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Concrte steps

Concrte steps

Concrte steps

(OP)
Some newly placed concrete steps were made with the treads only 11.5" wide. These steps comprise 2 risers and 1 tread, and are located at intervals along the landscaped walkway. The walkway is the main entrance and exit to a place of worship. It is wanted now to increase he tread width to 14".

Attached are three options that I have come up with for making the reinforced concrete tread 14" wide. Each seems to me to have its pros and cons, but I am particularly interested in your comments on Option 3 (drawing SK-3). Can the concrete be cut back as I have shown? My reservation about that option is that it would be necessary to chip out at least some of the concrete and this would leave a rough surface; also the existing rebar ends would be exposed; also the sawcut would leave a sharp corner at the top of the riser.

Option 1 is likely the most economical, but it leaves the overhanging concrete subject to frost heave. Similar frost heave issue with option 2.

Anyone have any other way to make the 11.5 inch wide tread 14" wide?

(I was not involved in the design of the steps. It was done by a landscape architect. After it was built a number of people in the congregation questioned the tread width, and one person fell within a week of opening the walkway to use).

RE: Concrte steps

What format are your attachments in? It won't open for me.

Jim

RE: Concrte steps

(OP)
pdf created in Blubeam.
Please try the second submission that I sent with attachment and let me know. It should open ok. The first attempt that I sent with attachment would not open for me either, but the second attempt would although it took a while to open.

RE: Concrte steps

Number 1 looks good providing you properly bond the new to the old concrete. Parging with a paste of Portland on DRY, clean surfaces holds very well.

No. 3 will show rust at the cut off bars and how do you get s smooth cut for the horizontal cut flush with tread? Perhaps with a concrete cutting "chain saw", but difficult.

RE: Concrte steps

(OP)
yes oldestguy, those were my thoughts as well regarding option 3.

I had not thought of bonding paste for option 1, but I can add that to it. One thing about option 1 is that there could be frost heave force exerted on the overhanging part, which leaves me a little uncomfortable. To excavate it down 4 feet though would be a significant cost.

RE: Concrte steps

Your first attachment does not display a pdf extension and your second attachment returns an error message with a note about double headers and also does not open. I have opened Bluebeam pdf's on several occasions so I don't think that is the problem.

Jim

RE: Concrte steps

I like Option 1. If the pavers and existing steps are not susceptible to frost heave then shouldn't the added step be OK?

I also like Option 3 but it'll be a bit of a pain since the concrete has to be cut out with a chop saw or line drilled. You can grind it for a smooth surface or over cut it a bit and put in a new facing on both surfaces. It could help with preventing rust stains from coming through.

RE: Concrte steps

(OP)
ok, thanks all for the comments. I don't know why some can open it and others cannot. I tried re-posting it and opening it, and now I cannot open it! So I don't know why. Maybe it does not like bluebeam, or maybe there is something wrong with the forum system at the moment. I'll try later in the day. sorry.

RE: Concrte steps

I would vote option 2.

You won't be able to cut 3 well. 1 is too small to do properly IMO.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

RE: Concrte steps

Option 1 or then 2 is my vote. If you are concerned about frost heave in Option 1, cut the s.o.g. back and cast the riser extension either of a void or taper the bottom surface to minimize the potential area frost could push up on.

RE: Concrte steps

About frost heave: Tapering the bottom won't work. However replacing the paver section below with Styrofoam, the pink stuff, will do the job. It needs to be closed cell foam so as to not take on water. Leave none exposed to sun.

RE: Concrte steps

(OP)
Thanks Bridgebuster - Heave of the pavers is not as big an issue as heave of the concrete because the latter may result in cracking of the added concrete in option 1, or cracking of the concrete and lifting of the step in option 2, that cannot be simply reset like the pavers. The existing concrete extends all the way down to 4 feet below grade, below the frost level.

To dcarr82775 - I had thought of both the ideas you suggest to relieve frost heave, but was not comfortable with either of them because the pavers might eventually drop down due to settlement of soil supporting the pavers into the void; there is no slab under the pavers. Angling the projection is a way of improving things, but again it would make compaction of the soil more problematic and adfreeze forces might still result in uplift force, but I will give it more thought. Thanks.

I assume that no one sees any options other than the 3 that I have suggested?

I don't know what the problem is with opening the attached file. Although before I could open it, now I cannot! I wonder if something has gone wrong with the Engineering Forum software...are you able to upload and open any of your pdf files created with Bluebeam?

RE: Concrte steps

Why are you going to a 14" tread? That is a non-standard gait and can present problems negotiating the steps. What does your code say about riser/tread ratios?

RE: Concrte steps

(OP)
To Ron: For exterior walks with only 2 risers, a 14" wide read is frequently used, combined with a 5.5" riser. This gives a product of rise times run of 77, which is close to the 75 recommended by Architectural Graphic Standards and goes well with the slower walking gait for this type of 2 steps in a long exterior walkway, and is recommended by landscape architects. When there are only 2 risers, a short tread presents particular problems and a wider tread is preferred. This is different for flights of stairs in a building where the gait up or down a flight of stairs is more deliberative, and in any event the floor to floor height and plan space limitations preclude the use of a wide tread in most buildings. There are a number of good articles on the internet for the proportioning of this type of step and I urge you to read them. We have actual experience both with a 11.5" tread (and 2 risers in a long walkway) and a 14" tread (and 2 risers in along walkway) and the 14" tread is clearly superior. Again, I emphasize that I am not talking about a flight of stairs within a building.

The building Code applies to the building. The exterior landscape steps are not covered by the building code, being as they are well outside the building. We confirmed this at the outset, with the building department, and a thorough search of all building code provisions pertaining to steps. However if they were covered by the building code, there is nothing in the building code against a 14" tread. Although not covered by the building Code, the general rule is the wider the tread, the shallower the riser should be.

To oldestguy: Styrofoam is not very compressible, certainly not enough to absorb frost heave. We never use styrofoam when we are looking for compressibility. The beadboard is more compressible, but of course that will take up water so is not acceptable, as you have noted.

RE: Concrte steps

ajk:

For what it is worth I just took a 2" square section of 2" thick pink stuff and squished it to 1 inch height. It moved up to 22 psi on the way and then leveled off at 30, and then dropped gradually. Removed load and sample returned to 1-3/4". Ran several more cycles to 1" and return generally to the 1-3/4 mark. In the process of sitting at 1", each time the load dropped off toward the 22psi level. Thus, I'd not be too unhappy with a, 8" stack of pink stuff under the new extension. How much lift is common there with current pavers?

RE: Concrte steps

(OP)
The pavers were just installed in September so I don't know how much lift there would be due to frost heave, but I would not expect it to exceed about one inch the first winter.

Your tests are quite interesting...did you do that in a lab?
What do you mean by "the pink stuff"? Dow Type SM insulation (in Canad, or Dow 35 psi insulation in the U.S. I believe), is what is usually used here in Toronto, except under pavement with vehicle traffic, in which case the HL40, HL60 or HL100 would be used, depending upon the stress on the insulation. A pink stuff is made by Owens Corning, and like Dow, they make several different grades, but is identical to the corresponding Dow grade...at least that is what Owens Corning told me a number of years ago! Which grade of the pink stuff do you have, and is it the Owens Corning product?

You say that it moved up to 22 psi and then leveled off at 30 psi. I am confused. Do you mean it moved up to 30 psi and then leveled off at 22 psi?

RE: Concrte steps

OK here is some info. I gave away a bunch of lab equipment a few year's back but retained a Remac Valve spring tester. It was a handy device for quick unconfined compression tests where both load and deflection can be read as you go..

The stuff is Owens Corning FOAMULAR 250, commonly used for house insulation board. Extruded Polystyrene (XPS). I use it for covering my hot tub after the beaded stuff soaked up water.

I ran another test this AM and recorded the data. I then put it on a spread sheet and could have printed it or sent a file. However, here is a photo of my screen.

At the top of the load, as the deflection was reached and held, the load dropped off. For instance, the 0.875 deflection load of 110 dropped off to 100 pounds and still moved but more slowly. The 0.50 inch deflection went back to 0.25 inch and the 0.75 inch deflection dropped to 0.375 after each load removal respectfully.

It would appear that a form of "spring effect" is present so permanent deflection won't happen leaving a place for snakes, etc. under the step.

While this compression load capability is pretty good, I'd suspect the total weight of the step system is such that frost heave won't lift anything. Of course that bond and reinforcing must hold. That Portland cement paste thing is great. I have taken cores of a joint of old and new concrete and then take a chisel to that bond and the break is always in concrete away from the joint. The reason appears to be due to the dry concrete taking in the cement in pores there.

RE: Concrte steps

(OP)
oldestguy that is great information. I wish I had a device like that at home to do simple tests. I will look into that insulation and see if it marketed here in Canada (where are you located). Like you, I suspect that the frost won't do much to it, but it is not good practice to leave something subject to frost heave, so to be prudent maybe what you suggest with the insulation is the way to go. Thanks very much. Very much appreciated.

RE: Concrte steps

(OP)
Does it say that FOAMULAR 250 is water resistant? Styrofoam under some northern climate environments can become waterlogged...I have seen that myself in plaza installation in Toronto , and Dow's engineering department in the U.S. agreed that this has sometimes happened in northern environments. They recommended not placing concrete directly in contact with the Styrofoam. When I discussed it with Owens Corning, they told me that since their product was the same as Dow's, then I ought to follow Dow's advice!

RE: Concrte steps

Old guy back here: It does not say anything about water resistant, but I have understood it is closed cell and my use here in south-central Wisconsin shows it is. For instance for the hot tub cover application now in former log home no sign of added moisture in it with one such use 20 years and in another here for 4. At earlier home it was used for insulation of septic tank lid in all kinds of weather always showing no absorption any spring season when removed for the summer. It was used as basement wall exterior buried insulation for at least 5 years and when exposed for the addition showed no water take on. In roof insulation for log house, where condensation from below might occur, the exposed stuff when exposed at addition area showed no sign of moisture such as mold or rotted sheathing. At that addition project a building engineer friend of mine warned that such "sandwich" construction results in saturation and rotting, but no such thing happened that I could see. I used it under basement slabs for two new houses built, but of course no way to check, other than to observe no settlement and comfortable winter use situation.

RE: Concrte steps

(OP)
ok, thanks very much for this information.

RE: Concrte steps

O.G again:

If the concern is the 250 strength, and even the 150 is too strong, consider pourable foam from mixing two parts. .

It came up under a search for Two part closed cell foam. Apparently this product is closed cell (for floatation), but I didn't see strength properties

I have used these foams to fill large cavities for a catamaran as well as the electronic transmitter-receiver filter for a ham radio repeater station.

http://www.fibreglast.com/product/2_Lb_Polyurethan...

RE: Concrte steps

(OP)
ok, you are way ahead of me. I will check out the links that you sent. Thanks again.

RE: Concrte steps

(OP)
I am a little worried about option 1, that the existing concrete, which is several months old and will have undergone some of its long term shrinkage, will restrain the shrinkage of the new concrete and cause cracking of the new concrete (i.e. cracks transverse to the treads). The longitudinal bar is intended to control the width of the crack, but I think even small width cracks will be visible when the concrete is drying after a rain, because the crack takes longer to dry than the adjacent concrete. I don't know how to get over that issue, nor how to calculate the crack width for a given amount of steel. What do you think - is this something that I should be concerned about?

RE: Concrte steps


Careful when testing small samples and projecting the results to large pieces. Edge restraint conditions can skew the results of the smaller sample to give greater apparent flexibility than would be experienced by the large piece. Think of perimeter to area ratio. Also see calculations for elastomeric bearings.

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