I looked at a house today and I have a question about the foundation.
The house is a rancher, 1,800 square feet, built in 1994 with a concrete block foundation/basement. About 5 feet of the the foundation is in the ground and about 3 feet is above ground.
In one corner of the house there are places above ground where the mortar between the blocks is missing. Enough missing that you can see daylight shining though. None of the blocks are cracked. It’s sort of random where the mortar is missing. The longest area of missing mortar is maybe 6 inches long.
If it matters, the house is a foreclosure, the power was off and it’s been empty for a while. There was some water pooling in the basement at the opposite end from the missing mortar, but we’ve had a lot of rain and with no power the sump pump wouldn’t be running.
I’m not sure I’ve ever seen a concrete-block foundation with more than 2-3 feet total depth. Where is this located?
Mortar in a modern brick or block wall should be secondary to its overall integrity; gravity plus reinforcing bars should be providing most of the strength and stability. Mortar is glue and sealer and not terribly strong by itself. So I’d look for correct construction (reinforcing bars, and enough of them) and a lack of shift in the foundation blocks, and a cost for re-mortaring the blocks in place.
This is kind of like a long dent on a car… it could be cosmetic and easily repaired, or indication of deep and lasting damage. You will likely need a pro’s evaluation to be sure.
It will take some inspection to determine the level of the problem. My previous house had a long crack in the concrete block foundation, I had an engineer look at it, he didn’t see it as a serious problem even though water would make it’s way through. He said such cracks were common, just a result of settling, and told me to fill the crack with patch material. The plans showed there was sufficient rebar reinforcement and it never was a problem after that.
You will need to check with a qualified engineer to be sure. It may not be that bad, and it could be a way to bring down the price of the house if you’re really interested in it. I assume it’s owned by a bank now and they may pay the cost to fix it to make the sale.
The foundation/basement on my house (built in 1956) is concrete block and it extends far more than 2-3 feet into the ground, probably around 8 or 9 feet with another 2 feet above.
I guess I have seen deep block foundations, come to think of it. Just strikes me as a poor choice vs. poured concrete for a deep foundation that might intersect the water table. Or are they only used on elevated plots?
My old house was seven feet down. In ye olde days most houses I saw had concrete or cinder block foundations at full depth. Masons worked cheaply in those days and I think poured foundations became the standard more recently. OTOH my current house is at least 75 years old and it has a slip formed concrete basement wall and foundation. It was built by the previous owners family and wouldn’t represent the standard foundation found around here from that time period. There are is a lot of mortared stone in this area in the older homes. No surprise because just digging out the foundation or a basement* would have provided you with the material.
*In Row Dilandese a basement is called a ‘Down Cellar’. Gotta love this weird place.
Sometime in the '80s, in the area of Maryland I grew up in, homebuilders stopped using block and poured concrete. Pre-formed slabs were brought in from off-site; they were 10-ish feet tall, and 6 (?) feet wide. Stood up length-wise (I don’t know how they were fastened together, sorry), then the slab was poured. No idea if they still do this.
As far as the water table:
Our backyard sloped uphill probably 15 feet–that was almost the high point of the neighborhood–and the front yard sloped down 10 feet; the house across the street was level with the road, their backyard sloped down about 40 feet and they were not the low point of the neighborhood. Very few complaints from anyone about flooding in the basements; usually it was a drainage/foundation problem. So not much help re how far down the water table was.
The houses I saw being built with block and mortar when I was young were in Maryland in Montgomery County. It wasn’t until many years later I ever saw poured concrete being used anywhere. I have looked into the price of using pre-cast forms, around here it was more expensive than poured concrete, but that may be because of the limited demand in these parts.
I don’t know how they were originally put in, but when you have them fixed at least you tar the wall, put in weeping tiles and fill around it all with clean rock and a layer of dirt. With the tar, seems just as impermeable as as solid wall.
I’ve actually never seen a basement (here in Ohio) that isn’t concrete block all the way down.
I can offer this: they finally cut the dead-end through at the end of the street about 8 years ago, slapped up some houses and they have the pre-cast forms (they’re also 2 story with garage in a neighborhood that’s mostly ranchers. :rolleyes: ). I have not made as comprehensive a study as I’d like, but I’m not sure I’ve ever seen a poured concrete foundation in these here parts (southern suburban Balto). Is it a New England thing, something to do with the climate, maybe?
Hell, us kids LIVED in that basement. Cool in the summer, not too cold in the winter, throw rugs on the tile floor, couldn’t be better.
In the OP, the house is only 20 years old. Isn’t that pretty unusual for the mortar to be acting up like that so soon?
Older houses around here have block and mortar construction too. When I lived in Pennsylvania in the 70s I mostly saw blocks. Sometime in the 80s after I had left there my brother told me everything was being built with poured concrete to save money. I don’t know what about the climate would make a difference around here, our winters are a little longer, our summers a little shorter, but in these parts the extremes are around the same as you’d see there.
It sounds like poor construction to me. Or maybe it was more than simple settling in the house the OP looked at. I could see repeated cycles of frost lensing in the ground making the blocks separate so the mortar would start falling out, but then the wall wouldn’t have been properly reinforced with rebar. If the mortar has fallen out of horizontal joints the rebar should be exposed. If it’s not there, that would explain a lot.
My concern would be; Why is the mortar missing? Did someone remove it? Did it simply fall out or did it deteriorate due to improper mixing when installed? It may be a minor issue or a clue to a more serious problem.
At the very least, I would have a mason inspect it to determine the cause, cost of repair and also look for possible additional problem areas at the foundation.
We had a house with a block basement in Florida - no really! The lot sloped away and under the back half of the house was a basement with cinderblock walls and a poured concrete floor, built in 2000. We were the first owners, and within the first year, there were cracks in the mortar on one of the walls. It was inspected and all they had to do was point up the mortar (I think that was the term they used) - the wall itself was sound. So it’s possible it’s no big deal.
Then again, we sold that place within 4 years, and it could have fallen down, for all I know… :eek:
Are there settlement cracks visible inside the house, for instance on the walls and ceiling? If so, that’s usually a bad sign… If there aren’t, it may indicate that structural integrity of the house is still intact.
That being said, do you plan to finish the basement? If so, I’ve never met a block foundation that didn’t leak. If not, don’t plan on storing anything on the ground, and be prepared for occasional mop-ups after big storms.
If the blocks are cracked themselves, or have shifted because of the mortar voids, run away. Cracks running along the seams are no big worry; what I described is major league settling with a compromised foundation.
The mortar voids you described indicate the mortar was mixed with too little cement. It was mostly sand, and crumbled away.
