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Posted: Fri Aug 28, 2015 11:41 am
by Hammer80
Apologies for another question on sealants…

We had a light, sawn Indian sandstone patio laid a little over three years ago. It’s around 100 square metres and has fairly narrow joints (rough average 6mm) – it looks like many of the ‘contemporary’ patios in the brochures.

After a couple of years of cycling through it going deep green, jetwashing, using chlorine etc., last summer we decided to bite the bullet and get it sealed. I had a good look through these forums (thanks for all your very helpful posts!) and decided we ought to do it properly, so I had Dry Treat Stainproof applied by a Dry Treat-accredited contractor.

The Dry-Treat has generally been good on the stone. However, one problem I (and the contractor) hadn't been prepared for was that the Dry-Treat hasn't had much effect on the porosity of the joints.

Unfortunately the joints were done with one of the one-part polymerics (Sika Pavefix I believe.) Although the joints were treated with plenty of the Dry-Treat, other than in one or two places they’re still extremely porous – I guess that even once cured, the structure of the polymeric just isn’t dense enough for Dry-Treat to work with. In places the joints have also shrunk slightly and come away from the sides of the stones, which I understand is fairly normal.

When it rains, the joints become completely saturated and can take days to dry out fully. They look pretty ugly while wet/drying; the constant dampness means that they quickly go green/black; I’m concerned that if we have a heavy winter they’ll just fall apart; and last but not least, in a few places the stone is still going deep green around the edges of the joints as dampness seeps through despite the Dry-Treat.

Obviously the correct response would be to grind the joints out and re-do with something better, and I certainly hope to get someone in to do that in a year or two, but it’s not really possible right now.

The reason for this post is that I’m considering going over the joints with a topical sealant to waterproof them.

Although not ideal, this should at least be relatively quick, I can do it myself, and it shouldn’t cost the earth… I have a couple of sealant samples from Resiblock to test out when the weather improves. I'll try painting the sealant over the joints with a brush, making sure the coat goes up to the edge of the stone (possibly easier said than done.)

My question is… does this sound like a good idea? Is it pure idiocy?

Any thoughts or experiences would be very gratefully received.

Thanks!

Posted: Sat Aug 29, 2015 8:53 pm
by London Stone Paving
I dont think what you are proposing will Have the desired effect

Topical sealants are designed to fill the microscopic pores found in natural stones. The cappillaries in a polymer joint are going to be many times greater than stone.

Your time would be better of spent doing the job properly and replacing the jointing material if you can't live with the algae

Steve

Posted: Mon Aug 31, 2015 8:52 am
by Hammer80
Hi Steve, thanks for the advice - much appreciated.

I see, makes sense. I guess I'd been thinking of the topical sealant as being akin to a coat of varnish rather than something that would properly bond into the stone.

Yes, I agree it'd be better to do the job properly and re-do the joints, it's just that I'm not confident doing that myself so would need to get someone in. I'd much rather have the VDW 850 or the GPM as per your website (we have your beige sawn sandstone) but our original landscaper only wants to use the one-part polymerics - and I can understand why from his point of view. People I've spoken to generally seem to want to use the one-parts.

Guess I'll need to live with it for now and call around other contractors when I can face it!

Cheers

Posted: Mon Aug 31, 2015 11:09 am
by London Stone Paving
I cant understand why a landscaper would have any apprehension about using a 2 part.

All you need is a drill and a paddle. The mixing is done within the GFTK tub, couldn't be any easier really.

The biggest hassle is the grinding out of the old material and taking care not to nick the edges of the slabs with the grinder.

If you need me to recommend a contractor I would be happy to do so

Steve

Posted: Wed Sep 02, 2015 12:08 am
by Hammer80
Cheers Steve, will send you a PM

Posted: Mon Sep 14, 2015 7:36 am
by GGG
Interestingly I have found the same with all the impregnators I have used, so I am now using Resiblocks Indian Sandstone Enhancer (on all my natural paving). I have been using it for 6 months and now and don't seem to be having any issues and it really does appear to do the trick on sealing polymer modified mortar joints as well.

When I asked them about a similar job to yours they said say they have limited experience going over other companies impregnators and such (as much as they would like the sale!) they couldn’t recommend it. Apparently their material is for untreated paving only.

Guessing I’m not helping much.....
GGG