Rubber mat or not?

[PhilDS]

Morning all,

Quick question...do I need to use a rubber mat on the whacker plate when I'm whacking down my concrete block paving? The blocks are 200x100x50 Bradstones from B&Q.

Cheers,

Phil

[MRA]

Hmmm...a choice you need to make yourself really.

I know many contractors that don't use one, but you have to sweep the sand to a decent depth so you don't scratch the block face. One problem with this is that within even the better kiln dried sands there is always the possibilty of small stones which have got through the process leading to potential scratching from the stone being compacted into the block face.

It's preferential to use a mat when compacting textured blocks or else the look could be ruined.

One advantage of not using a mat is that any weakness in a block is more likely to surface because a weaker block may split on compaction. At least if its likely to break at some point, remedial action can be taken immediately. A decent block shouldn't be weaker but even in the premium ranges, product issues can occur occasionally.

[James.Q]

i personally dont use a rubber mat on concrete pavers. but i tend only to use 60mm blocks. when i have used the 50mm i tend to break quite a few on first compaction but at that point its easy to replace.
JQ

[Bob_A]

I bought a Wacker (without a rubber mat) to do a couple of block paving jobs using run of the mill standard concrete blocks, I then intend to sell the machine on.
Rather than go to the expensive of buying a rubber mat can I improvise. I seem to remember reading somewhere that you can improvise by tieing something like carpet to the bottom of the Wacker.
Anyone got any views on this.
Thanks

[MRA]

I bought a Wacker (without a rubber mat) to do a couple of block paving jobs using run of the mill standard concrete blocks, I then intend to sell the machine on.
Rather than go to the expensive of buying a rubber mat can I improvise. I seem to remember reading somewhere that you can improvise by tieing something like carpet to the bottom of the Wacker.
Anyone got any views on this.
Thanks

I wouldn't advocate using carpet on any project I worked on. You really should have saved your money in my opinion and hired a wacker with mat when required. Surely selling on even after a few jobs isn't economically viable?

[Bob_A]

I did look into hiring but the cheapest I could hire a Wacker was £48 + £9 for the mat a week inc VAT but excluding delivery.
Then you have to consider the speed I work at (dead slow) and then the weather, could be I'd need a wacker for a numer of weeks..
If you buy a secondhand genuine Wacker or other quality make and sell it on then there's no reason why you shoouldn't get most of your money back.
I think I'm in luck, I'm pretty sure the hireshop have the same Wacker as me so I may be able to hire out just the mat.
Although to be perfectly honest I didn't think I needed one, I thought mats were more for decorative blocks rather than plain concrete ones. It's only after reading this thread that I had second thoughts.

[Bob_A]

Morning all,

Quick question...do I need to use a rubber mat on the whacker plate when I'm whacking down my concrete block paving? The blocks are 200x100x50 Bradstones from B&Q.

Cheers,

Phil

Phil
I'm learning as well but this may help.
I found it on this page http://www.pavingexpert.com/archv109.htm

Rubber Sole on a Wacker - Martin B - Jun 11th 2003
Is it advisable to use the rubber sole on a Wacker when bedding in the blocks? My worry is that not using one will lead to damage or scratching of the blocks.
Thanks for your help and such a great website.

Martin B

Suki
Jun 11th 2003
If you spread the kiln-dried sand around generously where you are about to wacker, then the kiln will cushion the plate from the blocks. I sand every job and wacker without a rubber plate and never have a problem. I only use the rubber on clays.
Tony Mcormack
Jun 14th 2003 Most concrete blocks don't ned the rubber mat fitting to the base of the vib plate, as they are tough enough to withstand a good rattling, and, with the tumbled types, even if there was a minor amount of damage, you'd never notice. The flexible bedding actually helps absorb the force of the vibration, and so the blocks are spared the worst effects of the plate compactor. Consequently, rigid-bedded blocks should not be vibrated once the bedding/jointing has cured.
Clay pavers are often considered to be more brittle than their concrete cousins, and so many contractors choose to use the rubber mat when consolidating, but it's not always necessary - as Suki says, a good, generous covering of the jointing sand can provide a sufficient degree of cushioning, and the only real danger of spalling clay pavers is when, because of the slight deformations that are inherent with any kiln-fired product, two adjacent bricks are in direct contact, and so rattle against each other. Because concrete pavers have a high level of dimensional accuracy (usually), the odds on two pavers being in direct contact is much less, and so spalling is less likely.

But, if you want to err on the side of caution, then you should fit the rubber mat before final consolidation


Found this in the archives as well. Great website

paj
12th November 2002 Booked time off work, so i have friday sat. sun and monday to finish edges give sub base final going over and get blocks down. just a couple of question to help me on my way, the wacker i am using hasnt got a rubber plate is it a bit risky using it on blocks? when i lay the main area should i set them slightly higher than the edges to allow for wacking and if so how much higher? fingers crossed the weather will be kind to me this weekend and i can finally get it done.
cheers
paj

Tony McCormack
13th November 2002 Was it wise booking time off work? It's abso-bloody-lutely guaranteed to persist it down all weekend now!
Don't worry about the missing mat - it's not a problem with concrete pavers, other than the highly decorative types. For yer bog standard Driveline types or tumbled pavers, it makes no real difference.

Deciding just how 'high' to set the pavers depends on the bedding course. Some sands compact more than others., so, if I was to say to you leave them 5mm proud, you can be certain that would be either too much or too little. The only way to be certain is to do a test patch, but I appreciate this isn't always feasible on a one-off private driveway.

So, sticking my neck on the block, and assuming you are going to have a bedding course that's around 40-50mm thick, using a decent grit sand, then, assuming you go for the light compaction before screeding method, and you're using 50 or 60mm thick pavers, I'd risk saying you should leave them approximately 6-9mm high and this will compact down when you've done. Probably. Ish.

If in doubt, err on the side of caution - it's much better to have them 3mm high than 3mm low, as high blocks don't pond and they may well settle that last few mmm over the next 6 months or so.

I'll be thinking of you, when it's lashing down, and the wind's a-howling, and I'm watching Football Focus in front of the fire with a steaming mug of Bovril on Saturday!

[lutonlagerlout]

the carpet move is rubbish,i read it here and tried it once and it is a disaster ,the carpet kept ripping.
i use 60's and last time out got only 1 broken block out of 5000+ without a mat
clays you need the mat for sure
cheers
LLL

[Dave_L]

Nice generous covering of KDS and whack away (oooerrr!) in a criss-cross pattern.

Never used a mat on concrete (50 and 60mm) pavers.

[matt h]

generous coating of kiln dried and wack away imho. BUT LIKE LLL ONLY USE 60MM BLOCKS. Thinner blocks and clays would need mat.I brush in kiln dried then cover the area then wack three passes. havent had any comebacks so far

[PhilDS]

Thanks for all the replies. Good news then, I can save myslef a few quid and not have the mat.

I'll you know how many blocks "fail"

[Rich H]

I use 50mm pavers. Last job was 5000 with two cracked. Previous three or four jobs, same blocks, no cracks at all. Never used a rubber mat, but I've never done clay pavers, either.

[colordrives]

Never used a matt in the thousands of drives i have done, just spread lots of dry kiln, 50mm pavers dont crack at all, I dont remember the last time I had one break I and I use 80% clay blocks. So 50mm pavers DO NOT need a matt.

[seanandruby]

Never used a matt in the thousands of drives i have done,

did you know Methuselah personally?

[Tony McC]

The point about relying KDS as a 'cushion' is valid, but the latest edition of 7533/3 advocates compaction before jointing, as this enables easier removal of damaged blocks.

See the fuller discussion on this page

Having said that, the neoprene sole plate is rarely need unless there is an obvious reson to do so. Some of the more decorative blocks, and those with an exposed agg face do benefit from being compacted with a protected plate, but most standard pavers manage perfectly well without.