Backer Rod

[dieselgarage]

I was told that I should use backer rod in my control joints prior to filling them.

The issue is my joints are .090-.095 in width. The smallest diameter backer rod I could fine was .250. I tried getting that in the saw cut and that would be a mother to put in 600 ft.

Two questions:

Is using backer rod absolutely necessary?

Do they make backer rod in a smaller diameter than .250.
I have searched and could not find any.

Thanks

 

[PoorOwner]

Why backer rod? Most caulk can fill 1/8" without any issues.

 

[7th Kahuna]

In my experience the backer rod has always been used in larger joints to limit the amount of filler required while at the same time assuring a solid and consistent fill near the surface. If your joints are that tight, I don't see the need. I am assuming this is a flat rather than vertical surface. If the depth of the cut is such that you don't believe you will get a consistent seal, perhaps you could 'back-fill' with a bit of fine silica sand first, brushed out to a relatively consistent depth, and then seal the joints. Just a thought.

 

[EJM02]

Pics help. There may be another approach you can try but hard to tell without seeing the issue.

 

[bigman68]

You should always use backer rod in a joint you are going to caulk. An ideal caulk depth is 1/2 of it's depth with a max of about 1/2" thick. Think of it this way... I will use the rubber band theory... RUbber bands are thin and that let's them stretch, if they were equal on all sides like a chunk of rubber it would not stretch, a control joint is cut in concrete to control where concrete cracks, the caulk put in must stretch as the concrete moves, if it is thin like a rubber band it will stretch and not pull away from the sides of the joint, if you pour it at full depth, like a chunk of rubber it will not stretch, and it pull away from the side of the joint. The smallest backer rod available is 3/8" which is used for your standard saw cut, look in your yellow pages under " Concrete Accessories" you will find supply houses that sell this size, we sell 3/8" up thru 6". Also ask for a Backer Rod Insertion Tool like this:

http://www.albioneng.com/home/produ...d_and_Corner_Model_Backer_Rod_Insertion_Tools

It will make your life way easier for around $50.00.

 

[Stuart in MN]

I was told that I should use backer rod in my control joints prior to filling them.

The issue is my joints are .090-.095 in width.

Thanks

If the joints are that narrow, you don't need backer rod.

 

[dieselgarage]

Thanks for the replies. Give me some new things to consider. I have a roll of .250 backer but with out some serious squeezing and squishing it will not go in the saw cut.

Might have to look into the sand idea.

 

[BlindViper]

I bet you could rig up a jig with a razor blade and either 1/2 or 1/4 the rod u have now.

 

[NUTTSGT]

What are you using to fill the cuts with ?

 

[Always_Thinkin]

You don't need backer rod for control joints only for expansion joints. I deal with this on a large basis with concrete floodwalls and closure structures.