Ask the Builder: Both poured and concrete block foundations can last … if they’re built right

Q. I’ve been researching foundation types for both new homes and room additions. I’ve narrowed it down to either poured concrete or concrete block. Many websites say poured concrete is better than concrete block. What’s your opinion? Have you worked with both materials? – Carol Ann S., Richmond, Virginia

A. Poured concrete and concrete block are the two foundation types that dominate the residential construction industry here in the USA.

I’ve built buildings using both materials. The last home I built for my family had a giant poured concrete foundation, but in the backyard, I used concrete block to build a magical serpentine retaining wall that looks as good today as the day I built it decades ago.

Here’s the truth. You can build a poured concrete foundation that can crack and cave in within a year, and you can build a concrete block foundation that can last for hundreds of years with no failure whatsoever. Reinforcing steel is what determines success in the battle between the foundation walls and Mother Nature.

If you want a super-strong concrete block foundation, you need to include both horizontal steel reinforcing wire and, in the cores, vertical reinforcing steel that extends up from the concrete footing. The cores of the concrete block need to be filled solid with strong concrete that has small pea-sized aggregate.

Poured concrete foundations also require reinforcing steel if you want the walls to resist the horizontal forces of wet soil. Another key point to remember is that foundation walls buried in the ground are nothing more than retaining walls. They stop the soil from cascading into your basement.

Modern poured concrete foundation forms have revolutionized foundation construction. An experienced foreman with a small team of semi-skilled laborers can set poured concrete foundation forms in the morning, and the concrete can be poured in the afternoon. The next day the forms can be stripped off and carpenters can get to work.

It would take a small army of masons to achieve the same results building with concrete block. Poured concrete is a huge time saver. Be sure you use lots of steel no matter what material you decide to choose.

I’ve created a page at my website that has numerous videos and photos of poured concrete and concrete block foundation installation. Go to: http://go.askthebuilder.com/pouredorblock.