Sm water feature, securing granite blocks onto pond liner?

[Deansplit]

I need to know what you use to secure small (100x100mm) granite blocks on top of pond liner.

I've not made it easy for myself!!

See pics, ignore the plants!... the pond liner will lip over the lead flashing and I want to have the granite blocks around the top, ie. on the liner to 1. secure it, 2. finish it off. Whatever I use needs to be waterproof as the water level will be half way up the blocks. I know it's not ideal building with these smooth faced blocks like this, they're meant for laying on the ground, but I'm sure there'll be a way of doing it...?

I imagined I'd do it like this unless any better suggestions:

Lay in the liner first, fill it so the liner pulls down to the bottom of the well/water area and then I'd pull and lay it over the glass blocks and cut it just short of the front edge. The lead flashing bridges a cavity where rope lights will be so glass block illuminate. Then lay a bed of mortar (that's what I'm asking to use for this??) and sit the blocks around the top like a coping. As long as the mortar is the right consistency, it hold between them ok as I did this on the base, that was normal sand & cement.

Any suggestions...?

Thanks

Untitled

• Deansplit
• 14 Jun 2014
• 1

Untitled

• Deansplit
• 14 Jun 2014
• 1

 

[r896neo]

So you will be laying the blocks on the liner but then having the water level half-way up the blocks? You would be better off building it with normal mortar and then painting the back with a liquid dpm or if your having fish or plants in the water use a pond paint.

No normal mortar will tolerate constant saturation with water without bad staining and deterioration.

because there will no no weight on top of the granite the secret will be to have the mortar as one continuous bed to give it weight. A good strong 3:1 mortar

3 plastering sand: 1 cement and some SBR to help it bond to the granite.

The other option is to put in a bed of mortar and then lay your blocks onto it with tile cement as it will bond them better.

Trying to keep it all as one well bonded mass will give it the best chance of survival.

 

[Deansplit]

Thanks r896neo, yes you have it right with the water half or some way up the back side of the blocks. Ideally I'd love to finish the top of the blocks with something more decorative as you'll see the mortar joint... no idea what though!

Cheers

 

[Deansplit]

Hey, r896neo, was wondering if you could advise if you may know...

You mentioned SBR for adhering to the granite block. For the amount I need I'll have to buy 5L! I just remembered, we had a gable wall stripped and tanked – I have some left over, the builders left it here, it's called Triton TT55, see here, sounds very similar http://www.tritonsystems.co.uk/pdf/Triton_TT55_DS.pdf

Do you think this would suffice?

 

[r896neo]

No that won't help but brilliantly that is the perfect stuff to paint the back of your granite blocks and mortar with to stop staining caused by saturation. You can apply it with a brush to any masonary below the water line.

If you dont want to go with the sbr then prime the blocks a few mins before laying with a gloopy cement slurry made up of 2 parts cement to 1 part sand and enough water to make it the consistancy of yogurt. Then paint it on. beware it will stain so dont use it in any visible area.