Forum: Flags and Slabs
Topic: Granite planks
started by: Bob_A

Posted by Bob_A on 01 Oct. 2019,20:59
Well the missus idea of circle kits last all of 5 minutes and now the boss wants the complete opposite being granite planks 900x200x20 for an area of 15m2 where next doors Leylandii drops it bits.
I'll probably be using GFTK or Romex for the jointing and would like the joints to be narrow, how narrow can I safely go, I was hoping to go for 5mm.

There are a number of GFTK usage calculators on the web but only when I use this one I get a message saying 'joint depth should be more than depth 30mm
< LINK >
I do not get this warning on the manufacturers website
< LINK > assuming the manufacturer should know best is it safe to assume 5mm wide 20mm deep joints be ok?

Posted by Tony McC on 04 Oct. 2019,09:20
If you use the VDW 815, that's designed for 3-5mm joints, so ideal for the sort of joint you are considering.

The 30mm depth requirement is "up for discussion", shall we say. There does need to be a minimum depth, and that is probably at least 20mm. Then there's a depth at which possible failure is pretty unlikely, and that's probably closer to 25mm. And finally, there's a depth at which failure almost never happens and the supplier gets to flog lots of lovely mortar. This all gets a little complicated by the fact that the 815 is designed for narrow joints, so, while the VDW 850 at 10mm width may well last for decades at 20mm depth, with just 5mm or so of the 815, some additional depth is necessary to give the material enough 'bant' to survive.

With these planks of yours, I'd lay as directed (and be aware that some granites really need to be pre-sealed), then rake through the joints with a big nail to give a bit of additional depth and clear out any accidental debris. This should give you 20-25mm depth, and that would probably be adequate for a residential patio.

Posted by Bob_A on 04 Oct. 2019,11:58
Thanks Tony and you also managed to answer a question that I had thought about but haven't asked yet.
The answer is a big nail :laugh:

Posted by Tony McC on 07 Oct. 2019,09:05
Invaluable bit of kit, is a big nail! :D
Posted by Bob_A on 18 Oct. 2019,22:27
Iím thinking about using my cheap and nasty table saw < IT'S THIS ONE > and replacing the blade with a diamond one to cut my granite planks.For my project I will need to make a total of approx. 20 cuts each 200mm long into the 20mm thick granite planks, I would be looking to buy a cheap blade so it can be discarded afterwards † I assume I can do this?
The bore of the blade needs to be 25.4mm which really cuts down the amount that are readily available, if it were 22.2mm then theyíd loads to choose from.
Most blades with a bore of 25.4mm have continuous rims, very few have segmented edges. Will a continuous edge blade be ok
If the table saw gets ruined in the process then it's not a problem, it'll be an excuse to replace it :laugh:

Posted by dig dug dan on 20 Oct. 2019,08:51
How will you apply water?
Posted by Bob_A on 20 Oct. 2019,10:20
I was going to very carefully tip some water out of a cup as I went along or better still get an assistant to do it. The machine will be protected by an earth leakage breaker.
I know I'm talking about making twenty 200mm cuts into granite but I got the idea of a table saw from this porcelain thread
< Link >
I assumed the table saw mentioned in that thread is an ordinary general purpose one? I'd imagine it would need to be kept clean all the time but that's only time and I have plenty of that.
Could I get away without using water if I can get hold of a segmented blade, I know dry cutting is frowned upon but if I'm the only one in my garden and I'm wearing PPE perhaps I could be forgiven for the small amount of cutting I need to do?

Or maybe a tile cutter for this one off job and if it survives I could always use it as intended a tile cutter.
< This one looks less plastic than the other cheapies >

Posted by Tony McC on 22 Oct. 2019,12:29
I'm by no stretch of the imagination an expert on saw blades, but somewhere in the back of me mind is a remembrance that cont. rim blades *must* be cooled, whereas segmented blades are better if cooled, but it's not quite essential.

I'd be loath to cut granite without cooling - it eats blades is they are allowed to get too hot.

Posted by Bob_A on 22 Oct. 2019,14:16
Quote (Tony McC @ 22 Oct. 2019,12:29)
I'm by no stretch of the imagination an expert on saw blades, but somewhere in the back of me mind is a remembrance that cont. rim blades *must* be cooled, whereas segmented blades are better if cooled, but it's not quite essential.

I'd be loath to cut granite without cooling - it eats blades is they are allowed to get too hot.

Thanks Tony I've got my eye on a 650w (rather than the cheapest 450w) tile cutter table that's water cooled. Maybe buy a segmented blade and together with the water it might just do it  
If not I still have a tile cutter for an indoor project in the future :D

Posted by Bob_A on 23 Oct. 2019,19:17
I've started and making good progress with the sub base, I'm using 75mm of type 1.
Although it's probably not necessary I've put a geo textile between the sub grade and sub base, reason being is I got it dirt cheap.
My standard bedding layer will be 6:1
Laying to a free edge will be like this

To finish the fabric at the edge I was going to bring it upwards fold it back and sandwich it between the sub base and the Class II, if that's ok does it matter how much I fold back and sandwich, just wondering if it can be too little or too much that it could compromise the job the Class II is meant to do.
Thanks †:)

Posted by lutonlagerlout on 24 Oct. 2019,17:19
Hi Bob
what kind of granite are you using?
cheers LLL :)

Posted by Tony McC on 24 Oct. 2019,19:24
Bob - no problem with your proposal.

Possibly pre-empting what's going through the mind of LLL, but don't forget to use a good quality < slurry primer bond bridge > on the underside of the granite flags immediately before laying.

Posted by Bob_A on 25 Oct. 2019,00:34
I always do a fair bit of research on here and read that you have reservations about Chinese granite, you being a regular I always take note and for that reason I recently resurrected an old thread to find out more< Link >
As you've pointed out some granites are prone to reflective staining, mine is an Indian †granite and I'm going to take Tony's advice and use a slurry on the underside which will hopefully negate the effect. Fingers crossed :D
I may seal it from the top but will wait until the dryer weather next year before deciding.

Tony McC
The planks have a depth of 200mm so I was going to dampen the fabric, fold it back so that 75-100mm is left under the planks, ClassII and finally lay the plank with the slurry applied.

Posted by Bob_A on 08 Nov. 2019,20:14
Most of the granite planks are down so itís time to think about VDW815. It says the minimum working temp is 3C. Iíll check with the Met Office but achieving above 3C during the day in London is not normally difficult but what about if it gets unexpectedly frosty overnight, will that cause problems? The first thing that comes to mind is to cover the newly jointed patio overnight, Iíve got a thin tarpaulin, will that do? Donít really want to buy something just for a night when it might not even drop below 3C.
Will a cheap tarp be adequate?

Posted by Tony McC on 10 Nov. 2019,09:34
It really is important to observe temp requirements. It's best to wait for a suitable day, which I acknowledge are fewer and further between just now, but if it means holding on for a few days, it's well worth the delay.

Tarps work fairly well, but you can improve their effectiveness by scattering the surface with straw or scrunched-up newspaper/carboard before covering with the tarp - that traps in more of the insulating air and keeps it still.

Posted by Bob_A on 10 Nov. 2019,10:26
Quote (Tony McC @ 10 Nov. 2019,09:34)
......if it means holding on for a few days, it's well worth the delay.

Now that that the days are shorter the plank laying seems to be taking ages, I'm hoping to finish today. The missus bless her can't wait as she wants to do some gardening around that area but I will take your advice and wait for a favourable day for the VDW  :D
Posted by Bob_A on 12 Nov. 2019,23:04
Have been doing some research and been looking at videos for VDW815 including < THIS ONE >

My new patio isnít that big and measures 5m X 3.2m and according to online calculators I need around 20Kg so to be sure Iíll be buying 3x !0Kg tubs.

I was going divide the area into 3.
With the first tub I was going to fill the joints in section 1, move any excess into section 2, add the second tub, fill the joints, move any excess into section 3, add tub 3 (if necessary) fill the joints and remove excess.
Finally use a broom to brush away any remnants from the whole patio.
All done with copious amounts of water. Is that the right way?

I get the message that you canít use too much water, but Iím still concerned, isnít it possible to actually wash the product out of the joints or brush too much away †when using a soft broom? It sounds too good to be true.

Sorry if Iím making a meal out of this but this stuff ainít cheap and I donít want to **** it up †:laugh:

Posted by Tony McC on 14 Nov. 2019,10:01
It's surprising how heavily this mortar sits in the joints, once you get it in there.

For such a relatively small area, Bob, I would mix two of the tubes in one go, put them in a bigger bucket, if necxessary....or look at getting a single 25kg bucket (if they do one!)

Soak the whole pavement, soak it for at least 5-10 mins, so that there is standing water on the surface, and then tip out the mixed mortar, spray it with more water as you brush or squeegee it over trhe whole surface, NOT just the joints, and then, when they seem fairly full, keep on spraying but give it 5 mins or so to settle. Then start to sweep off, still spraying as you go.

If you need that third tub, use it now, while the first two are still fresh in the joints. Same procedure as above.

If you sweep on the diagional, so at 45į to the joints, very little will come out of the joints. Once you have most of the surplus brushed off, stop with the water spray but keep brushing. You can tool the joints if you wish, but I don't think this really achieves anything (unlike with cement mortars, where it most definitely does harden the surface).

You'll find it far easier than you expect. The two key things to bear in miond ios loads of water before and during, then loads of brushing after, to ensure nothing remains on teh surface.

Looking forward to hearing how you get on......

Posted by Bob_A on 14 Nov. 2019,21:05
Thank you for that excellent explanation that really has boosted my confidence

Posted by Bob_A on 20 Nov. 2019,11:07
As regards the VDW815 Iíve got to admit I struggled to the point that half way through pointing I rang Carl at NCC for advice. The advice he gave me was to no surprise virtually the same as what Tony had said so it must be me. :p
I flooded the area with water, tipped out the compound and started to squeegee it in with the hose going, the problem was getting the compound into the waterlogged joints, after a while the level of compound in some of the joints had dropped and needed topping up (where I assume the water had finally seeped away?) †it was taking so long that the last bit of compound of the 2nd tub was going off and needed to be discarded. To finish the job I opened the 3rd tub, I didnít need all of it and ended up for the last bit of the job forcing the compound into the joints with a trowel rather than squeegee it. It was almost as if the compound was having problems dispersing the water out of the joints, when I spoke to Carl he said perhaps I didnít use enough water throughout the work but I certainly had the hose on almost constantly. †
The only logic I can come up with is that the joints were full of water and the compound even though it is heavier it still found it difficult to disperse the water in joints.
Anyway I got there in the end and itís probably me and user error but many thanks to Carl for taking my calls and putting me at ease. Heís doing a demonstration in the south east and heís going to send me an invite.

So apart from the area around the patio that needs to be done itís finished.
Thank you for the help it's much appreciated:D

Posted by Tony McC on 20 Nov. 2019,13:45
That looks spot on, Bob, despite your struggles.

I suppose it's all too easy for us so-called professionals to assume particular taks are stunningly simple, when we're doing them every day, but for those doing it perhaps only once in a lifetime, it can be quite daunting, but you've shown that it *is* possible and the results can be just as good, if not better, than those achieved by a professional.

Carl is a good lad and I'm sure you'll benefit from chatting with him at the demo day.

Posted by Bob_A on 20 Nov. 2019,15:31
Good man is Carl he was at Futurescope when I called and he still took my calls. Perhaps you bumped into him yesterday.
Big thanks for your help along the way Tony and to your main website which I constantly refer to.

Oh by the way I cut the planks with one of< these >
I replaced the continuous blade that came with it with ones of < these cheap segmented > then elongated the left and right sides of the machine with some wooden extensions so that planks were fully supported when cut. Of course that wouldn't last 5 minutes in the hands of a professional but thought it worth mentioning as an idea for fellow DIYers :D

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