I have contractor company building a retaining wall for me which is 6 feet tall wall. They don't install fence.

So I have the cap glued down properly and secured. Can I get the railing install on top of the cap. the railing will be bolted to cap.?

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  • railing for what
    – Traveler
    Commented Aug 26, 2022 at 20:36
  • To prevent kids falling from. also its code that you have to have railing for more than 3 feet tall wall.
    – PowerTech
    Commented Aug 26, 2022 at 20:44
  • 3
    Would be concern about the cap being strong enough and secured enough to hold the railing if a kid bangs into it. To just hold the railing up and look nice should not be a problem. Can you get the railing people and the retaining wall people to talk to each other.
    – crip659
    Commented Aug 26, 2022 at 22:01

2 Answers 2


I recommend you use six-foot (72 inch) posts inserted about halfway into the wall. The tops of the posts, or the top of the railing they will support, should be 39 inches above the grade of the gravel behind the wall.

The wall blocks seem to be hollow, and filled with gravel. So you could insert the posts into the blocks as the wall is built and tamp gravel around them.

A stronger construction is to bury the posts' lower halves just behind the wall. This loses about 6 inches of real estate but minimizes chances of cracking the blocks.

Of course you should have planned the railing and installed the uprights as the wall was being built. Your contractor is not going to like digging up gravel and tamping it down again.


The answer is no.

You cannot fasten an aluminum railing to your glued down wall caps and expect it to be strong enough.

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