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Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

(OP)
"The winter is coming" , so I started bringing in the items that are not supposed to stay outside during the cold season. Today I removed some materials that where sitting in the crawl space under the stairs to the basement and to my surprise I discovered the below

Here is a general view of the area with the issues detailed below



It appears that the builder left an opening in the floor slab when they poured the concrete and then it was masked it with a 2x4 and some more cement added in place but not everywhere. The opening goes along the line marked in the schematic representation at the end of the post, it is like a quarter of an inch wide. The white matter that you see there is dust from the drywall that deposited on the floor in that area as the time passed, not sure why.

This is a zoom in for ❶



"The winter is coming" , so I started bringing in the items that are not supposed to stay outside during the cold season. Today I removed some materials that where sitting in the crawl space under the stairs to the basement and to my surprise I discovered the below

Here is a general view of the area with the issues detailed below enter image description here
It appears that the builder left an opening in the floor slab when they poured the concrete and then it was masked it with a 2x4 and some more cement added in place but not everywhere. The opening goes along the line marked in the schematic representation at the end of the post, it is like a quarter of an inch wide. The white matter that you see there is dust from the drywall that deposited on the floor in that area as the time passed, not sure why.

This is a zoom in for ❶ enter image description here

❷ is where you can see that the opening was left there, it is not a crack. It rather seems to be a construction error or defect that was covered up

This is a zoom in for ❸, here you can see that the cover up is cracked



❹ is there just to indicate a spot where you can see that the wood was stained or oiled with something, that is not mold

Here is how it is built. As you can see they put two 2x4 on top of each other. I guess I will have to use adjustable posts to support the floor while I am removing those vertical and horizontal 2x4.

My question is more about the floor, what would be the procedure to clean the place and pour concrete there
Update: I would alos consider suggestions regarding ways to just clean and seal the cavity with some foam or other materials, I do not insist to pour concrete there



RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

That wood sill needs to come out and replace the bottom sill boards with pressure treated dimension lumber. Bare concrete is a sponge and will hold a surprising amount of moisture which then gets passed onto the wood. Wood in contact with concrete will almost always start rotting.

Looking at your sketch-up drawing, that's a load bearing wall. Even more critical that you get this addressed as sooner or later the rotting sill will crush down and your floor will drop. I'd construct a temporary support for the floor beams (properly shimmed and braced), demo the partition wall sill, replace with new wood and fix the floor while you have it open, and then remove temporary floor supports.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

(OP)
Thanks a lot for the advice
What could be the reason for that opening in the floor slab?

It is actually not clear for me how that wood got wet, I think it is evaporating humidity because the wood in other sections of the sill are not rotten at all
The other question that I have is "Should I seal that opening by pouring concrete or anything else?"

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

Floor drain? Hard to tell until you get the wood out of the way. Could be a defect but I wouldn't worry much about the concrete; the bigger concern seems to be the wood sill.

I'd see what the hole looks like before I'd figure out how to tackle it; likely filling it in with a bucket-mixed, non-shrink grout would be simplest and easiest.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

(OP)
Neah ..the drain is somewhere else.

That wall is there just to support the stairs. This is an above the grade windows basement and the main floor is elevated above the ground level.

I am thinking about renting two or three of those HomeDepot adjustable posts and using them to support the beams
I think that demolishing the whole wall is too extreme
What if I just raise the beams for a couple of milimeters so I can extract the two 2x4 that form the sill , clean the area, pour the concrete and then put back new 2x4 (treated wood as you suggested) ?

Thanks
MiniMe

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

I'd say your plan sounds reasonable; I'd consult with a local structural engineer or contractor to make sure you've properly braced and installed the posts and that they have sufficient capacity to support the floor and that the concrete can take the load. It's also good to have someone who can look at the actual site and find any other issues that aren't apparent from the pictures you showed.

I'd agree that carefully removing the 2x4 studs will let you remove the sill, replace the sill, and reinstall the studs. I doubt you'll be able to leave the studs in place and install a new sill.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

(OP)
This thing seems to be localized
I just posted one side of the sill but there is a crack in the concrete on the other side and the concrete formed a small bump on that side
This bump and the crack was painted over and the thing looks stabilized and dry on that side
On the other side the soil or something looking like soil can be seen through that opening and probably the humidity came out through that and condensed on the wood.

Other than that floor is flat and structurally sound and dry and so is the surrounding wall for that space (cinder blocks)

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

Good point; even with PT the sill can still wick up water into the studs. Cheap insurance.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

(OP)
Excellent suggestion, I did not know that I need this.

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

You could probably get away without it given that it's an interior basement wall and you're not worried about sealing or heat transfer. Still, cheap insurance and a good idea if you finish the basement.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

(OP)
It puzzles me when I try to understand why this was left there.
How thick is a standard concrete slab for a basement floor (house built in Toronto around 1960)
I did not stick my finger in that opening to see how deep it goes but I think I was able to see something yellowish like sand with gravel when I held the flashlight about it. I will have a second look tomorrow

Thanks
Mini

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

4 inches (100mm) is typical, a range of 3 inches to 6 inches is acceptable though 3 inches is a little thin for my taste and 6 inches is overkill unless you have vehicle loads.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

(OP)
I posted a related question in the Building engineering forum

http://www.eng-tips.com/viewthread.cfm?qid=416750

I am wondering if this could have anything to do with the main drain of the house

RE: Construction defect in basement slab under stairs in crawl space-do I need to fix this? How?

Hard to tell; it seems too out of the way to be connected. I suspect you'll only figure that out when you get access to it.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries
www.americanconcrete.com

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