Blocks not adhering with cement

Hi all

The BBQ project is progressing with the main structure built. I am now building the chimney bit which involves laying a course of cut down blocks (90mm high) 30mm overhanging the row below. After a lot of messing around I seem to get it going and laid 2 rows. As I only had a small amount of time I ended up laying them on different days.

I looked at them last night accidentally knocked it slightly and noticed that the entire first row wasn't adhered to the main structure below. Now when I did row 2 I checked row 1 and it seemed fixed ok. I have now removed both rows and will have another go tonight.

So the question is what did I do wrong? Some may remember that I had issues with the cement drying out far too quickly so my bodged technique has been

1. Soak the blocks in some water so they are wet when used
2. Put the mortar in a lidded plastic container and use as needed from there
3. Wet the row of blocks below before adding the cement
4. For these rows the overhang edge kept dropping so I used some 10 mm spacers to hold them up then remove and fill gap a few hours later

Any suggestions?

Thanks

Lee.

What kind of blocks? (lightweight ones are quite difficult to stick to anything!)

Fresh mortar, paint the block's mating surface with a mix of water and SBR prior to laying. (or water and waterproof PVA).

Mmm yes they are lightweight blocks. Sounds like that's not a good idea? The mortar is fresh as I only make enough for 4 blocks at a time 😃

I might have some old SBR in the shed will take a look. Do I let the SBR / PVA mix dry first or lay it when wet? I will draw a diagram of what I am trying to achieve and post it a bit later.

Thanks for your help

Lee.

They are ok, but usually work best upright and in compression. Can be hard to render onto though without a layer of EML.

That might be a bit excessive... :-)

Lay it when wet or tacky, don't let it dry.

Thanks John. As promised this is a link to a couple of photos showing what I am trying to achieve.

Given the overall height and size of the total overhang, is this going to work if I can get the blocks to work?

Checked the shed and no SBR or PVA so need to source a small tub of it somehow.

Thanks

Lee.

Everyone knows mortar holds bricks apart, not stick them together.

Unless you want to re-use the bricks, then it sticks like Witney to a blanket!

If you go down any street with walls with coping stones on them, odds are that at least 1 third are loose after a few weeks. Brian