Access to crawl space through masonry stem wall
My small, one-story, wood-framed house will be built on a masonry stem wall three courses (24″) high that will support a raised wood floor. My locale requires continuous rebar along the top course, so the top course will be bond-beam blocks. I need to install an access opening through the stem wall (through the interior floor is not an option), and code requires at least a 16″ x 24″ opening. I can get 16″ of height by leaving out the two bottom courses, but after many hours of searching for an answer, I haven’t been able to learn how I should support the top course of blocks where the bottom courses will be missing. A lintel under the bond beam would take up too much of the barely adequate vertical space of my opening. It would be great if, instead of the bond beam, which eats up 8″ of height across the top of the opening, I could install something that would drop down just far enough at the top of the wall to cover the rebar, which I’m virtually certain I would not be allowed to interrupt across the opening. How might I span the top of the opening without adding to the 8″ of height the top course eats up, or, better, with something that takes up less of the opening’s vertical space?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
Jeff,
You could either (a) get an engineered solution by consulting an engineer, or (b) include another course of blocks.
Thank you, Martin. Sometimes you have to hit just the right phrase in seeking information online. After hours of trying various search phrases that led to countless dead ends, I discovered that "foundation access door" leads me to a product that has a built-in steel lintel and comes in 24x16, 32x16, and other sizes. The 32x16 would take the place of two blocks of width and height in my 24" stem wall. Interestingly, the two biggest home-improvement stores come up empty if you search for "lintel," but they have a very limited selection of these; other retailers have more. The 32x16 runs around $45.
Jeff,
Thanks for sharing that information. Here in Vermont, foundations are rarely built with CMUs; instead, we build poured concrete foundations. That's probably why I was unfamiliar with the product you discovered online. I've learned something.
The products I see online look like uninsulated steel doors -- not a good idea for a sealed, conditioned crawl space. You may need two doors -- a steel door with an integral lintel, and an insulated door with measurable R-value and weatherstripping.
Jeff,
Your description of the crawlspace leaves me with a few of questions (which you have probably already thought through).
- If the opening is the full height of the foundation walls, extending right down to the footing, how do you run your perimeter drains and keep water from infiltrating the opening?
- Is there no backfill against the house?
- What height is the slab inside the crawlspace? How does this work with the door?
Thank you, Malcolm, for helping me make sure I haven't overlooked something, which is never too unlikely.
I will build a covered well around the access door, much like one of these:
https://www.customcoversinc.com/pages.php?pageid=8#Crawlspace%20Well%20Covers
It will hold the 6" backfill out of the way and keep what little rain we get here in the desert away from the access door. The door opens outward and downward, so nothing inside the crawl space will get in its way.
Thank you for the caution about insulating the door area, Martin. My desert climate is one where, from what I've read here and elsewhere, a vented crawlspace can work well, especially with polyiso sealing the undersides of my floor joists, even though it will be fairly tedious to install.