4. Blogs by your San Antonio Home Inspector

Drainage Slope away from Foundation needed

Proper Drainage Slope Is Needed Away From

Your San Antonio Area Foundation

Foundation Drainage Requirements JWK Inspections San Antonio

The illustration above shows proper drainage slope and clearances around the foundation that is needed as per modern standards and minimal IRC requirements. Proper drainage slope based on the International Residential Code is a minimum fall (slope) of 6" away from the foundation for the 1st 10'. Proper clearance above grade to the top of foundation / bottom of exterior cladding is a minimum 4" for masonry areas with a minimum 6" clearance above grade at siding areas.
Proper drainage slope away from a foundation is not just required but needed to help prevent unneeded settling issues to the foundation of a building that can affect the entire structure over time.

The International Residentional Code (IRC) & San Antonio City Code requirements call for proper drainage away from your foundation. Whether the construction is in a cities jurisdiction or not the IRC dictates building codes. City codes whether it's for San Antonio, Boerne, Fair Oaks, Garden Ridge, Schertz, etc are based on the International Residential Code (IRC). But if your not in one of those type AHJ (Authority Having Jurisdiction) areas but out in the county without city (AHJ) review of construction, your builder still has to go by the International Residential Code (the governing body for construction) and also the requirements of the engineers that design the foundation for a new home or any other type building. Engineers will at least require the IRC's minimum but some engineers I've seen even require twice the minimum code based on the IRC. Proper drainage slope is always a requirement for certification of the foundation that the original engineer for the structures foundation had designed on a new home or commercial property construction. Engineers will design a foundation, inspect it before concrete pour & provide certification after approval based on their design & requirements of the foundation. 
Slab Foundation design JWK Inspections San Antonio
Images below are from actual engineers foundation plans for inspections performed by
JWK Inspections that show they require IRC codes for proper drainage but also that
some engineers require twice as much
of the minimum IRC requirements for the proper
drainage away from the foundation and the clearance of foundation above grade.
 
Foundation Grading Drainage Requirements San Antonio JWK InspectionsJWK Inspections foundation pre pour inspection engineers drainage grading requirements
 JWK Inspections Engineers Requirements for proper drauinage slope away from foundationJWK Inspections Drainage grading slope requirements commercial engineer
 Sample Engineers Drainag Slope Requirrement away from foundation JWK InspectionsDrainage slope requirements away from foundation JWK Inspections San Antonio
     The 6 illustrations above are all engineered foundation design notes on the plans by different engineers        
at foundation pre-pour construction phase inspections in the San Antonio or surrounding areas. 3 of the
engineers are calling for more drainage slope then the minimum called for by the IRC. The IRC calls for a  
    minimum 6" fall for the first 10' (5% slope) away from the foundation. 3 of these engineers above are                  
calling for a minimum 6" fall in the first 5', which is 10% slope. Also, 3 of the engineers also call for more
than the minimum IRC requiremnt for foundation clearnce above finished grade. The IRC requires a minimum
4" clearance above grade at masonry areas and 6" clearance above grade at siding areas. 2 of the engineers
call for a minimum 8" clearnce above grade to top of foundation (bottom of cladding) and one engineer shows
a minimum 10" clearance above grade areas. The bottom left illustration shows that engineer calling out,
emphasing no less than 4 times the requiremnt for proper drainage slope away from the foundation and that it
also needs to be established right away, within days after the concrete is poured and forms are removed.  
 

The illustration below shows a Drainage / Grade Level Survey performed by JWK Inspections at a San Antonio area home inspection with the Zip Level System. All the readings were taken at 10' away from the foundation. Requirements call for a minimum 6" fall, slope for that 1st 10' away from the foundation. As seen in the illustration none of the areas met minimum requirements as shown with the documented readings. The red numbers show the inadequate slope in decimal inches. For instance the back left corner has less than an inch slope (fall) with only a 0.8" reading.
JWK Inspection Grading Drainage survey zip level sanantonio

 
  JWK Inspections Drainage Grading Level Survey San Antonio Zip Level Equipment shown at a San Antonio Home Inspection that also included a Grading / Drainage Level Survey by JWK Inspections. Readings were taken at 10' away from the foundation to evaluate needed proper drainage slope as needed as per requirements.

Syndicate content