It is cement block. Usually very heavy, strong, and hard. Even a power driver (even a .27 caliber Hilte) will often fail to penetrate.
I have not seen it on anything built after about WWII, but it may have still been used.
It was popular in the 1920s and 1930s before cinder block made inroads as a cheaper block type.

Hi Tanama.

Congratulations on your cool new old house.

Two of the big advantages that were touted by concrete block manufacturers was that the stuff was cheaper than stone, and--when used as the main construction material in ahouse--that it eliminated the danger of termite & rodent infestation. In my old town, there was whole neighborhood of concrete houses, and after almost a century's worth of algae & moss & general weathering, those houses look just like real stone, or, at least, what real stone would look like if all stones were identical.

Anyway, that's the nice thing about concrete: being compunded from sand & limestone & sometimes a rough aggregate, it eventually takes on the varying colors of natural stone and blends into the landscape. Your foundation has already aquired the nice patina of age, so I wouldn't be in any hurry to blast all that away and recover the dead gray of fresh concrete. That's also why I'd leave the ivy alone. It's historic.

Ivy can play havoc with old brick buildings, but that's genrally because the mortar used with the relatively soft brick is more vulnerable than the hard mortar used with concrete blocks. Good concrete will last just about forever. It's what The Emperor Hadrian used when he rebuilt the Pantheon in Rome--which is still standing almost 1900 years later--and it was what Frank LLoyd Wright used to make his Mayan-Deco 'textile-block' houses in Southern Califnia back in the 192Os.

At any rate, your concrete block is one of the things that contribute to the period character of your house, so be careful before you erase the patina that took decades to develop with a too-aggressive cleaning.

Regards,
MAGNAVERDE.

My whole house is made of that type of block! I'd love to see more pictures of decorative concrete block houses-- don't usually see many of them on these old house forums.

Anyway, I agree, I wouldnt be too agressive with cleaning--doesn't look like there's anything in your pictures that Id be concerned about. You might want to just tuckpoint and repair the cracks. Once you get your wood cleaned, painted and spiffed up any perceived grunginess of the concrete will cease to be an issue.

My house has deposits of black soot (maybe from nearby trains) which I was fretting about for a while but now I'm just letting it be old. Painting the wood porch and window trim etc. helped the overall appearance.

I would remove and try to kill any ivy or vine along the foundation of your house.

It is amazing how much damage vines can cause to construction. Even though I have warned my customers for years about planting vines near the house, I did not take my own advice. I thought I could keep up with the growth and I did for a few years, but I got busy and we lost about 40' of gutter to a very healthy lace vine! Just ripped the gutter right off the house, invaded out soffits and was growing in the attic.

Michele I learned the hard way about ivy also...I never expected one little plant to go onto the 3 story roof. I had some off duty fireman replace a poorly installed skylight and they were the ones who advised me to take it off because it could be a portal for bugs and worse water and therefore ICE. I don't think it bothered the stucco. Tanama do you live in a cold climate? Ice may have been the cause of that crack.. Is that column structural? I would at least want to make sure more water doesn't get in there and freeze...I have limestone front steps (each one is one big piece) and ice caused the bottom one to crack and move in one corner

How’s your house holding up? My house in Florida is constructed with these type blocks. I see them in small towns and cities both in the south and beyond.. I’ll put a picture up next chance I get. I’m visiting family in Louisville right now and there are many applications of those exact blocks here

Oh wow Mario - it took me a while to figure out what was going on in that picture. Very cool! Are you building yourself a new rusticated rockface block house?

I wonder if OP is still around - Im 13 yrs too late (LOL) but I ll say it anyway. I would not powerwash since this old concrete is likely to be very porous and youd drive water into it and thats not good. I used a product called D2L on mine with a plastic scrub brush & then hosed down lightly with garden hose - it did a beautiful job getting rid of algae, mildew and who knows what all that growing on, and INSIDE the block (you coulld smell ithe mildew when weather was wet). Also it was good for just general cleaning of dirt. It looks SOOO much brighter and cleaner. Still old looking, but not so grungy.

You can see in OP's pic the algae growing on the surface. So yeah, I would clean it but dont powerwash and be sure you use an appropriate product for historic masonry that is not too harsh. I followed the cleaning with a clear potassium silicate which solidifies crumbling old masonry. (Limeworks.us was my source for info and products - really great helpful people there, check them out.)

We still make these historically accurate concrete blocks! www.classicrockfaceblock.com

I love that these are still being made! If I was to build a new house I would use these as exterior veneer - they really give a place a unique rustic charm.