated
  • Combustion by-product free
  • Pest Free
  • Chemical Care
  • Comfortable
  • Safe

read beforeIt seems fairly simple.  We want a roof over our head to keep the elements out.  Hot or cold, rain or snow, we don’t want them in our home.  The dry home starts with a well constructed roof.  That keeps the weather related water like rain or snow out. Then the walls, and the foundation.

Clean may be obvious, or not. Well Ventilated and Combustion by-product free, along with pest free, no toxic chemicals, comfortable and safe seem also to be obvious.  There is a saying about the Devil being in the details.  It is certainly that way in building a home. So a few details on these topics that make up a Healthy Home are important.

I will be posting a series based on the Healthy Home. We will take a look at each of the points listed above and what they mean to the home owner.

Part Ia   How Dry is Dry       Bulk Water from Precipitation

Part 1b  How Dry is Dry       Bulk Water From other Sources

Part 1c  How Dry is Dry       Water Vapor

Part II    The Home Starts Out Clean

Part 3    Well Ventilated

Part 4     Free of Combustion Byproducts

Part 5     Pest Free

Part 6     Chemical Care

The Foundation of your Home: Slabs, Basements, and Crawl Spaces

What is under your home?  I hope you have some solid ground.  If you do great!  Now how did your home builder get to solid ground?

The first of a multi-part topic.
Left: Slab on Grade ready for walls. (courtesy of Wikimedia Commons)

That can be done with a slab on grade construction. It can be done with a basement.  It can be done with a crawl space. A home can use a combination of methods. It is not at all uncommon to see homes with 3 of the 3 approaches.

Above Right: A slab on Grade shows heat loss through the slab. This is under the front door. Inside temperature is 72 degrees, outside is 14 degrees. The cold (blue) pile is snow.

Basements are generally a below ground space that contain living area and is capable of being heated.  This does not include below ground spaces that are for storage or storm shelter. Basements may be full, view out, or walk out types.

Left: Typical craw space, showing rim joist. This has about 30 inches of concrete and a 2×8 floor joist.

Crawl Spaces are below ground space with no living area.  They are generally low head room spaces, hence the name – Crawl Space.  Some you can actually walk in.  I have seen several crawl spaces that are only 12 – 15 inches high, most are 30 – 48 inches high.  Crawl spaces generally have duct work for the HVAC system, plumbing, and wiring. Occasionally the furnace will be in the crawl space.

Below Right: This addition has 2×10 floor joists with support beams. It provides about 8 inches of clearance between the floor and the beam.

Many homes have a basement with crawl space. Builders in one geographical area tend to build with the same approach.  Another geographic area will find another approach being common. In places where the water table is only a few feet below ground you would be hard pressed to find a basement.  In places with large rock formations near the surface, the builder could use any of these approaches depending on how deep the rock is on the building site.  In tornado alley, basements are always welcome for a storm shelter, and some families use their crawl space.

How do these spaces impact the energy use in your home?

Depending on the age of the home, the below ground walls of the house could be of stone, block, rubble fill or concrete.  These are hard materials that have similar physical properties.  They have high thermal capacity; they will stand extended periods below ground in contact with dirt and moisture.

Thermal Capacitance

Thermal Capacitance is the physical characteristic of a material to hold heat. How long does an object stay hot after being heated? The longer is retains heat, means a higher thermal capacitance.

Above Right: The Rim Joist is where the basement window is. Note the heat transfer through this area. It is somewhat diffused by the brick veneer. Outside temperature is 20 degrees, inside temperature is 68 degrees about 10 pm.

Growing up in Southern Nevada, I lived in a house constructed of concrete blocks.  My bedroom was on the east side.  An 8 foot fence stood 4 feet from my bedroom wall. The sun did not shine directly on my bedroom wall until about 11:00 AM and by 1:00 PM it had passed over. I would go to bed at between 10:00 PM or 11:00 PM and the wall would still be well over 100 degrees. So that wall loaded enough heat during that 2 hour period, to still be over 100 degrees 9 hours later. If a material can hold heat like that, then it can also hold the absence of heat, or cold, in the same way. Concrete, and stone have a high thermal capacitance.

Any basement or crawl space wall will extend both above and below ground. It is not uncommon to see a wall 1 and ½ feet above ground and the rest below ground.  If that portion of the wall is un-insulated, the heat will flow through the wall. Heat will flow in during the summer and out during the winter.

The Infrared Image (Above Left) shows a concrete basement wall. The upper part is showing relatively cooler and the bottom relatively warmer. The mid-point of this image is about 4 feet below the top of the concrete wall. The outside temperature is 45 degrees. Imagine the difference at 20 degrees?

What can the homeowner or the builder do to these walls for energy savings?

Insulation is the obvious answer. What kind of insulation is a better question. I would specify the insulation, you choose, to be installed correctly, that it be durable and properly protected from damage.

Before we actually get the insulation, we need to make a stop.  Air movement through and around the insulation will significantly impair the effectiveness of the insulation.  So lets tighten up the area.  The first area to look at is the Rim Joist.

This is on the Rim of the foundation wall. The floor joists, 2×6 or larger or a truss system rests on the top of wall. If you look at any of your rim joist area you will see a number of things.

(Right) An IR image of a Rim Joist. Outside temperature is 70 degrees. This is a south wall and the sun has been shining on it. Lots of solar loading.

Usually your outside faucets come through here. The gas line enters the house at this point, the air conditioning copper tubing, and perhaps other utilities.  I’ve seen dryer vents installed here, and even the flues of conventional hot water heaters.  Those are usually easy to spot because the flue then goes up the side of the house above the roof.  If you have a tankless hot water heater, the PVC flue may well exit the area through the rim joist.  Then you have joints, knot holes and it is not uncommon to see actual holes where something was there and has been removed. All these holes and gaps need to be sealed up.

Remember that insulation does not stop air movement. Caulk is great for stopping air leaks.  You can use caulk straight from the caulking gun.  Some gaps, may need  backer caulk also called rope caulk.  This is ½ inch strands of caulk like material that you can push in by hand. Then come back over it with the caulking gun.  Smooth the caulk with a tool, or your finger to make it go a little farther, make it look a little better and to eliminate any bubbles that might have formed.

If the gap is larger you may wish to use some of the foam in a can. This one part expanding foam uses moisture to cure. Use along a rim joist would probably have enough moisture to cure properly. Take seriously the caution, to not wash with water if you get in on your hands or elsewhere.  Water will cure it.  It will take a couple of weeks to wear off.  If you don’t ask how I know that, I will not turn red in the face!

You can also use rigid foam on larger openings.  Just remember to caulk the edges.  Also remember to caulk the joint between the sill plate and the concrete. New builders use a gasket now,  a bead of caulk is always helpful.

If the rim joist has insulation, you can remove it to do the air sealing.  You can replace it after air sealing, just be sure to install it properly. It is most likely a fiberglass batt, it may have a paper backing on it, it may not.  The paper backing may be facing the inside or the outside. I’ve observed all these in the same house.  The paper backing is a vapor retarder. It should face the warm in winter side of the wall in this area of Kansas.  (Climate Zone 4)  The batt insulation should fill the space between the floor joists, the concrete rim and the subfloor. That space is probably 8 inches deep, 16 – 24 inches wide and 6 ½ to  24 inches high.  Most common would be 8x16x 7.5 inches.

Since the Rim of the foundation wall is usually 8 inches wide, that would allow, at R-3 per inch, insulation of R-24.  I see R-19 batts commonly used here, older insulation jobs or homeowner installed jobs will show R-13, or even R-11.   If you have a ceiling in your basement, you may only have access to part of this area.  You can work in the accessible area and make a difference.

To remove a finished ceiling and then replace after the air sealing and insulation is completing will probably not be cost effective, even if you do not consider the effort of the Do It Yourself labor.

This is the first of a multi-part topic. We will look at Basements, both finished and unfinished, crawl spaces, and slab floors each in more detail.