Question re: vdw 840 plus minimum depth

Mr Potato · Post: # 105249Post **Mr Potato** Sat Jul 25, 2015 4:32 pm

Hi all,

I'm new to the forum and looking for some experienced advice. Please can you help?

The VDW 840 Plus tech spec PDF says the minimum joint depth is 30 mm.

I'm laying a slate patio which has flags around 18-22mm depth. If I was to be strict about following the guidance, then VDW 840 Plus is not an option. However, given that the patio will only be receiving very light and infrequent use by only a couple of people, can it still be used?

I'm happy with the product but this is the one point that prevents me from using it. Many patio slate slabs are around 20mm (ish) these days. Is VDW 840 Plus not an option by default?

The VDW 840 Plus tech spec can be downloaded here - https://www.nccstreetscape.co.uk/PDS....012.pdf and the minimum depth is mentioned on page 2 in the 2nd paragraph.

Thanks in advance for any feedback.

Mr Potato · Post: # 105250Post **Mr Potato** Sat Jul 25, 2015 5:28 pm

I've also found an article about VDW 840+ on pavingexpert.com http://www.pavingexpert.com/point_ncc02.htm that says, "The joints need to be empty (obviously!) and at least 20mm deep, roughly the depth of most of the imported patio flagstones in this country."

I guess my original question is just a belt and braces approach as the 20mm depth witnessed in the article is 10mm less than the recommended minimum depth of 30mm.

Has anyone used it on 20mm (ish) flags and had no issues or comebacks? Can anyone share their experience?

Thanks...

Post: # 105251Post **msh paving** Sat Jul 25, 2015 7:25 pm

i have used it on 20/25mm calibrated limestone no problems at all,just make sure no mortar is filling the joint and you will be fine, deeper the better but iv had no issues using it on calibrated slabs MSH

Mr Potato · Post: # 105253Post **Mr Potato** Sat Jul 25, 2015 9:59 pm

Thanks for the feedback Mark. It is appreciated.

Does anyone else have any experience and thoughts to share?

Post: # 105254Post **seanandruby** Sun Jul 26, 2015 7:56 am

If your that worried why not scrape out bedding between slabs an extra 10 ml ??? Personaly i'd be a bit sceptical about using something that can't be subjected to saturation. Another thought is that 30 ml recommendation means that your buying more of what they are selling :;): MSH has a good name on here and if he has used it at 20 / 25 ml then that is good enough for me.

Mr Potato · Post: # 105266Post **Mr Potato** Sun Jul 26, 2015 10:43 pm

Hi seanandruby,

Thanks for the comments. That's a good suggestion regarding scraping out the bedding between the slabs... thanks for that.

Not entirely sure what you meant by 'Personaly i'd be a bit sceptical about using something that can't be subjected to saturation.' Any chance you can elaborate bit more?

Thanks again seanandruby

Mon Jul 27, 2015 10:56 am

It's just my thoughts. Something that can't be subject to saturation being used where it will get, er' saturated

.
Was thinking that once it is all silted up then it will be permanently wet. I'm sure i'm overthinking it so best not worry.

Mr Potato · Post: # 105281Post **Mr Potato** Tue Jul 28, 2015 9:40 pm

Thanks seanandruby. I appreciate you taking the time to reply.

I think the summary is:

* 20/25mm should be ok.
* used at this depth without issue by experienced / respected forum member
* make sure no mortar is filling the joint in the first instance
* dig out the mortar if you wanted to create more depth, more than the 20mm

I spoke to NCC (distributor) off the back of my original post and your replies and they seemed happy enough at about 20mm+ minimum depth. They did suggest you could also have a slightly wider distance between the slabs for additional volume if that was your concern. They also pointed me in the direction of the vdw 800 which they described as a step up in performance compared to the vdw 840 plus and what they would have on their patio if they were doing the job. Although at Â£80.47 for a 25kg bag and Â£564.56 for 200kgs at the time of this posting... I can also understand why!

Thanks again everyone. I hope this helps others in the future as well...

Mr Potato

Post: # 105325Post **Tony McC** Thu Jul 30, 2015 7:12 pm

GftK and their UK distributor, NCC Streetscape, have to be all 'belt-and-braces' with their specs, and you have to bear in mind that it's in their interest for you to use more of their product.

Meanwhile, in the real world, I've seen tens of thousands of square metres of 28-25mm Indian stone jointed with the 840, the 800 and the 850, and never a problem as long as there is a minimum 20mm depth on non-trafficked areas.

And for my money, the few quid extra you pay for upgrading to the 800 or the new 850+ is very definitely worth it. A 2-part resin is nearly always superior to a polymeric, even a polymeric as good as 840!