Whats is an "EXPANSION JOINT", when dealing with concrete.?

Question

My inspector wrote a note stating i need an expansion joint around foundation where new concrete will come in contact of home. So what is this expansion joint and where can i get some?

Answer 1

Expansion joint material is like a 1/2" thick tar or rubber impregnated heavy felt usually 4" or more wide used to butt 2 large slabs of concrete. It is used to absorb expansion and contraction and control cracks and splits in concrete.

If you can't find it at a home center try any of your local concrete companies. They can't live without the stuff and will probably sell you as much as you need. Your concrete supplier might also be a great source.

Assuming you are pouring the concrete yourself, you can slip it in after you have laid the concrete but before you finish it instead of trying to keep it in place during the pour. You can cut a trough with a pick and then insert the joint material. You might be able to keep it in place using your rebar or rewire that I am sure you will have to use in your slab but it often gets knocked around during the pour if its not held pretty securely.

Good Luck!

Answer 2

Where the new concrete comes in contact with the old, the concrete will move at different rates. At these locations, the new and old are usually separated by a felt-like material that may be 1/2 thick or so. Then a bead of sealant is placed over the top of this to seal out moisture.

I'm checking the web to see if I can find a picture...

This is as good as I can find http://www.pavingexpert.com/concjnt1.htm
All your really looking for is a control joint. A control joint is basically an admission that "the concrete's gonna crack, so let's try to control where it cracks".
You can saw a 3/16" wide cut into the concrete about 3/4" deep and this will force the crack at this point. Fill the saw cut with a high performance sealant that will allow the concrete to move a bit.

Good luck

Answer 3

Changes in temperatures cause concrete to expand and contract. If this movement is allowed to happen at random,a pad or pathway will crack at the weakest or most vulnerable point. Control joints,which are made from a compressible material, will either absorb the movement or concentrate the force in a predetermined area where it will do little harm. The joints should meet the sides of a concrete area at 90 degrees,more or less.

Answer 4

an expansion joint is a point where the concrete does not meet the rest of the concrete. This is on purpose so that the concrete can expand and contract with the heat and cold it will experiance. With out it the concrete will crack and crumble. A good example is on concrete bridges. Usually on a highway. Go look sometime.

Answer 5

there are 2 types that we use here, one is called homosote, it looks like the gray cardboard on the back of a school tablet but is 1/2 in. thick. the other is a tar strip about 3/8 thick. i prefer the homosote but its a judgement call. snap a chalk line on your house wall where you want the grade of the concrete to be and tack it up with some masonry nails. you dont have to sink the nails in all the way, just enough to hold it there till you get some concrete against it. put it up just before you pour or it will be a wavy mess if it gets wet too far ahead of time.

Answer 6

expansion joint stays put and its a cardbaord tipe filler to seperate every sixfoot and were floor meets walls its black and about 3 n half ich and 6or8 foot long lumber yard or home depot i am not quite so sure you run it along house though he just might be busting your balls ive really dont recall seeing that that particular way only for seperating every six footand if its done every six foot the expansion will take place i think along house will cause leaks so dont listen to all the idiots on here you better check with mason or foundation pro

Answer 7

Go to Home Depot its a black 1/2 inch wide rubber felt like stuff just ask em they got it