Are concrete expansion strips needed?

[Eileen]

We just installed three patios and a set of stairs connected to our current patio. My husband noticed they did not install expansion strips. He questioned it, and this is their reply. My question: are they telling us truth, or trying to avoid rework? "In reference to the concrete, we did dowel into the concrete as requested. However we did not provide expansion strips due to the fact the point of an expansion strip is to allow the concrete to remain free standing from the foundation. Therefore by doweling into the foundation, this would defeat the purpose of providing an expansion joint. Consequently the expansion joint would only create an eye sore to the patio and more importantly provide a point of entry for water, which in our experience has created problems. Expansion joints have allowed water to enter beneath the concrete and in between the foundation, which after a season in Colorado of freezing and thawing will inevitably cause problems. It is our policy not to use expansion strips due the problems we've experienced after using them. Also, the only concrete typically inspected in a county are areas for structural purposes. "

[Lawrence]

Considering their detailed explanation they gave you it hardly matters what the facts are. They are not coming back to put in any expansion joints regardless of anyone may say. I'm not expert in this field but the sidwalks I have seen all have expansion cracks. No concrete sidewalk last forever and all of them eventually have some type of cracks whether or not they are doweled and whether or not they have expansion joints.

[Art]

Interesting site:

I think you should have joints sawed.

[Art]

Without seeing your job it is hard to know where you might need expansion joints but it might be a good idea not to have them next to the house but that doesn't mean you shouldn't have them. Also concrete passes water pretty readily even without a joint.

[scott21230]

I agree. We would need a picture or diagram with measurements to be more sure.

[Big_Jake]

Art, you and Lawrence both seem to be thinking of the joints that allow concrete to crack due to shrinkage. These can be tooled in the surface or saw cut. The OP is talking about the expansion felt or foam that you would put along a building, retaining wall, or other slab that you would want the new concrete to move independently of. Two totally different things.

JK

[DanG]

The reason for using expansion joint(s) is to give the concrete a place to expand when it is trapped and when the pavement sections get long and need relief to grow in summer heat. A sidewalk trapped between the foundation and the driveway, between two buildings, between the garage and the street are all examples of places that need expansion joint, they are also placed about every

60 feet in sidewalks and paving. Expansion joints are installed before the concrete is poured, they are not typically something to install after the fact, and the results would likely not be satisfactory .

Contraction joints are sawed or tooled to T/4 depth.and designed to give the concrete a controlled place at which to crack. Concrete will crack and should not ever exceed 12' in any one direction without a contraction joint. Re-entrant corners require joint relief as do substantial dimension changes.

It sounds to me that you had a fairly professional crew pour your concrete and I don't disagree with anything they said. I do assume you have sufficient contraction joints, I assume your patio(s) touch grass on 2 or more sides so the concrete is not trapped. I assume you have sufficient grade, 1/4" per foot, to get water off the slab and away from the house. ______________________________ Keep the whole world singing . . . . DanG (remove the sevens) [e-mail]

[Italian Mason]

Hi, As DanG explained the proper use of expansion joints this was a proper install for your application. It sounds like they did a good job, heck you are extra lucky they even knew to dowel in..and why.... there are so many guys that think since they have a truck and a bucket of finishing tools that they are concrete contractors. Seriously you were lucky be happy with the results and recommend these guys thats what keeps us good guys one step ahead of the rest.

[nospambob]

[Susie]

The felt strips that were put in 26 years ago have withered away. Is it a good idea to install new strips to keep water from going under drive and garage concrete?

[Don Y]

A lot of that depends on where you are located and the conditions you are likely to encounter.

E.g., water migrating under there can lead to frost heave in the winter time (if you experience significant cold in Winter)

Why would you *not* want to undertake this? As a lazy solution, you might be able to try silicone (sp?) caulk -- but, you'll use a boatload of it!

[If you go that route, consider rolling up (loosely) some news paper and jamming it in the slot to fill up some of the void so you don't end up pumping "gallons" of caulk into a slot that extends down several inches, etc.]

As an aside, note that this slot is an excellent way to get cables (e.g., landscape lighting, irrigation, etc.) across a driveway without having to use a water drill to bore *under* the slab! Sort of like wedging speaker cables, phone lines along the edge of wall-to-wall carpeting inside your home!

[Susie]

My husband says they are used as a buffer between garage floor and drive when they are poured. Would you explain to him now that they have deteriorated when can happen to the concrete drive and garage floor?

[Don Y]

Concrete can expand/contract with temperature. We frequently see sidewalks "buckled" here -- not from roots or anything beneath but, rather, from the cumulative effects of prolonged heat and undersized/missing expansion joints.

Water can also infiltrate under the slab and heave (when frozen) during the cold months.

You can fill the joints with a caulking compound, buy more "felt" or other products designed for "expansion joints". It's hard to guess what problems would befall you without knowing what sort of conditions you are likely to face.

With most of these things, if it's there, it's there for a *reason*!

[Susie]

I live in Ohio and have had the harshest winters these past two years. If he doesn't fill the void between the drive and the garage floors, is it likely that water will undermine both and cause heaving of the concrete?

[Tony Hwang]

I am in colder Alberta, every house we had built had rebars connecting garage floor and driveway. Expansion strip was always there. If garage floor and driveway bed is well prepared there won't be any problem. If the concrete work was shoddy all kinda problem will occur. Common mistake is laying the rebars flat on the bottom of slab. It should be imbedded in slab.

[Don Y]

Probably not. Most driveways are poured over a foundation of gravel to facilitate drainage. The risk is that water will *sit* just under the concrete and, being that close to the surface, will freeze and lift the concrete (water expands as it freezes).

Here, for example, our frost line is relatively shallow. It is unusual for us to experience many cold days/nights so the ground never has a chance to "freeze" -- to any depth.

As a result, many roads are poorly built -- sitting virtually atop the "dirt" beneath (no drainage). The inevitable cracks in the roadway allow water to get beneath it. If we have a particularly cold winter (or, several consecutive cold days) the water is close enough to the surface that the roadway (asphalt) is ruptured by the expansion beneath.

These additional cracks lead to more water infiltration... more heave... more cracks, etc.

Is there some reason you/your hubby don't want to fix the problem? It's not a huge undertaking, doesn't require special tools or knowledge -- just time and a little money.

If he's objecting to any work towards this, ask him what he *thinks* the role of the felt strip may have been... why did the builder bother to put it there? If it is just a *spacer*, why didn't he use a piece of wood? Or, pack dirt into that area? etc.

[Susi]

He says its used when concrete is poured for expansion when curing and not needed after that has occurred.

[Don Y]

If he believes this, then won't the veracity of that claim end up, ultimately, be *his* problem to sort out? If he's right, he wins! If he's wrong, *he* loses!