Old rubble foundation wall 1

[poppasonny]

I want to evaluate a basement stone rubble foundation wall for a 250 year old house in New Jersey.

What type of mortar was in typical at that time?

Were footings below the wall typically utilized ?

The wall "looks good" to me.

The mortar appears to be intact.

Although the wall "looks good" is there a more definitive way to conclude that it still has a usefull life ?

Thanks

 

[BigH]

Wow! It might be good to contact an archeologist at a university or even the state archologist - this might be something that he/she would have a handle on - e.g., foundations for wall, type of mortar, etc. Usually they are keen to understand these things themselves. An interesting question - If it has stood the test of 250 years and looks good, I'd bet the chances of its continued good performance subject to no change of use/loadings, etc. would likely be good too - in your likely timeframe.

 

[jdmm]

poppasonny

For younger 100 year old buildings the foundations were typically constructed on a foundation stone that in this area of the pacific north west often consisted of a granite slab. Stone was placed with mortar with close stone on stone contact. For buildings up to 8 stories that I have looked at the foundation walls were often of the order of 2 feet thick. For most of the walls that I have looked at the mortar was generally totally deteriorated but the stone was still in place. Above the ground the builders generally went to double thickness brick.

 

[jjeng2]

I have some experience with these type of foundations and I am in NJ. Generally they do not have footings under them, but they are usually pretty thick, almost as wide as a modern foundation wall footing. As far as I know there is really no way to calculate the strentgth of the wall. The soil pressure can be calulated by simple load and area calcs. Be very wary. I have seen several times where the wall looked solid on the inside of the basement, but when the exterior was excavated the wall literally crumbled. The mortar was essentially sand and Ive described the condition to clients as "nothing more than a pile of rocks". My gut feeling is the walls would be ok if not disturbed, but as soon as you disturb them you run into major problems. I would suggest shoring before excavating. Any new construction should be isolated from the existing foundation and come down on new footings. If the wall has to be disturbed or its loading changed, ideally the affected sections should be replaced. If not, ive suggested pouring a new RC wall on the exterior to essentially encapsulate the wall. Im sure there are some of these that are in good condition but in my experience in Northern NJ, most are in bad shape and it is not possible to accurately calculate their strength.