crawlspace access outside First time home buyers may have heard the word crawlspace (or crawl space) but not had a good idea of what it refers to – especially if they have only lived in houses built on slab foundations. So let’s touch on it today.

What and the Where?

When homes are built on a raised foundation, also called a perimeter foundation, rather than slab foundation, there’s space between the dirt under the house and the house itself – often 3′ (but not always), sometimes more.  Unless the structure is built on a hillside, there won’t be enough height to walk around in that space, hence the need to crawl in the crawlspace.

Most of the time, access to this space is indoors and specifically on the floor of a closet, where there appears to be a flat opening of about 3′ by 3′, sometimes smaller.  This can make entry tight.  At other times. the access is via the outside, as with the photo at the left (more likely the case in properties built before 1950 in Silicon Valley than in newer properties.)

Here it’s a lot easier for homeowners, inspectors and repair people to enter – but also easier for animals and pests, such as rats, to make their way in.  Care must be taken, as with the vent screens, to keep unwanted visitors out!

Crawlspace Video

Auditory learner? Or TLDR, and just want a quick-take? Watch this 1min 46 second video to get the summary:

Monitoring the crawlspace

If your home has a crawlspace, you will want to monitor it.

Red flags in crawlspacePlan either to enter it to check on things periodically or pay an inspector to do so as this is an area which can reveal problems like the presence of termites, water damage to the bathroom floors, damaged heat ducts, cracked water supply or waste lines, and more.

It is also important to periodically check to make sure that there are no intruders (rodents), standing water, or other issues such as cracked foundations.

Which is better – having a crawlspace, or having a slab?

There are pros and cons to each type of foundation. Having a crawlspace makes rewiring, plumbing repairs, and waste line repairs much easier since you don’t have to jackhammer the concrete to get to them.

The newer houses are often built with post-tension slab foundations. Those require special efforts when repairs are needed, and there are warnings stamped into the garages about not jackhammering. That said, they are supposed to be excellent in case of earthquakes.

Houses from pre 1950 or pre 1945 may be on concrete perimeter or raised foundations but without reinforcing bar. Those homes may or may not be bolted to the foundations.

There are many factors to consider and it’s not an easy, black and white answer as to whether or not you will prefer a house with a crawlspace or not.

Not sure if your San Jose area house is on a slab or raised foundation?

Here are some clues as to whether or not the house has a perimeter or raised foundation:

  • If you have to walk up a step or two to enter the house, that points toward raised
  • If the front door is at the same level as the front walkway, that indicates a slab
  • Along the outside of the house, do you see vent screens along the bottom of the house?  If so, the foundation is a raised one. They could be on either the concrete foundation itself or higher up (at the wood or stucco siding).
  • Does the interior of the house have heat registers on the floor? If so, the house enjoys a perimeter or raised foundation.
  • Does the inside of the home have hardwood flooring?  If so, it’s probably on a raised foundation as it’s challenging to put hardwood directly onto slab (you’re more likely to find something like Pergo rather than hardwood on a slab)

Foundation vent

If the home has a crawl space, it’s important to make sure that the access hatch works. Sometimes there’s a handle, but often not, and one of the best things you can do is to add a handle to the top for better accessibility.

If the hatch is outdoors, check it every 6 to 12 months to make sure that there’s no rot or termite damage setting in, that it is sufficiently painted, and that the hatch can still open and close.




Further reading on foundations & crawl spaces

Cracked Foundations, Adobe Clay Soils and Water in Silicon Valley

Historic Homes, Willow Glen, Foundations and Red Flags

What Is Cellulose Debris (in a pest or termite report)?

Wikipedia article explaining what a crawl space is