Diamond Dowels 3

[JoeBaseplate]

http://www.pna-inc.com/products/diamond_dowel/

Has anyone used these dowels on slab on grade const joints? The contractor is requesting to use these instead of the typical dowel between pours detail and he claims that this will help reduce curling in the floor, which I don’t buy. But regardless, has anyone allowed the use of these on any project and what has been the experience.

Thanks.

 

[hawkaz]

I have had very good luck with this product. Used it several times, haven't had a call back on one of these slabs yet.

These are expensive, but you get the Cadillac of slabs.

They do help reduce curling better than convensional dowels. It's a simple matter of surface area contact between slabs. With a solid flat plate, you will get considerably more contact area than a 1" diameter smooth bar.

 

[hokie66]

You must have a very good contractor. The primary benefit of diamond plate dowels is that they allow the slab to shrink unrestrained both parallel and perpendicular to the joint, thus avoiding shrinkage cracking initiated by the dowels. Just make sure that the dowels are parallel to the slab surface, and that the concrete is well consolidated around the dowels. I am skeptical that diamond dowels would minimise curling, but that would be another good thing.

 

[RacingAZ]

hokie, I'm thinking the same thing. OP should be thankful the contractor is asking him to use those dowels. I spec them on some of my projects and my experience is that some contractors would try to weasel out of providing them.

Although they are not primarily for curling, it's a definite upgrade from smooth round dowel bars.

 

[Ron]

Diamond dowels will not prevent curling, so don't let the contractor substitute dowels for good construction practices. As for load transfer...they are good. As someone noted, make sure they are parallel to concrete plane.

 

[a2mfk]

They better be good, using them on a big warehouse job that is about to get placed... But they come highly recommended by a respected firm here in FL that uses them all of the time. They also seem pretty easy to install so maybe that helps offset the upfront cost, and if you study their website a little you can see how they may be even better in allowing shrinkage of the slab then smooth dowels.

 

[JoeBaseplate]

Thanks for the feedback. I guess this will be my first project with diamond dowels.

 

[doka1]

As a contractor, we always submit diamond dowels instead of smooth dowels. They are far easier to install, and easier to maintain during the pour. When you think about these round sleaves for the smooth dowels you can imagine the concrete pushing them up and down. If you actually try to install the dowel itself you have to drill the pour stop which then makes it harder to strip. Be careful if your slab is 4" though, the min for PNA (manufacturer) dowels is 5", so you would have to haunch the slab at the joint. For warehouse slabs we also use dowel baskets to holds plates at the locations of the sawcuts.

 

[spats]

doka1... are you sure about 5" minimum slab for PNA dowels? By coincidence, I was just looking at using these in a high-end residential project where there will be a construction joint between the "normal" slab and a 1" recessed slab area that is to receive cast stone (I want the stone floor area isolated for crack control). Because of the 1" recess, I will definitely have to haunch the "normal" slab at least 1" (maybe not practical), but I would need to haunch the lower slab as well? I found one place in PNA's literature where they reference a 4" slab in their chart. Of course, I'm not talking about transfering any great loads here across the joint. I'm just trying to keep them from moving up-and-down relative to each other.

My next step was to contact PNA, but I thought I'd get your opinion since you guys are coincidently on the same subject.

 

[a2mfk]

spats- I believe these minimums are more for load transfer in warehouse floors, ie forklift wheels that cross the joints. For a residential slab with little LL, I think you'd be fine even though it seems like overkill. A simpler construction joint may work fine for your application.

 

[spats]

a2mfk,

Why do you think it's overkill? I need something to tie them together so I don't get get differential vertical movement, and the PNA doiwels allow movement in the other two directions. Movement in two directions is important because my recessed area is a very odd shape (not rectangular), and keyways are pretty much frowned upon these days.

 

[a2mfk]

You said its a high end home so maybe the GC won't balk, but most would... Residential slabs are very lightly loaded, per square foot most of the weight is the slab itself, so a less robust joint would likely be adequate for most situations. But I like diamond dowels so if you want to use them, go for it!

I think with your detail I have usually used a continuous concrete placement detail with no joint, and a haunch that transitions over a foot or two to avoid a sudden change in the thickness of the slab to lessen the bottom restraint of the slab in shrinkage. Usually put a cont rebar in the haunch parallel to the step.

Lots of ways to skin this cat, we are probably giving it much more thought then 99% of house designers

I'd also be concerned with the transition between the stone and your other flooring at that joint, though its not your detail its something worth coordinating with the architect. You could get continued slab shrinkage down the road depending on how quickly they place the flooring (and lots of other factors) and get some lateral displacement that may cause a crack at that joint if rigid material is placed over top of it. I often see tile cracks in residential SOG placed over construction joints and shrinkage cracks that do not have vertical displacement, only lateral...

 

[spats]

a2mfk,

Thanks for the response. I fully intend to coordinate the transition detail for the finishes with the architect. Any internal sawcuts within the stone area will need to be coordinated with the tile pattern, with a flexible joint between tiles in lieu of grout. Just so you don't think I'm going crazy on joints, the footprint of the first floor of the main house is over 8500 sq. ft.

I'm beginning to feel like I'm hijacking this thread. If I need more input, I think I'll start a new one.