[carpdad]

My house was built in the 1920s. In nj and at that time this area was the boondocks and the house seems to be diy from the kinds of materials and the workmanship. A craftman built home for himself. A small house just big enough for his family. It's more than a simple cabin, though.

The foundation is, from limited knowledge I have, is a poured concrete. I was drilling into this and all I get is a black dust. The foundation is very soft. Example, I can't get a wall anchor to bite. One of those plastic anchors. Tapcon screw will not bite either. I was able to use hollow wall anchor to get a firm anchor. The anchor that expands as screw is tightened. I think it is called molly bolt.
Anyway, my question is just a general knowledge. What kind of mix was this concrete? What makes the black dust? It is not mold. Dust is definitely drilling dust from inside.

 

[ClarenceBauer]

It could be cinders that came from an old coal fired plant.
The same type of cinders used in the old cinder blocks.

 

[carpdad]

Thank you for the reply. Short search shows similar old cinder mixed poured foundations could be falling apart. https://www.diychatroom.com/f19/poured-cinder-foundation-90645/


I have some little areas, one is about 8" in diameter, that I picked with a hammer because it crumbled but it went in about 2" in a cone shape and became firm again. There was no black dust from here. I got the dust when drilling into it from the bottom of the foundation. I'm in nj so at least no seismic worries. Because of that crumbly area, should I look into the integrity of this foundation? I don't really want to open a can of worms. House, from some records, was built in 1926. As I said, no inspection or such, and high possibility of diy build with cheaper materials.

 

[Old Thomas]

That is where cinder blocks got their name. Many people inappropriately use the name for concrete masonry units (CMU, aka cement blocks).

 

[carpdad]

At least where a small piece of it blew out, makes me think this is a poured foundation. It is parged all over but there is one area where most of the parging fell off and no sign of pieces of blocks. I've decided to live with it and cover it up.:smile: It's been a long time since that area where parging fell and the blow outs are few small spots. I think partly it's the water held in (over several decades) by the front retaining wall with its failed drainage holes.

 

[stadry]

we used to run into those - mostly down in pa - new hope/lambertville area up to easton/phillipsburg but don't recall any in nj,,, those & conc filled clay tile bsmnt walls,,, they're a large pita

 

[carpdad]

In nj, so more than possible that a mason from pa decided to establish here and built his own house. I'm not cutting into this house, so not much chance to come across anything historical. I used to leave my name behind sheetrock and such, having learned from past craftsmen.:smile: First inch chipping into that blow out was very nervous time since failing foundation was a possibility. There is home insurance but not like I could depend on that said insurance, and invasive inspection is not usually allowed around here.

 

[stadry]

where in j ? western part down near delaware river ?

 

[LKent3000]

I have the same issue. 1910 home in Camden County NJ with some foundation issues I would like to rectify. It appears my foundation was also made with locally sourced materials, ie from the local dirt/lake/coal cinders. If I had the spare cash I would get the foundation analyzed to get a proper recipe but if I had spare money I'd also hire a professional .

Does anyone know any companies that can help with historic cements I can use for a proper repair that will not make the problem worse? I want to patch up the parts falling out, I want to clean up some of the skim coat and use a proper product that will let the walls breath, and I want to use an epoxy to repair some vertical cracks. I did speak to an epoxy company that can formulate the product to be more flexible and less rigid.

Attached are some pics. Any help is greatly appreciated!