sandstone paving - expansion joint

[gsouth]

Hi all,

I am about to start a large paving job (have already completed a relatively small and easy one in the same area)

They are 600 x 400 sandstone pavers that will be laid into a mortar bed and then grouted.
The subform is an existing concrete slab which has expansion joints in it.
I know i have to continue the expansion joints up through the mortar bed and the pavers...

My question is what material do I use to fill the expansion joint afterwards so it looks good? They will be 10mm to match the grout lines.

Cheers
Geoff

[bricks]

At most building suppliers they have foam stuff its 100mm x 10mm and comes in 5m long rolls. Goes by lots of names ; aeroflex, melflex, builders foam, form foam, flat lagging.
Put this in between the pavers at the expansion joints, once you've finished paveing pull it out and youll have a 10mm slot which you then fill with construction caulking, that comes in tubes like silicone or bags like concrete and non-shrink grout.
Come to think of it that caulking gear might actually be non-shrink grout with a colour added????
The only gear i've used is an epoxy construction caulk Ill see if i can get the name of it and post back.

You could just leave the foam in there, ive seen that done also but its a direct entry for water under the paving.

[silentC]

If you want something waterproof, you can use Sikaflex Pro. It comes in various colours. You'll need a lot of it to fill a 10mm gap to the depth of a paver + mortar bed though. It's about $18 for a 310mil tube, or about $20 for a sausage (you need a special gun for it). There are other brands - it's a polyurethane sealer.

You can get bitumous expansion joint foam. That will keep the water out mostly. It only comes in black

Otherwise, I'd just use the standard foam stuff as mentioned above. If the expansion slot is self-draining (open at one end or both) then you wont have a problem.

[Bleedin Thumb]

Bricks I wouldn't go to so much trouble, if you pulled your expansion joint out you would then have to place a backing rod in the joint before gouting it. Bit of a waste of time and money.
Use AbleFlex foam in the thickness you need. the top then is designed to "Zip" off leaving you with a 10mm goove to grout if you wish.
If its a driveway I wouldn't bother but if it is a display area then perhaps.
What about your contol joints? are you going to continue those up through the paving.


Silent why would you need a waterproof joint - sandstone is very porous.

[silentC]

I don't think you do, just following on from our mate's advice that's all. If you want something waterproof, then Sikaflex is good. If you don't then use the foam. Just trying to be helpful

[Bleedin Thumb]

I think that the reason why Sikaflex and other silicon type sealers are used is not so much to seal the joint but to accept the expansion and contraction they get without failing.

That's why you wouldn't use a non-shrink grout in that situation.

IMHO its an overkill, I dont mind seeing the foam or even bitumous strip showing and I HATE applying silicon as I usually come unstuck or should I say stuck.
Having said that I can see that in some cases people will want their joints to blend in with the paving thats why you can get so many colours now.

[silentC]

I think that the reason why Sikaflex and other silicon type sealers are used is not so much to seal the joint but to accept the expansion and contraction they get without failing.

I actually believe it's both. If you want something that will seal the joint, you have to use something flexible. I believe that's the reason that products like Sikaflex have come onto the market. In the olden days you had to use mastic, which either stayed gooey and got dragged out and crap stuck to it, or it went hard and fell out. The new stuff is to address that problem.

As a matter of fact I used some on the weekend to seal an expansion join in a tiled floor. The tiler left the grout out for one row in the middle of the room. I bought a tube of Sikaflex Pro concrete grey. If you squint, it almost looks identical to the light grey grout.

[Bleedin Thumb]

Silent its a bit of a chicken/egg thing what comes first the expansion, adhesion or waterproof qualities? Doesn't matter really but for the waterproof qualities to be important the paving beside the joint must also be waterproof IE sealed tiles.

With sandstone on a mortar bed I'm not sure if the waterproof nature of the joint is important as the sandstone it is adhering to is wet anyway.

The joint has to be dry on application but I don't think that after its cured it matters if its waterproof or not.

[bricks]

That Able Flex is what I was talking about, i forgot a bout the top section but yeah, it goes by heaps of different names depending on where you buy it here in adelaide but in general it's the same gear.

The problems Ive seen with unsealed expansions are either, dirt and rubbish get in them and weeds beigin to grow or due to the large gap present, instead of a soaked state of the sandstone, you can errode the sub base of your paving through flowing water,
I've seen it done heaps of ways.

[joe greiner]

Ditto bricks' remark about crud buildup in an open joint. The rationale for the round backer rod is to provide a centre portion of sealant thin enough to stretch transverse to the joint, and sides thick enough for adequate purchase to the pavers or other parent material.

Joe

[gsouth]

Thanks for all your replies....
I don't want to leave the joint open - this is a "feature" area so we want it to look great.
I'll research some of the other products - I know the foam strips - although I did always wonder why there was a "zip away" section to them - now I know why )

Cheers
Geoff

[Bleedin Thumb]

Hi Geoff, you will have to place a stiff board behind your AbleFlex to get a nice straight line then work up to it - sorry if you already realised that.