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Metal Key Joint
- Thread starter Mike951
- Start date
ConCretin
Well-known member
They make a removable plastic 'cap' that can be removed after placement that provides a void for caulking. Looks better than a crack.
ConCretin
Well-known member
To be honest we don't see the metal keyway used much anymore. Can I ask why you are using it? You might be happier with an alternate method.
The guy who set up my floor for the pour suggested doing it...but no metal cap was put on, so now im wondering if it is commonly left off....
What are the preferred methods of jointing? Is metal keyjoint considered bad?
What are the preferred methods of jointing? Is metal keyjoint considered bad?
ConCretin
Well-known member
A saw cut contraction joint is probably more common. I wouldn't say a saw cut joint is superior but it is simpler and less expensive.
The saw cut joint creates a weak spot intended to induce a crack. If you don't have rebar or mesh you depend on aggregate interlock to keep the adjacent panels flat.
I've seen random cracks right beside saw cut joints that failed to crack. I've also seen sawcut joints in slabs placed on vapor barrier open up so much that they aggregate disengaged and the slab lifted.
The metal form creates a full depth break and forms a key to prevent displacement.
One potential problem with the metal key is the potential for rusting over time. I'd use the removable plastic strip and install caulking to prevent this.
The saw cut joint creates a weak spot intended to induce a crack. If you don't have rebar or mesh you depend on aggregate interlock to keep the adjacent panels flat.
I've seen random cracks right beside saw cut joints that failed to crack. I've also seen sawcut joints in slabs placed on vapor barrier open up so much that they aggregate disengaged and the slab lifted.
The metal form creates a full depth break and forms a key to prevent displacement.
One potential problem with the metal key is the potential for rusting over time. I'd use the removable plastic strip and install caulking to prevent this.