How tall can u build retaining wall out 4 x12 block?

depends on kind of block these 4 x 12 block are. assume landscaping blocks since concrete blocks made in 16" lengths.
if these blocks have made retaining walls have lip on side sets on , locks row of block below. if blocks not have lip, not suitable
retaining wall use dirt or soil trying hold push them out of position.
so, use block has lip retaining walls.
stack rows on top of each other lip allow wall stagger area wish retain, gives wall more strength , forms gradual set wall itself.
place clean stone behind wall 12" wide behind wall stack blocks. allow drainage behind wall , keep soil getting heavy , full of water.
have seen these type walls high 8', need remember wall stagger 2-4" each row place. math determine how far wall end height need.

Home & Garden Do It Yourself (DIY) Next