Pros and cons of compacting bedding layer? - Why is it done?

[LandscapeMann]

I have seen mention here of compacting or partial compaction of the sharp sand bedding layer. The specifications of the pavers I use over here in the USA don't refer to that method.

Do you use the vibratory plate compactor to compact the 1" (25mm) of bedding sand?

How does one do partial compaction?

I have had very good results screeding the 25mm bed with out compaction as per the instructions that I have seen. But that is also in conjunction with having the stone base very compact and to grade and sand bed depth consistendly 25mm.

LM

[84-1093879891]

I can't really comment on US practices as I have no direct experience, but they do seem to be a little bit naive compared to our way of working.

The three acceptable methods of screed prep are described on the Screeding page, but for myself, and most other British and Irish contractors, the pre-compaction method is the preferred option.

And we use a minimum of 30mm sand, not 25mm. Most Contractors work with 35-50mm for the laying course. I wonder if your 25mm spec is because of frost heave problems?

Anyway, have a read of the page mentioned above as it explains how each method is actually done, and the pros and cons of each.

[LandscapeMann]

Thanks Tony,
I read the screeding pages and have a better understanding.
I will try the pre-compaction method.

Due to the frost heave overe here. I use the snap-edge plastic edging which is approx .6 the height of the pavers, leaving some play for the final compaction. So I am not ususally laying to a exact fixed height edging. So as long as the the bedding sand is of a uniform depth. The finished pavers compact very evenly.

Sorry if this does not sound to clear.

I do see the advatages of your pre-compaction method and look forward to giving it a try.

LM

[84-1093879891]

Every couple of years or so, a British manufacturer or importer will latch on to those plastic-edging yokes that are popular in the States and decide they are just what we need over here. 12 months later, when they've still got 99% of their original stock left cluttering their warehouse, they realise the truth in the old adage - if it ain't broke, don't fix it.

Concrete bed and haunching works supremely well for paving in Britain and Ireland and the vast majority of contractors see no point in changing methods and buying bits of plastic, tubing and ground spikes that cost around 5 times the price of concrete. I can see the advantages when these edging systems are used in a climate subject to frost heave problems, but they are a waste in these mild-but-soggy islands.

[LandscapeMann]

Yes the snaplock edging can be a bit of a pain to install and the 3/8" X 12" spikes every few inches gets pretty expensive at today's steel prices! But with the frost heave seems to be the preferred method here.

I was surfing through the EP Henry (Paving Manufacturer) web site FAQ. and came acoss the following:

"Tell me about the sand setting bed...
The material for the bedding layer should be coarse concrete sand. Do not use stone dust or screenings; it does not allow the pavers to seat properly and tends to break down over time. The sand should be an even 1 thick layer. Do not compact the sand setting bed. Do not mix portland cement into the sand used for the setting bed or the joints between pavers. It defeats the flexibility of the system and it cannot be cleaned off the surface of the pavers"

I don't know if frost heave has anything to do with the 1" (25mm) laying bed. Or with the "Do not compact the sand setting bed" instruction. Or with the "do not mix portland cement". But my guess would be that frost heave factor may be reason for the difference?


LM

[twodose]

Concrete Bed and Haunching:

Is this just a dry cement mix that is compacted for the edge course to lay in?

Then by haunching I guess they mean to add more dry concrete mix to build up behind the edge course to " hold it in place".

This looks like a great idea and would give you a good level guide for screeding if it is put in right.

It is hard to compare what we do in a climate with frost and heaving compared to a climate without.

Not to say that this dosen't work well in a no frost climate,as I am sure it does, but I am going to call EP Henry and Hanover and ask them about doing this in our climate.

[84-1093879891]

The bed and haunching is usually a semi-dry or moist mix - just enough moisture to initiate curing of the cement content.

A fuller explanation of how edge course are laid and haunched is given on the main website.

[LandscapeMann]

Twodose,
Let us know what EP Henry and Hanover say on the subject.
I don't recall if it was addressed on there website or not.
LM

[twodose]

LM

EP Henry says no pre-compaction for the sand bed. Talked to Mark Antunes.

He also said that the concrete bed and the haunching is the old way that it was done, before they had the plastic edging. He said that the concrete bed should not be used in areas that get frost.

They don't have to worry about the frost and heave problems we have here so it should work well for them.

I haven't talked to Hanover yet, but I would think there views would be the same.

[84-1093879891]

Do EP Henry have a reason why the prefer no pre-compaction? I usually run into a troop of EP Henry people at Glee, so I'll see if I can get an answer from them, but it would be good to hear what the US-version of the reasoning is.

I can understand the point about concrete and frost heave, but I do feel that relying on a concrete bed and haunch allows us to be far more creative with our designs, and enables the creation of more natural looking curves and arcs, especially those of a fast radius.

[Paverman Dan]

What on Gods Green Earth are EP Henry guys doing in ENGLAND? LOL

JMHO . . .from a Yank point of view:

Plastic edge restraint goes in faster. Its lightweight and easy to transport . . as opposed to concrete, IMHO.

While frost heaving in the US is a good reason to consider not using a concrete curb which will eventually crack and fail, frost heaving in the base may cause the edge restraint to "pop up" where it could become visible above the surface of the pavers. (Hammering spikes all the way into the base on a plastic edge restraint makes this problem worse: it makes the spikes "pop out" during freeze-thaw cycles; I recommend using a rusty spike, but not hammering it in all the way.)

So the main benefit is ease of installation.

I've used plastic edge restraint, Pave Edge flexible kind, and you can bend it to get the curves, and I find it pretty easy to work with, and effective. Concrete is on its way out in this part of the States, anyway. And Tony, trust me, if you knew how many contractors in the States don't use ANY edge restraint . . .you'd be thankful some even use the plastic stuff! LOL

Belgard, another North American manufacturer owned by Oldcastle, also reccomends NOT compacting the setting bed. I think I pointed this out in another thread, but the theory is compacting the setting bed makes it difficult for the particles of sand to get into the joints when compacting the pavers into the setting bed.

That is what the ICPI sez anyway . . that said, Tony's wisened and time tested arguments for pre-compaction are worth studying too.



Edited By Paverman Dan on 1095999759

[84-1093879891]

Well, I never got the chance to interrogate EPH's delegates to Glee - they seemed to spend most of their time in the bar with occasional visits to the Charcon, TopPave and Marshalls stands so they could legitimately claim to be working! :;):

I've seen the stuff from Belgard and I don't accept their premise that the bedding sand needs to enter the inter-block joint. I've seen, from paving we've had to lift and re-lay for whatever reason, that even with a pre-compacted bed, the laying course sand gets into the joints by a millimetre or so, which is sufficient to lock the paver in position, and then the jointing sand fills the gap and generates the friction interlock.

Incidentally, there's a small piece in my Glee Show Report looking at the plastic edge restraint system from Aco, which they've dubbed 'Borderguard'.

[Paverman Dan]

Well, I never got the chance to interrogate EPH's delegates to Glee - they seemed to spend most of their time in the bar with occasional visits to the Charcon, TopPave and Marshalls stands so they could legitimately claim to be working! :;):

I've seen the stuff from Belgard and I don't accept their premise that the bedding sand needs to enter the inter-block joint. I've seen, from paving we've had to lift and re-lay for whatever reason, that even with a pre-compacted bed, the laying course sand gets into the joints by a millimetre or so, which is sufficient to lock the paver in position, and then the jointing sand fills the gap and generates the friction interlock.

Incidentally, there's a small piece in my Glee Show Report looking at the plastic edge restraint system from Aco, which they've dubbed 'Borderguard'.

Ha! Typical American concrete salespeople!

I enjoyed that Glee report. The availability of pavers and slabs in the United States is light years behind that in the UK, hopefully we will be getting those kind of products here soon.

[LandscapeMann]

Another update:
I used the pre-compaction method as per Tony's specifications for both the front walk and rear patio. I also used approx. 40mm bedding layer as opposed to the 25mm that EP Henry calls for.
I was very impressed with the pre-compaction method. I had to meet the existing grade of my overlaid front stoop on the front walk. So I did not want the pavers to settle to much when I wackered them.
On the rear patio. I started to lay the pavers with out pre-compaction. But with the bedding layer being fairly damp sand. And the fact that I was having to start my Heringbone pattern from a inner corner. The only way to get to it is over the sand. I quickly went back to pre-compacting.
The other point that is stated by the proponents of no compaction. Is the sand should be completely dry.
The problem with that is that we have already had a hard freeze. I don't think I will see any dry sand till next spring.

Anyway, thanks to Tony for introducing me to a new method. It really paid off on my present project.

LM

[Paverman Dan]

INFIDEL!
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Just kidding! I'm glad it worked out . . .again, ICPI guidelines are that: GUIDELINES, and even by their own wording, not industry standards (contrary to some peoples opinions in the US).