What type of control joint is best for my concrete project?

Question

I'm looking at getting a lot of concrete work done and am looking to educate myself past the minimal anecdotal information I posses so that I can have a better conversation with prospective contractors.

• Expansion joints, saw cut or hand troweled - is this just preference or is there a good reason to go for one over another? From an aesthetic perspective I like hand troweled but I've been told that the saw cut can leave the concrete stronger as you are interacting with the wet concrete less.

Google doesn't seem to provide much info by way of POV on this, just that there are options, so I look to the community here to see if there is a collective wisdom.

For perspective, this is for a standard 4" thick driveway, 6" thick apron, and garage floor.

Answer 1

Cut joints are smaller and straighter, generally speaking. I personally prefer them for that reason. They do require a return visit, however, and therefore may cost more. One possible downside is the sharp edges that are left, which can chip away and degrade appearance depending on the use case.

Tooled joints can be done at finishing time, and if done well don't degrade from the final appearance of the project. They are larger, though, and therefore can collect more debris. They do tend to be more durable due to the rounded corners.

A quick search does return quite a bit of discussion on this.

Answer 2

Space joints (in feet) no more than 2-3 times the slab thickness (in inches). A 4" slab should have joints 8-12 feet apart. Idon't like to use hand tools, because you usally don't get a deep enough joints with the jointers you see at Home Depot, Lowes, and such. For a 4" slab you'd have to utilize a commercial grade jointer, and for the price you'd be better off renting a concrete saw. There are 2 types available. one that is hand held ( looks something simular to a chainsaw ) and one which is on wheels that is usually more precise than the hand operated ones. Depending how many joints and the thickness thereof, you may want extra blades. You can save money on the hand held, if your confident, go for it. Either way, cut joints deep enough to be 25% of the depth/thickness of the slab. Make sure to utilize expansion material, such as asphalt board to cut your own ,or other commercially available, (already 4" height) also there are quality materials sold online in rolls, or available through the concrete ready mix companies. for this purpose. Use anytime between an existing strcture and your new slab, or between an existing slad and your new slab. Or it will cause problems like cracking or even leaks if your going up against a foundation, because the old and new will expand at different times. As far as the mesh goes, either type is exceptable, a lot depends on your slab size, because the rolls are sold in 150' lengths and there may a lot left over. The mesh should be placed in the middle of your pour (bottom to top)so you'll avoid any rusting, which happens when wire is placed too close to the top of your slab, or in the event that you get cracks later on down the road. there are a few different ways to accomplish this. You can pour half of your thickness first, and then put your mesh down, followed by the rest of your concrete. A second method involves putting your mesh down and using a hook of some sort to pull the mesh up halfway as you are pouring the slab. There is a third method where commercially avaible mesh and rebar chairs are used to set the rebar and or mesh on. This process isn't used much though for just a residential slab. Anouther thing to consider is, if you want to utilize plastic and pea gravle as a part of your project. The pea gravel is used for drainage, and a good subase for support. While a good 6 mil plastic is used as a vapor barrier. Either way, you should compact the subgrade( on good dirt) or the subbase if you use pea gravel. The subase isn't essential if you have good clean compacted soil. However it's a good idea to use 6 mill plastic as a vapor barrier which will help if your in an area where tempatures dip below freezing. Good Luck!