Geo-textile Placement

[Lanelle]

I'm wondering if ICPI has changed recommendations for the placement of the geo-textile layer under pavers? When I went to the basic contractor training, we were instructed to place the fabric on the compacted sub-base, followed with the compacted lifts of base material. I have heard that there are other recommendations now but not sure why.

As a side note, I tore apart a failed installation that had a thick, non-woven filter cloth underlayment between the base and the sand. The paver tops were the only thing intact. The bottom of the pavers had turned to sand and gravel with a heavy salt residue. This was in a heavily used pedestrian area that had been heavily treated for ice control for several years.

I'd like to see your thoughts on this.

[Stonehenge]

That is veryinteresting...

I'm no engineer (though I see that many of our newest members are, so maybe they could weigh in on this topic), but I would bet that if there was a thick fabric separating sand and crushed stone base, that the fabric is holding up all the salts and minerals and causing the breakdown. I would love to see some pictures of that - did you get a chance to snap any off?

Also, were the pavers clay or concrete? Since you mention ICPI, should I assume concrete?

You mention a change in ICPI specs - what is the new method they now endorse?

[Rex Mann]

The ICPI has not changed their basic recommendation of installing the fabric under the aggregate base material. However, there are times when deviation from this practice is required.


It is important to know the differences between woven and non-woven geo-textile and the appropriate use of each in a given environment.

I've seen a job where a beautiful multi-level Versa-Lok wall was built. Only to see it 2 months later in complete failure, it toppled over and slid out. Come to find out, the contractor used a substitute for geo-grid. They thought orange snow fence would work just as well. No joke! They used orange snow fence as geo-grid.

Not only do you have to know the "ingredients" to build a proper hardscape, but in what order they are used also, what can be used as an equivalent substitution.

Peace,

Rex:

[Lanelle]

On that failed project that I contracted to repair, what happened is that the fabric silted closed and held the salt against the pavers. I thought I had some pictures somewhere and maybe even posted a couple but I have no idea where they are now. If I run across them, I'll post the photo of the roll-off full of what looks like paver veneers. Yes they were concrete.

[PSUscaper]

hello,

I remember paul mentioning something about the use of fabric behind retaining walls.....I think it was along the lines of the problem with the fabric under the pavers.........eventually the fabric becomes clogged and allows nothing to pass through

I can picture this happening the more and more I use fabric. Imagine the fabric clogging and then the water pushing on it, pushing the wall over.

I'm really starting to question the use of fabric behind walls. I like the idea of just using more clean 3/4" stone instead. I thinking about just wrapping the drain pipe in the stone with fabric, if anything.

The last seminar I went too they recommend using geo-tex under ALL paver installation. I still do not like the idea. In a competitive market, where nobody uses geo-tex, it is very difficult to justify a extra $1.00 per sq foot into the jobs and talk to the people about it.

Second of all, its hard to know if your going to need the geo-tex until you really start digging. I always figure its cheaper to dig a little deeper and put in more base rather than using the expensive geo.

As I have mentioned before, I'm not to quick to jump on any 'guidelines' ICPI has. I firmly believe many of these so called 'guidelines' are nothing more than easy way outs for paver manufacturers to cover their buts in case of product failure. After my feud with a them on a job where pavers were going on top of concrete, they greatly disappointed me. Bottom line is that their is more than one way to skin a cat. Paver manufacturers would think otherwise, as would most engineers.


steve

[Rex Mann]

When I worked in Ohio I always used fabric behind walls and under every paver job. I swear by it. Here in Phoenix we do not use it. Jobs in Flagstaff, which has freeze-thaw, we use it. The soil there needs it.

We pay about 7 cents a square foot for our geo-textile. I looked at it as cheap insurance.

Peace,

Rex

[PSUscaper]

I have a quick question:

what is the main purpose of a geo-textile under pavers?

Is it to stop the sub base from contaminating the stone base??

or is it to span any voids that may form in the sub-base eventually and support the bricks from sinking in??

At the last seminar, they stressed the second use. If something were to settle underneath the stone base, the geo would span the weak spot and support the pavers. (for example......you dig out a walk, and have to remove a large rock.........as we all know, it is going to be very difficult to get that one spot compacted enough, and eventually, it will settle a little more than the rest of the sub-base..........therefore the geo-tex 'spans' the area, supporting the pavers)

I can't remember the technical name for the fabric they had, but it wasn't just a filter fabric. It had 'structural' strength to it and if needed to, it would support substantial amounts of weight. It was much heavier than regular fabric. Kind of reminded me of a geo-grid and filter fabric layered together.

Most geo-tex's are not this product............this stuff was expensive.....like over $1 per sq foot......filter fabric is cheap.

I wonder if anyone could clear this up with me.

The seminar was a belgard one and they were pushing their own 'brand' of fabric, so maybe this was just a scheme to sell overpriced geo-tex.

I think there is a lot of mis-information on what the proper fabric to use is and what its purpose is.......

Also, thinking back to lannelle's failed paver job................if a area is being heavily salted, do you think the fabric made that much of a difference??? I mean, fabric or not, salt is going to seep in and stay in the sand. Wouldn't you think the reason for this is something else......like not enough base material for proper drainage????.....maybe a pour sub base that allowed no drainage at all???? or maybe the area was always wet (high water table)???? I think the fabric may have been part of the reason, but not all of it........in fact, I think the main problem was the use of salt!!!!!!!!!!! No matter what, if a area is heavily salted, it is going to cause damage to the pavers.



steve

[Stonehenge]

I think I've used the kind of thing you're talking about - it's woven, and actually serves as something like a geogrid. Versa-Lok makes some called Versa-Fabric, or something like that. Looks like silt fence, if you were comparing it to something.

[Paul]

There are about 400 different fabric/geotextiles, all will support some weight distribution. You need to spec the right stuff for what you need it to do.

Steve I think your right, salt in liquid form will not be stopped by simple fabric underlayment. But it might hold water laden salt due to poor drainage. We have never installed a geotextile between the base and sand layer, all geotextiles are installed between sub-base and base. This installation should extend well passed the edge of the pavers other wise you lose the edge support it give along with undermining that could occur.

[agla]

I don't know if one of the engineers or soil people can back me up on this, but when you have a material with tighter voids over that which has bigger voids it will hold water much closer to saturation before giving it up to the material underneath.

Salt will stay in that material as the water dries out. The process repeats and repeats. I think that it would get worse because the salts will make it even harder for that layer to give up water. So, the salts would just build up and up, I think.