Am attaching a window well to the outside foundation wall. Foundation is built with blocks (hollow).

I have some 3/8 x 3" sleeve anchors but considering the block is hollow it made me wonder: is that too long? Would it be better to use a shorter anchor that doesn't extend so far into the hollow part of the block? Or does it not really matter?


1 Answer 1


The expandable portion of the sleeve should always be in the solid part of the block. If it opens partially in the block and in the open void of the block it will hold tightly but if it opens totally in the void, the anchor will side back and forth but still be secure. The walls of the block are probably 1-1/4" thick so depending on the thickness of the window well, get some anchors that expand totally in the block. You have the option of using toggle bolts if you drill into the void also. Avoid using a hammer drill on the block so you don't blow the back of the block off, reducing the thickness you'll need to support the anchor.

  • Thanks for the hint about the toggle bolt. I hadn't seen one of those before. Appreciate your tip.
    – thornomad
    Aug 12, 2021 at 17:15

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