What is the best foundation watering?

FUN FACTS:  On dry windy days, a great deal of the water sprayed out of sprinkler systems is lost to evaporation.  The loss can be as much as 20%.  Sprinklers are often set to work at night when higher humidity and lower temperatures reduce water loss to evaporation.

Irrigation systems typically do not do a great deal to help foundations.  This may seem odd, but it is true.  Irrigation systems are designed to keep the top 4 to 6 inches of soil damp enough to support grass, annuals, and small shrubs.  They are not designed to get the water deep enough to help a foundation nor are they designed to concentrate water along the edges of a foundation, where it is needed most.

For most homes, the edge of a slab foundation, often called the grade beam, is 24 to 48 inches deep.  (On hillsides and in active soils, grade beams can be as much as 7 feet deep.)  Most of a grade beam is buried in the ground.  If your irrigation system keeps the top 4, or even 12 inches, of soil wet, it will still not be sufficient to completely protect your foundation.

To protect your foundation from settlement caused by expansive soils that dry and shrink, you must concentrate water along the edge of your foundation and apply enough water to keep the soils damp down 4 to 5 feet.  The best way to do foundation watering is by using soaker hoses (which can be linked to a timer and/or an irrigation system).

Soaker hoses should be placed around your foundation.  It helps to bury them a few inches deep, generally 4 to 6 inches from the edge of your foundation.  By burying the soaker hoses, you help to direct the water down and you also help keep the sun from deteriorating your hoses.  Soaker hoses must be used more frequently when it is dry and less often when it is wet.  It is a good idea to reset the timers on your soaker hoses monthly to reflect the weather.

Soaker hoses should not be buried in deep trenches at the bottom of grade beams.  Although such positioning will place water exactly where it is needed, there are real hazards associated with leaks.  A leaking hose, or one that emits water unevenly, can saturate the soils under a grade beam, and adjacent portions of a foundation leading to soils expanding (heaving).  Heaving soils are a serious problem that needs to be avoided.   

The term soaker hose is a generic term that refers to any type of hose that emits water slowly over the length of the hose.  Various types of soaker hoses include:

1. Coarse surfaced rubber hoses that look like they are made of ground-up rubber.  Such hoses allow water to seep out over their entire lengths.  Experience has found several problems.  First, the hoses are easily damaged by sunlight.  If left on the surface where they are exposed to direct sunlight, they seem to break down in as little as two years.  Second, the openings in the hoses through which water seeps are not evenly sized or spaced.  As a result, water might squirt out in one area and seep out slowly in another.   Watering tends to be uneven.  When buried, the hoses are easily penetrated by roots.  There is a real problem with most of the water coming out in half of a hose nearest to the water source.
2. The same type of hose described above, covered in a tube of permeable plastic cloth.  The cloth makes several improvements.  First, although water comes out of the inner hose unevenly, the cloth tube blocks any jets and helps spread the water more evenly.  Second, the cloth tube is more resistant to sunlight, so the hoses last longer.  Finally, the cloth helps to keep roots out of the hoses.  There is still a problem with most of the water coming out of the portion of the hose nearest to the water source.
3. Flat hoses are divided into 3 parallel tubes.  Each tube has small holes through which water squirts out.  One tube has holes in the first third of the hose, the second in the middle third, and the third hose in the last third.  The holes are spaced so that water is emitted evenly along the length of the hose.  Typically, when water squirts out, it does so in jets that spray water up and out four to seven feet.  To be used as a soaker hose, the hoses must be positioned so that the holes point down.
4. Narrow diameter plastic hoses with small openings every 12 to 18 inches.  This type of hose is sometimes connected into grids that are buried under sod or in mulch in a garden.  The hoses are durable, and when properly installed can be used to water broad areas or narrow areas, such as the edge of a foundation.  This type of hose is sometimes referred to as an emitter hose.

The cost range for soaker hoses is from about $.36 per foot to $1.00 per foot.  Emitter hoses, which are the least costly per foot, do require fittings, which adds to the cost.

If you are seeing cracks in your walls, inside or outside, call the professionals at Advanced Foundation Repair.  If you are suffering from seasonal movement that can potentially be addressed by watering, our professionals will let you know.

Watering your foundation during the hot summer months can reduce the potential your building will experience differential settlement for buildings resting on expansive soils.  For the best results it is recommended that you install a dedicated foundation watering system as part of your yard irrigation system which, is run on a schedule, and as part of a complete plan that may also include root barriers and drainage improvements.  It is ideal to have a yard irrigation system, but if you don’t foundation watering can be accomplished by something as simple as an irrigation hose laid around the foundation, connected to a hose bib, with a simple battery powered timer control valve.

There are a few material options for a home-built foundation irrigation system.  In my opinion, for home use, the best and least difficult watering system to install and maintain is a drip irrigation system fabricated from parts you can get from your local box store.  What I like the most about this type of system is that it can be quickly put together to manage a dry soil problem mitigating further foundation settlement and ultimately can be buried as a permanent system to manage foundation care with only a small amount of modification necessary thus providing a quality system.  This is better than the temporary weepy pipe systems that we used to recommend for temporary use that only lasted a few months at most and did not do a good job of watering uniformly around the building.

The inspiration for this article was based upon my own necessity and recent experience.  While I know that foundation performance in Houston often relies on good maintenance and watering, as a consultant I am often too busy to take my own advice.  This was the case this summer at our office south of Houston, but it did provide a good opportunity to show a fast solution that can be migrated into a permanent one.

The first step is to acquire the necessary materials to install a watering system.  Drip irrigation hose is available from your local box store.  While you can get better quality name brand materials from a local supplier, box store materials do work well and are a bit easier to source on short notice, and I was pressed for time.  Most of the hose materials I have looked at include specifications for maximum allowable run for a zone.  You should be sure to start any project collecting such materials for review to base your design.

Prior to buying materials plan out your system layout.  Take measurements around the perimeter of your building so you can limit your maximum runs well under the manufacturer’s recommended maximum hose length to ensure uniform watering, locate water sources, consider how you are going to control watering on a schedule, and be sure to include backflow prevention for safety.  You will need the following as a minimum but use the manufacturer’s specifications and any local codes as a guide.

• Sufficient drip irrigation hose to install 1′-1.5′ from your

  foundation

  and concrete flatwork around the perimeter of your building.
• Coupling to connect sections of the hose where necessary.
• A back flow preventer if you don’t have one on your hose bib or water supply.
• End caps for each zone run to cover the end of the drip hose termination.
• A pressure reducer.  Most drip systems operate at 25

  psi

  and most Houston domestic water supply sources (hose bibs) run around 50

  psi

  -60

  psi

  .
• An adapter to connect to a hose bib or water supply.
• A timer or other method of control.

Start off by creating as simple sketch of the perimeter of your building.  Take measurements of the perimeter and mark them on your sketch.  Mark the location of hose bibs.  Using the manufacturer’s specifications for maximum run break the perimeter of your home into zones with the hose bibs providing a starting point for each zone.  You will want each zone to be less than the maximum allowable run of the irrigation hose, which often is around 200 for drip irrigation hose.  Install a timer and the hose assembly in accordance with the manufacturer’s requirements laying around the perimeter of your home no closer than 1 to 1.5-feet from the edge of the foundation.  Be sure to install a backflow preventer.  For the purpose of getting started and getting some water to the soil you can simply lay the hose on the soil exposed on the surface.  You will eventually want to bury the hose to prevent it from becoming damaged by yard care.  Typically these hoses are buried 6 inches to a foot deep depending upon the potential for damage due to gardening or other activities.

You will need to set a watering schedule for your irrigation system.  We typically recommend watering 2-3 times a day for 10-15 min; however, this varies by location, site conditions, and time of year.  You can find additional information on our foundation watering webpage; however, this will require some testing upon initial setup.  You should also be aware that watering systems are much less effective, or may have unplanned outcomes, under some site conditions such as the existence of large trees or poor drainage.  Consider root barriers and your drainage prior to implementation of a watering system as outlined in our foundation care information.