If you’re looking at purchasing a home, or have been in your home for years, this should be a very informative read for you. Obviously every home is different and I will be using some generalizations here, but one thing that is accurate on all homes: Crawlspaces and foundations are probably one of the most overlooked areas of a home.
Let’s take a look at some characteristics of foundations and Crawlspaces through the last 100 years or so in our Puget Sound region. You’ll notice some dramatic differences as building codes have changed over the years…
1900-10s
Generally speaking, modern conventional house framing was developed and widely used by the mid to late 1800’s, but foundations and crawl spaces during this era hadn’t caught up with the advancement of the home’s wood structural elements. Foundations at this time frame could be concrete, but it’s not uncommon to see stone and mortar, piers, and even wood foundations. My experience in these older homes is that many of them have little to no insulation, usually very tight quarters that are often times inaccessible. I have also noticed that the footings, if they were even present, are usually not very deep, and often settling and cracking is noticeable. Many of these homes have exterior crawl space entrances and can really be all over the map with regards to cleanliness under the home.
1920-30s
There aren’t a ton of differences in these homes from the earlier 1900s, but with the popularity of the Sears Craftsman style homes there were more “DIY” homes built during this time than ever before. Many homes were framed on top of very shallow excavations. I have seen entire tree stumps that appeared to be “burned out” to try and kill any growth before the house was built on top of the stump. Typically you’ll see chunks of concrete or rather small precast concrete footings used to support the floor structure. There is still rarely insulation found that was original to these homes and it is common to see active or discarded knob and tube wiring remnants. It would be noteworthy that in some cases the foundations were improving, with some of them having small footings instead of none at all.
1940-50s
This era is where you can see a noticeable difference in the overall quality when it comes to accessibility: rebar being present in the exterior footings and stem wall, and more modern wiring and plumbing elements. Although it’s not entirely true of every home built during this era, the crawl spaces are more frequently present with insulation and larger interior pier pads vs. small chunks of brick, stone, or concrete from years previous. With the introduction of more stringent reinforcement in the late 1940s post-WW2, rebar and more building codes were being implemented when it came to poured concrete foundations. A big improvement for this era of homes!
1960-70s
An extremely popular style of build during this era was the post and beam floor system with no joists. A material that we call “car decking” (really thick 2×6 tongue and groove boards) could span 4’ between beams and depending on the house’s style and size, could have A TON of pier pads. Interestingly so, many homes in this era were ramblers, with not a lot of two story options in the 1960s, so they can have large crawlspaces of 2,000SF+. The foundations continued to improve, but with post and beam, insulation was all but forgotten. I still get into homes in this era that have no insulation at all. Ducting is still usually galvanized sheet metal and is usually missing insulation or very lightly wrapped. It is also very common to see bare wood in contact with dirt or concrete with no preventative measures (specialty materials made for that type of application to prevent rot and insect damage).
1980-90s
As tract home building became even more efficient and production-style, the two story home became much more popular during this era. A return to beams and joists with thinner ¾” subfloor plywood sheets constitute most of the floor systems of this time. Iinsulation (original to the home) is increasingly present and the foundations and footings have more rebar installed in them. With modern building codes being enforced, it increased the vertical space in the crawl to allow for easier access to building components. Although drainage of the footings and property became more commonplace, a draw back from this era is that many concrete steps and patios were poured right up against the home’s siding. The result all but ensured that water intrusion, insects, and rot could be present at these locations. Definitely note worthy.
2000-10s
Even though manufactured I-joists can be found in some homes dating back to the 1970s in our area, they were being used in record amount of home builds during the turn of the century. Many of these products save on resources and have a lot of upsides, but poor installation of hangers, fasteners, or missing adhesives can be detrimental. Energy codes would continue to drive up the efficiency and thickness of the floor insulation, and vapor barriers and water proofing are more common during this time than ever before. Another consideration of this era home is that many seismic straps and brackets were being implemented during the home’s structural design. That sounds great, but with so many details it is not uncommon to see incorrectly installed or mislocated components. Pex plumbing is very common during this time and some copper still too. 9 times out of 10 the crawl space accesses are located on the interior of the home.
2020s-Present
Our present day home construction is hard not to notice: It goes up FAST! Now we see predominately 2 story homes, unless it’s a 55+ community, and ever increasing energy code requirements (as recently as July 1st of 2020). Most homes we go into in this era are I-joists with beams and posts resting on poured concrete pier pads. It is very common to see plastic foundation vents and numerous flashing and waterproofing details around the homes. If you live anywhere within a city limit, typically you’ll see tight lined down spouts that drain into a sewer system or retention pond. This bodes well for our wet climate and keeping the crawlspace dry! The common downside of the rapid pace of home construction is the cleanliness of the crawlspace visqueen. It is common to find debris and garbage tucked under the visqueen, or sometimes just plain as day on top. It is rare to get into a crawlspace today that is not accessible due to shallow grade, and typically they are very tidy too!
Obviously this timeline is very generalized and your home may have unique characteristics or issues that differ from the descriptions above. We are a general contractor with years of experience in construction and are experts in all aspects of the home. We do our best to bring a holistic approach to your foundation and crawlspace needs because your entire house depends on it to perform! Contact us today to set up a consultation!
