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Question DetailsAsked on 3/22/2014

how to replace expansion joint material in concrete

old expansion joint material in concrete flatwork (outbuilding) is gone - how do i replace it/with what do i replace it?

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2 Answers


Expansion joint materials are usually readily available at most lumber supply store such as Lowes or Home depot .

The product is typically removed from the joint by using a small crow bar , screwdriver or even an ice pick . Be careful Not to xxxx or cut yourself.

Installing the new expansion joint material is , in Theory , not difficult . Now this is where theory and practicality meet the road , because sometimes the material is sightly larger than the existing joint .

In theory , You should be able to merely insert the new material into the slot of the joint, but often , it does not work so easily ,and you force or using subtile pressure make the joint material slide into the existing joint cavity. It is also reccomended that you can place a 2x4 or 1x4 block of the same lenght as the joint material and using a 16oz hammer , gently tap the material into place .

Do NOT beat the daylights out of the joint material , as it Will deform and become useless !

Answered 5 years ago by BentheBuilder


The old expansion joint materials was probably asphalt impregnated fiberboard or maybe an elastomeric strip - designed to provide a total bond break between the slab pieces when cast and provide room for later expansion. While I guess it is possible to replace it with the same if the joint is wider than the board, that is not really what you want now because it does not keep water and dirt out - you want a joint sealer now, which is harder to do when pouring concrete so except on critical structures like dams the fiberboard is used.

A couple of solutions, especially since this sounds like a semi-indoor application, where the first two will give long life but only last 3-7 years outdoors:

1) standard bulb type foam caulk backer rod in correct size to compress into joint (if deep), topped by concrete caulk - instructions for using backer rod on package. Look like this, rod comes in various sizes - caulk can be latex (not weatherproof), acrylic, or polyurethane self-levelling - comes in contractor size tubes and tubs too for larger jobs

2) expand in place urethane joint sealer, which you then trim off flat with a putty or drywall knife or paint stripping blade on a grinder after it has expanded and cured -

3) an asphaltic crack sealer, like this, coated with sand after application to make surface non-sticky - this is actually an asphalt repair product, but works great in concrete as long as joint is cleaned and washed first - ends up black of course but does take paint once cured. You mask the joint with duct tape, then melt into the joint, then immediately strip of duct tape, and carefully clean up any overlap on the flat with paint thinner or brake cleaner. Needs sand or cement dust sprinkled over top and walked in (under saran wrap) after placement to keep from being sticky on shoes. Better for outdoors.

4) to remove old joint board or caulk, I use a skil saw with an old nail cutting cutoff blade for bulk removal, then abrasive cutoff blade to clean to the edges, followed with a sawzall with a grout removal blade for final cleanup of any small pieces or tight places if needed, then pressure wash, or for indoors shop vac followed by brush and sponge wash with water and shop vac. A 4 inch cutoff tool or disc grinder with abrasive blades would probably work too for small areas, but for large areas you would get hand cramps like nothing else. For large jobs there is a special chain saw blade that works really swift. Just a sawzall with grout removal tool would probably work for small lengths too, as would any sharp hook type tool like a cotter pin removal tool or 90 degree bent flat screwdriver sharpened to an edge. If you are in a place where splashing water is not a problem and have a 2000 psi or higher pressure washer that will take it right out with a jet tip, but be careful not to erode out the fill material under the joint that way.

Answered 5 years ago by LCD

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