We have a hill in our back yard that had been dug into by the previous owners. We would like to build a retaining wall. The wall will be 20ft. Long and up to 4ft. High. We have done some homework online and have only found examples up to a couple feet high. Is this something that can be done by the average Joe, or should we hire a pro?

What's your skill level and what do you want to build the retaining wall with. Concrete poured. Block wall. Interlocking deco block.

Can help here build big retaining walls all the time.

Post back even if you hire it out. Can't tell you how many concrete or block retaining walls I had to rip out with the backhoe and replace.

We were hoping to uses blocks-12"x7" that slightly taper in the back. We had also done some research on a hidden morder technique and were hoping to do that, in hopes that it would be stronger. We have never done a retaining wall before but we do have some experience in doing a brick patio. And we have a friend that has assisted in building a couple walls. We were just concerned about the hight of the wall and if there was anything more we needed to do to reinforce it and keep it safe.

Thank you,
Sarah

In our jurisdiction, walls over 3' high need to be engineer approved.

What we have done is made two walls each of 2' height, with a two foot garden between them (i.e. a terraced effect) . If you have the space, it can look really nice.

RTW is right on, you can build 2 two foot walls without an engineer. There is certain distance they need to be apart, I want to say 2 feet but could be wrong there. Hard work, a pro would get it done way faster and already have all the equipment.

amricca's gut feel is right - it's 1 foot of horizontal space for every foot of vertical wall. So a 2' wall needs a two foot (minimum) garden. 3' wall needs a 3 foot space etc.

That is a great idea! Thank you everyone. We had not thought about it that way. We were just think about something staight up and down. A terrace look would fit in and look great in the yard with the trees around it. Thanks again.