The Brew Cabin

Posted: **Sat Jul 31, 2010 1:23 am**

I'll shortly be laying some lovely sandstone slabs (ok- tiles) for a large patio area (DIY job, I'm not a pro, yet

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The tiles are 22mm sawn, polished sandstone with a ribbed underside to aid bedding in. They have perfectly flat tops and are completely uniform thickness, even between pallets.

NOTE:this is on top of a 75-100mm Type1, compacted and adjusted to correct levels/gradients etc- its just the laying part I need advice on.

Heres what I plan to do (feel free to criticise- please)...

-Use a 5:1 sharp sand/cement mortar (damp/moist mix)

-Lightly compact semi dry mortar (with feet).

-Screed compacted mortar to correct level (40-50mm deep)

-lightly scarify top 5-10mm (with some medieval looking, home made rake of nails) to give tile something to settle into.

-Lay slab on top and gently tap into place with appropriate tool.

-Wait at least 48hr, then mortar up the joints.

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Right- any of that sounds iffy- please let me know.

In addition...

Adding waterproofer to bedding mortar? I heard this prevents that nasty white crap seeping up from type1 and depositing on slabs/mortar joints. Worth doing or nonsense?

Adding some builders sand to the mix to help it snuggle into those wee grooves under the tile? Could that cause any problems?

Finally- I'm keen on the idea of painting some cement paste onto the bottom of the tile to aid adhesion. Any details on what to make it up with (SBR? How thin a paste we talking? Ive never seen that done so any advice would be great.

Thanks again guys- sorry to prattle on so much. Just dont wanna fall on the last hurdle!

-Michael

Posted: **Sat Jul 31, 2010 8:27 am**

your technique sound like you have read the main site Michael well done!
the suitable tool you speak off is a rubber mallet and you need to paint a slurry of 1:1 sbr : neat cement on the underside of your flags to make the bond bridge
ideally you will use some electrical ducting 18 or 25 mm to use as screed bars
but try and use a line to lay the actual flags
any more questions ask away
LLL

Posted: **Sat Jul 31, 2010 12:48 pm**

lutonlagerlout wrote:...sound like you have read the main site Michael well done!

Every page and every word! Absolute goldmine of info! Thanks.

Anyways- looking at SBR at screwfix. Can I use this one...

Cementone Â£15.99 /5L
or do I need to use this one...
Mapei Planecrite Â£28.99 /5L

How many (roughly) do you think I'll need for around 40m2?

What about adding some to mortar as waterproofer (to prevent white stuff leeching up?

Thanks again.

-Michael

Posted: **Sat Jul 31, 2010 1:53 pm**

pcdoc wrote:
lutonlagerlout wrote:...sound like you have read the main site Michael well done!

Every page and every word! Absolute goldmine of info! Thanks.

Anyways- looking at SBR at screwfix. Can I use this one...

Cementone Â£15.99 /5L
or do I need to use this one...
Mapei Planecrite Â£28.99 /5L

How many (roughly) do you think I'll need for around 40m2?

What about adding some to mortar as waterproofer (to prevent white stuff leeching up?

Thanks again.

-Michael

cemstone sbr is fine 5 litres okay try bq may be cheaper but they should price match bq cheapest for cement 5 or more bags good luck your on the right track ask if you need help or unsure or you can call me cheers cookie :p

Posted: **Sat Jul 31, 2010 2:23 pm**

pcdoc wrote:-lightly scarify top 5-10mm (with some medieval looking, home made rake of nails) to give tile something to settle into.

This a good diy tool
http://ext.pavingexpert.com/cgi-bin....hl=rake

Posted: **Sat Jul 31, 2010 3:39 pm**

i just laid 150m2 of the 22mm sawn stone, just normal mix 5:1:1 sharp sand, building sand, cement. i like a bit of sand in there makes it slightly smoother

then added SBR directly into the mix and bedded as per usual, laid bed with shovel for each flag then tapped to consolidate and level

worked a treat but you need a bit of the knack to get the bed the right thickness each time

Posted: **Sat Jul 31, 2010 5:31 pm**

Thanks for all your answers- its appreciated.

GB_Groundworks- I will deffo be adding some building sand, my grit sand does seem to be slightly higher in grit than Id like.

Cementone SBR it is then at Â£15/5L.

I think mixing SBR directly into the mortar sounds like the way to go. I want to avoid any white efflorecence and that should help.

Did you still paint SBR onto undersides? Bit worried about messy handprints on the slab face doing that.

How much SBR is added to mortar? Is it about 100ml per 25kg bag of cement, similar to plasticisers? Just trying to gauge how much to buy in.

Thanks again.

-Michael.

Posted: **Sun Aug 01, 2010 8:35 am**

bear in mind pcdoc that efflorescence is something that sometimes occurs, but is hard to reproduce,personally i have never seen it with natural stone
SBR is very sticky avoid contact with skin at all costs
LLL

The Brew Cabin

Laying sawn sandstone on screed bed. - Need some tips, please.