Pointing a Patio -

[K-Rod]

Hi everyone,

Firstly apologies for posting yet another thread on patio pointing, however I spent a good hour last night reading the results of a search and am now even more confused than before I started, hence this post.

As a bit of background I'm in the process of laying a 25m squared patio. It's sat on 50mm crusher run and 50mm sharp sand, both compacted well. The slabs are 450x450x35 and 600x600x35 grey textured slabs from B&Q and are being laid in a "Dutch" pattern. They are separated by 10mm dowling to get an even joint. I've uploaded a photo which should give you a rough idea.

Untitled

• K-Rod
• 14 Apr 2009
• 1

The problem I now have is I'm not sure exactly on the correct, or best way to point between the slabs. I was intending on brushing a dry mix between the slabs and leaving nature to take it's cause and set the mixture, however, after reading a number of posts on the subject it seems that this method may not be suitable and even frowned upon a little by you experts.

I'm still currently leaning towards a dry mix but what is the best ratio? I've read 3/1, 4/1 and even 10/1. Some brush and leave and some seem to compact it down with a piece of wood, copper pipe etc etc? I've also heard the term "strike" - what does this mean?

So, my question to you all is "What would be the best method of pointing to give me the best results"?

I'm by no means an expert DIYer but I'll give most things a good crack - this is my first patio (please don't say you can tell )

Any help you can give me will be invaluable.

 

[noseall]

I'm afraid that you have fell foul of diy ignorance.

Slabs should be laid on a solid bed of sharp sand mortar. For best results and one that will last longest, you are best forming a joint as you go. This is done by teasing some of the mortar onto the edge of the slab prior to laying the next neighbouring slab.

It is the same principal as bricklaying. You would never see a bricky point mortar into empty perps! By teasing the mortar up the side of the slab, the jointing mortar and bed mortar are knitted together as one. SOLID.

In poor weather however, common sense says leave the joints empty as rain can spoil the party. In this instance pointing with mortar is inevitable.

Laying slabs on a dry sand bed and brushing in dry mix pointing is the easiest and poorest way you can lay slabs. Sorry.

 

[noseall]

Striking a joint means running a gagmush (jointing iron) or a pointing trowel across the joints once the mortar has stiffened a little.

This compresses the mortar pointing and provided a tight weathering surface to the pointed joints.

 

[K-Rod]

Thanks for the replies Noseall. Not the response I was hoping for but.....

I did read up extensively before I started this project, mainly on Paving Expert where it does state flags can be laid directly onto sand - http://www.pavingexpert.com/layflag3.htm#bornb. The area will only have light people traffic.

However, I can obviously see how a mortar bed would be more solid.

In your opinion, would you recommend I take up the flags already laid and start again using mortar?? I've done about 1/3 of the patio so it's not like I've almost finished it

Is the mortar laid directly onto the bedding layer of sharp sand?

 

[Thermo]

have to agree with noseall. slabs that are normally laid on a compacted bed are normally butt jointed, so the pointing isnt an issue. Laying on compacted sand gives a flexible paved area, that means it moves slihtly and the pointing will crack up.

I would relay them on a solid bed now. They can be easily pointed after or as you go, the mix needs to be damp enough to mould in your hand, without any excess water draining from it, or any marking your hand. you can then work this into the joint. The best method is a long peice of feather edge board to do this, so it is compacted well down into the joint. It can then be struck, ie finished off as you want it for the pointing effect to compliment your slabs.

 

[K-Rod]

Thanks Thermo.

Quick couple of questions.

If, hyperthetically, I leave the slabs on sand and point them with a brushed in dry mix - how long would you estimate the pointing would stay intact? (worst case scenario)

Is it a 3:1 ratio of sharp sand to cement I use for the mortar bed and does this go straight on top of the compacted 50mm sharp sand bedding layer?

Thanks.

 

[Thermo]

about 3-6 months if youre lucky.

If youre going to relay it, take up the slabs, and shovel up the sharp sand and re-use if for the mortar. when you bed them down, dont do a dob in each corner and the middle.

 

[K-Rod]

Cheers Thermo.

I think I'll cut my losses and take them up.

Is it 3:1 mortar mix?

 

[K-Rod]

Thermo (and all),

Does the mortar go directly onto the 50mm of compacted sharp sand or do I have to remove all the sand and put the mortar onto the compacted hardcore?

Thanks.

 

[noseall]

Thermo (and all),

Does the mortar go directly onto the 50mm of compacted sharp sand or do I have to remove all the sand and put the mortar onto the compacted hardcore?

Thanks.

you could do as Thermo has already suggested

shovel up the sharp sand and re-use it for the mortar

...Or you can lay directly onto the sand OR directly onto the stone. Either way, provided you solid bed, it won't matter.

 

[K-Rod]

Can anyone estimate how much sharp sand and cement I would need for a 25m square mortar bed please?

 

[Thermo]

approximatley 2 bulk bags and 12 bags of dust

 

[K-Rod]

Cheers Thermo.