Mortar joints - slabs

[Soni]

Hi, this is my first post!

I laid a patio of 200 slabs around 5 years ago when i first moved into the house i own now.

I was very pleased with the outcome, it was perfectly level on a spirit level, no rocking slabs, and i was just so proud that i had accomplished it.

However, when it came to mortaring the joints, i wished i never bothered.

I read on another website that to mortar the joints, knock up some wet concrete and tip if over the patio and brush it into the joints with a broom.

This i did, around 9 aclock at night in the summer, it was just about getting dark, and i hosed it down afterwards to remove all the excess mortar - or at least i thought i had!

The following morning when i awoke, i went straight outside to see the lovely job i had done, and was shocked to see the look of the slabs. I was truely gutted, every single slab had staining on it, i thought i would be able to clean them up, so purchased an acid based solution that bricklayers apparently used to clean their tools, and poured that over the slabs and used a scouring brush to scrub the slabs.

My wife and i spent around 4 evenings in the garden trying to slean the slabs up, and although we managed to get the majority of the mortar off the slabs, the slabs were ruined.

It had taken the nice sandstone finish off the slabs, and we were left with a grey/white looking plain concrete finish - i can't explain in words the way i felt, after doing such a good job at laying the patio, and then ruining it completely - i felt like jumping off a cliff, and that is no exageration.

Sorry for the long post above - but as you can imagine, i'm very paranoid now about mortaring paving slab joints.

I have just had a conservatory built on the previous patio site, so decided it would now be the perfect opportunity and time (summer approaching) to lay another patio.

This time i have dug down 2ft for the foundation for the patio (as had some garden subsidence - won't bother going into that now) and laid 2ft of Type 1 MOT Roadstone wnad whackerplated it for the base, and have just laid 200 slabs onto a sand/cement screed.

I'm very happy with the result, better than before, and have made sure that any concrete dust that gets onto the slabs is brushed off immediately!!

However i'm now nearly ready for the mortaring again.

My question is what is the correct way to mortar the joints?

I have laid sandstone/yellow looking conrete slabs with a ripple effect, i would ideally like the very white looking concrete looking mortar effect that you see that have an edge on each side?

[Rich H]

There's a lot of information on the main site about pointing, but the main concerns I have from your post are this:

"This time i have dug down 2ft for the foundation for the patio (as had some garden subsidence - won't bother going into that now) and laid 2ft of Type 1 MOT Roadstone wnad whackerplated it for the base, and have just laid 200 slabs onto a sand/cement screed."

A wacker cannot compact 2ft of Type 1. Perhaps you're just explaining in shorthand but you would have had to have done no more that 100mm at a time to get full compaction or better still hardcore and readymix concrete to fill that kind of hole.

Secondly, "I read on another website that to mortar the joints, knock up some wet concrete and tip if over the patio and brush it into the joints with a broom."

You can do this with dry mix but not wet. Your best bet is to get yourself a good quality jointing trowel or pointing tool, knock up the mix, pile it around the joints of first slab and work it in really well with the tool. Once finished with the first slab, brush the excess to the next joint, supplement with more mix and repeat. If you're doing it properly the mix should be quite fine but moist enough to stick together if you mould it between your hands. It should take you all day to do 200 slabs if you're working it in well. If the day is hot and sunny watch out for it drying out before it cures; you might have to mist it with a fine spray section by section as you go.

That's me, and different pavers have different methods. Best bet is to read all of Tony's advice for best practise in laying slabs and pointing.

[Soni]

Hi Rich, thanks for your reply.

Yes i was being a little vague with my description of my patio foundation, this is what i did.

I dug down around 24", removed all the soil and loose hardcore to the front garden.

I then sorted out all the decent quality hardcore, broke it up into small pieces, then relaid it back into the ground, i then ran a whacker plate over it for around an hour, then i poured a bit of type 1 mot roadstone over the hardcore, then whackered that - it then went solid like tarmac!

I then kept adding the roadstone a bit at a time, and then re-whackered it, and then left it for a couple of weeks until i got the slabs and sand/cement delivered, by which time it had been walked over quite a bit!!

I then started laying a bed of sand/cement (4:1) and laid one slab at a time.

I've just got to get rid of a whole front gardens worth of soil and wood now - any suggestions on the cheapest method?

[bobhughes]

Soni
Be worth investigating a self loading tipper (one with a grab on a crane). Not much more than a skip and a hell of a lot less work.

Bob

[Soni]

Soni
Be worth investigating a self loading tipper (one with a grab on a crane). Not much more than a skip and a hell of a lot less work.

Bob

Hi Bob,

I phoned about a grab lorry, and they wanted to charge me around £170.00 for the hardcore and soil, but i've also got a lot of wood, and they said it would be nearly double if i want the wood taken away as well.,

[Soni]

I've just laid some more slabs tonight, and was rushing as it was getting dark.

I was measuring with the spirit level whilst i was going, but i obviously couldn't see too well in the dark.

My patio is accurate (bubble equally between both inside lines) for over 3 quarters of the patio, however the area i've done this evening (around 16 slabs) is slightly out.

The bubble is just touching the inside line on a couple of runs and its really annoying me. It doesn't notice to the naked eye, but the fact that its touching one of the inside lines going accross at the end of my run is really annoying me, as the rest is 'bubble perfect'.

They are rippled slabs, but i've even laid a straight piece of wood around 5 feet long over the area i've done tonight, and its still showing as the bubble touching one of the inside lines.

Would you guys recommend i take them back up and relay them?

[lutonlagerlout]

am i being thick but you NEVER lay a patio level?
where will the water go when it rains
most patios i lay the bubble will nearly be touching the line on one side
remember the slabbers motto
"lay in haste,repeat at your leisure"
cheers LLL

[Soni]

am i being thick but you NEVER lay a patio level?
where will the water go when it rains
most patios i lay the bubble will nearly be touching the line on one side
remember the slabbers motto
"lay in haste,repeat at your leisure"
cheers LLL

I ripped the slabs i laid last night up this morning at 05:30 and re-laid them before going to work

I understand what you're saying about a patio not being level due to water drainage, however i have allowed a slight decline with the bubble touching one line towards the garden, which will hopefully be enough for water drainage, however what i WAS worried about last night was the bubble was toucing one of the lines going accross the patio i.e., i allready have a slight fall towards the garden, however the slabs i laid last night had the bubble touching one of the lines going accross the patio.

As i say, i've now relaid the slabs this morning, and they are spot on going accross ways, bubble smack bang in the middle, however i haven't got the same fall on them as i have on the rest of the patio, although the slabs at the far side of the patio are now dead straight, the fall seems to have gone completely i.e., the bubble is either bang on in the centre, or its edging towards the other end of the bubble line

Although, they are riven/rippled effect surface slabs, so i imagine it could be something to do with the ripple pattern/protrutions on the slab surface which is causing this....

[Rich H]

If you're laying any kind of riven slabs you need a long level, preferably a 6' one. If you use a small level slab-by-slab it's easy to drift off, even if the bubble 'looks' bang on, it might be fractionally off.

Whatever you do, don't have ANY slabs level in both directions. Water will stand, moss, etc., will grow and it will look awful.

[lutonlagerlout]

i use a line for riven slabs ,you cannot trust levels on these yokes
just use the line and take the median point trying to avoid trip hazards
cheers LLL