Crawl space under a basement slab

[randynavarro]

I've never come across a crawl space under a basement slab.

This home was built around 1910.

There was "newer" concrete in the basement but so much storage I really couldn't see how well the concrete was doing.

In one quadrant, the soil had been excavated and a subfloor system had been almost conventionally framed. Then concrete was poured on top of the wood frame system.

The crawl space is not original to the house. The wood framing looks 1950 to 1970-ish.

Here's the hatch cover.

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Here's how the floor framing system was anchored to the adjacent concrete in the rest of the basement.

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Here are the bugs that have chewed the wood plank flooring supporting the concrete. I'm thinking dampwood termites?

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Anybody ever seen something like this? Why was it done?

[mgbinspect]

A definite first for me. Is the slab merely supported by the joists on a ledger that is cut-nailed into the concrete? That's kinda scary...

[Richard Saunders]

I find that crazy and hard to believe! Not the crawl space part, but wearing sandals on a home inspection!

[Marc]

Maybe that's not Randy wearing those sandals.

Marc

[mgbinspect]

Heck, on these 100 degree days here, I definitely wear hiking gear including Keene sandals. Never any negative feedback. And sometimes a bit of envy. Might as well inspect in comfort

[randynavarro]

Note the skin color on the feet. Those feet are not pigment-challenged.

My skin, however, is. Although I am of Mexican descent, I'm almost as caucasion-airy as the next guy.

This inspection was for a 203(k) refinance renovation. Those feet are the homeowner's. In fact, I wouldn't have known or seen that hatch if he hadn't told me about it.

[randynavarro]

A definite first for me. Is the slab merely supported by the joists on a ledger that is cut-nailed into the concrete?

Yes

That's kinda scary...

That's what I thought. However, the concrete above showed no signs of cracking or movement!

[mgbinspect]

It's obviously stood the test of time, but I'd be reluctant to tempt fate by doing the crawlspace inspection while a dance party was happening above.

[Marc]

It's obviously stood the test of time, but I'd be reluctant to tempt fate by doing the crawlspace inspection while a dance party was happening above.

Golly, you're right. I'd join the party!

Marc

[hausdok]

Hi Randy,

What was the soil like in the crawl? Clay? Crawlspaces below basement slabs are used in Colorado a lot because of all of the bentonite there.

ONE TEAM - ONE FIGHT!!!

Mike

[mgbinspect]

Bitte ist was bentonite?

[hausdok]

Man sagt, "was ist," nicht "ist was". Bentonite ist der Bentonit oder der Ton oder "clay" auf Englisch.

Eine Mannschaft - Einer Kampf!!!

Mike

[mgbinspect]

Wirklich dachte ich "was ist" auch. Aber, mein Deutsch ist schlecht - vierzig Jahre alt (fur Lutheran Seminary). Ich mochte Deutsches. Heute erlerne ich Spanish. So, warum bedecken bentonite? - auf englisch fur Randy (I really miss German. It was fun, but I never meet anyone that speaks it so it is impossible to practice.)

Lo ciento, Randy. So, Mike, why would one want to (or need to cover) bentonite?

[John Kogel]

That old rough-cut wood could be older than 1950. It looks like somebody has slammed some new 2X4 support posts under the ledger. Maybe the termites had their way with the old ones.

I wonder if it was originally built as a wooden floor, then covered over later with concrete? Does the site slope down from the conventional floor area to this one? That could explain the why a bit, too much fill required for a slab.

Would the vents have been visible from the outside? That looks like something you would not want to miss in an inspection. You're giving me nightmares now. []

[hausdok]

Hi,

In Colorado the Bentonite expands and contracts so much that it will heave a basement floor. They go deep with a grade beam and pier foundation perimeter and then place a concrete floor above the highest point they expect the Bentonite to heave to during the wet season. They have to leave that area accessible for inspection purposes.

ONE TEAM - ONE FIGHT!!!

Mike

[Richard Moore]

On the insect damage...my first guess would not be dampwood termites. Trouble is I don't know what type of ejected frass would cling to the underside of a board like that. Could it be the remains of an old moisture ant nest that has long since dried up and fallen off?

[randynavarro]

On the insect damage...my first guess would not be dampwood termites. Trouble is I don't know what type of ejected frass would cling to the underside of a board like that. Could it be the remains of an old moisture ant nest that has long since dried up and fallen off?

Yes, dampwood term's was my gut. But, I agree with you, Richard, that clinging frass is interesting.

I guess there's a possiblity there were some sub-termites and their tubes from soil to wood have since fallen, but I truly can't recall ever seeing a full-on soil-to-floor termite tube.

Regardless, as in most finds like this, the type of insect is almost secondary. Getting all the bad wood out of there, period, is my primary recommendation.

[hausdok]

Hi Randy,

Where was this home? If it's anywhere north or east of West Seattle I seriously doubt if it's subs; they don't have travelling papers and visas to come east or north of West Seattle and in 14 years here I've never found them outside of there.

Did you take a piece of that stuff in your fingers and roll it and break it apart? If it was hard and breaks into tiny little mechanical pencil lead sized pellets that look like a little six-sided drum under a lupe then it is DWT frass.

I used to have a little terrarium filled with PDWT, wood mulch and a chunk of rotten wood. DWT are like little brick masons. They'll move out to a part of the nest or entrance to the galleries that they want to block, turn around, eject a pellet, turn around again, smear it with saliva and then pick it up and push it up into the opening. That happens time and again until they've built a solid barrier that will keep other insects - even large carpenter ants - out. Sometimes the frass walls break loose like that and hang off the wood.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

The damage in the third picture wasn't caused by any kind of termite.

I have a suspicion that hasn't been mentioned yet but before I make a fool of myself for suggesting it I need to know what happened to that wood when you smacked it with your pick.

- Jim Katen, Oregon

[hausdok]

The damage in the third picture wasn't caused by any kind of termite.

I have a suspicion that hasn't been mentioned yet but before I make a fool of myself for suggesting it I need to know what happened to that wood when you smacked it with your pick.

- Jim Katen, Oregon

Are you thinking annobiids? If so, I can't recall ever seeing their stuff clump like that and it sure doesn't look like ant frass.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

The damage in the third picture wasn't caused by any kind of termite.

I have a suspicion that hasn't been mentioned yet but before I make a fool of myself for suggesting it I need to know what happened to that wood when you smacked it with your pick.

- Jim Katen, Oregon

Are you thinking annobiids? If so, I can't recall ever seeing their stuff clump like that and it sure doesn't look like ant frass.

ONE TEAM - ONE FIGHT!!!

Mike

Nope & nope.

[randynavarro]

The damage in the third picture wasn't caused by any kind of termite.

I have a suspicion that hasn't been mentioned yet but before I make a fool of myself for suggesting it I need to know what happened to that wood when you smacked it with your pick.

- Jim Katen, Oregon

I didn't whack it for 2 reasons:

1) Clearance at this corner was only about 10". The photo was achieved by sticking my hand under a girder which was about 18" away from that corner and blocked any kind of physical access. I had to also use a bit of zoom.

2) As a 203k renovation inspection, my focus is quite different from an ordinary inspection. The goal is to simply I.D. defects and have them corrected instead of compiling informatoin for them to make an "informed" decision. I outlined two options for the borrower: a) remove and replace all inadequate and damaged wood framing (probably about 80% of what's down there) or b) rip out the framing and concrete, fill and compact with gravel and pour new concrete.

Here are some more photos, Jim, if you want to take a stab at it. . .

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I imagine if I probed, the wood would not necessarily crumble but easily separate. I don't suspect powdery stuff either.

[Jim Katen]

. . . Here are some more photos, Jim, if you want to take a stab at it. . .

Spiders.

- Jim Katen, Oregon

[randynavarro]

Well, that's no so whacky, Jim.

I thought about spiders, but I really don't know much about them.