Foam vs Sand - Expansion Joint Filler

[PoolGate]

I am going to finally do my expansion joint after my deck is re-leveled using the expanding foam (jacking) method. I decided on the Sikaflex. I have seen both sand and foam used to pre-fill the void to the proper depth. Are there any advantages of one over the other? Seems like sand would be easier to apply and get level filling all voids.

 

[Bperry]

I am going to finally do my expansion joint after my deck is re-leveled using the expanding foam (jacking) method. I decided on the Sikaflex. I have seen both sand and foam used to pre-fill the void to the proper depth. Are there any advantages of one over the other? Seems like sand would be easier to apply and get level filling all voids.

Sand isn’t compressible which is needed for an expansion joint.

 

[PoolGate]

Sand isn’t compressible which is needed for an expansion joint.

I am referring to just pre-loading the gap as some of mine is over an inch deep. I see both sand and foam being used.

 

[PoolStored]

I have no knowledge of backer vs. sand and what SHOULD be used. Personally, I've had good luck with sand, just make sure the sand is dry.

The bigger issue you may have...if your deck has been sealed, particularly with acrylic sealer, sikaflex will not adhere. Here is an example....

95B543BB-23EC-444C-9C13-282894A94907.jpeg

• PoolStored
• Nov 12, 2022

5AF3E50E-CF6B-4278-9702-6AC9039A373F.jpeg

• PoolStored
• Nov 12, 2022

 

[Bperry]

I am referring to just pre-loading the gap as some of mine is over an inch deep. I see both sand and foam being used.

I know, but preloading the gap with a solid material is in effect the same thing as filling the gap with a solid material. The whole gap needs to be able to compress and expand. Lots of places do things wrong and don’t even add an expansion gap or know why it needs to be there.

 

[PoolGate]

I have no knowledge of backer vs. sand and what SHOULD be used. Personally, I've had good luck with sand, just make sure the sand is dry.

The bigger issue you may have...if your deck has been sealed, particularly with acrylic sealer, sikaflex will not adhere. Here is an example....

95B543BB-23EC-444C-9C13-282894A94907.jpeg

• PoolStored
• Nov 12, 2022

5AF3E50E-CF6B-4278-9702-6AC9039A373F.jpeg

• PoolStored
• Nov 12, 2022

My expansion joint has never been filled with any type of sealant.

I know, but preloading the gap with a solid material is in effect the same thing as filling the gap with a solid material. The whole gap needs to be able to compress and expand. Lots of places do things wrong and don’t even add an expansion gap or know why it needs to be there.

Makes sense. There is a foam strip 5" wide running the entire perimeter of the pool between the coping and the deck. I do see both being done though. I could just fill the entire void with sealant but I would need 4x as much I suspect. Once I get my deck leveled and the expansion joint cleaned out I'll see where I stand. Foam seems to be the most popular but I think sand would be easier to get the void ready for the sealant.

Oh - Part of my expansion joint is vertical up 2 steps. How is that normally done? Masking tape over the top to hold the sealant until it dries?

 

[PoolStored]

My expansion joint has never been filled with any type of sealant.

What I am saying is that if the deck has been sealed, particularly with acrylic sealant, sikaflex will not bond.

 

[PoolGate]

What I am saying is that if the deck has been sealed, particularly with acrylic sealant, sikaflex will not bond.

Nope. Nothing has ever been done it is virgin stone and concrete.

 

[ajw22]

You should be filling the gap with foam backing rod for the sealant to sit on top of. It comes in various widths...

M-D Building Products 20 ft. Gray Foam Backer Rod for Medium Gaps and Joints 71480 - The Home Depot

The M-D Backer Rod provides a base for caulking to prevent caulk waste in deeper, larger gaps or joints. Backer rod can also fill gaps to protect the home against drafts, moisture, dust and insects. Can

www.homedepot.com

 

[Bperry]

My expansion joint has never been filled with any type of sealant.



Makes sense. There is a foam strip 5" wide running the entire perimeter of the pool between the coping and the deck. I do see both being done though. I could just fill the entire void with sealant but I would need 4x as much I suspect. Once I get my deck leveled and the expansion joint cleaned out I'll see where I stand. Foam seems to be the most popular but I think sand would be easier to get the void ready for the sealant.

Oh - Part of my expansion joint is vertical up 2 steps. How is that normally done? Masking tape over the top to hold the sealant until it dries?

Can cut the foam strip down to 4.5” and them seal the top inch with flexible sealant. Or you can press foam backer rod down into the joint and add sealant on top of that.