Posted: Mon Aug 02, 2010 9:38 am
Hello (again)
Having received excellent advice recently in another thread, I thought I would ask for your indulgence once again. Here's the problem first, the explanation + question (if it isn't obvious) follows:
Problem:
My bedding layer is crumbly (I can break it with my fingers) and has not adhered to the slab beneath, nor have the stones adhered to it particularly well.
I am in the process of removing it all to redo it. Thankfully it was only a small section of my overall project!
Explanation:
I am covering a patio with Solnhoffen crazy paving. I have been helped for most so far by a professional mason, who does everything by eye. Wanting to do a bit myself as he is unavailable for a few days, I reproduced his approach exactly, except for the bedding mix proportions, which I have been unable to determine as he does it without measuring anything. I therefore consulted this site and took the 8:1 proportions stipulated on the bedding mix page.
I already have a concrete slab upon which I am spreading my bedding layer.
I made the 8:1 mix, and I was careful to mix the sand and cement completely before adding the liquid. I used a plasticiser in the water (SikaLatex), and made the mix quite moist (not wet). It was immediately clear to me that my mortar was considerably sandier than that which my mason friend has been making...
I wet the slab and spread a bit of this mix into the water, and across the slab surface first, then I levelled my bedding appropriately. It was a hot day, and the work site is in direct sun.
I sprinkled the surface of the bed with cement (someone has already told me that this is not an ideal approach, but this is how my mason is working, and it has worked well for 90% of what we have done so far... The Solnhoffen stones are very flat, like tiles). Then I wet the individual stones before placing them and tapping them to level.
Working alone, inexperienced, this did not go super fast, and my bedding began to dry out. I remoistened it once with a fine spray of clean water.
And it's a disaster! As I said, it didn't adhere to the slab, and the individual stones, although not "loose", are very poorly held, and easy to unstick with the lightest lateral impact for the most part. Some of them come off clean, others have grabbed onto the cement layer, but this had pulled free from the bedding. I am removing what I did now, and the chunks of bedding that come out look sandy and I can crush them in my hand.
The rest of the project, done by my mason friend, is solid and well adhered.
Question
What did I do so wrong??
The mortar is clearly way too lean... Did I misunderstand the mortar instructions? (Standard Bedding Mortars)
Many thanks for your wisdom!
Having received excellent advice recently in another thread, I thought I would ask for your indulgence once again. Here's the problem first, the explanation + question (if it isn't obvious) follows:
Problem:
My bedding layer is crumbly (I can break it with my fingers) and has not adhered to the slab beneath, nor have the stones adhered to it particularly well.
I am in the process of removing it all to redo it. Thankfully it was only a small section of my overall project!
Explanation:
I am covering a patio with Solnhoffen crazy paving. I have been helped for most so far by a professional mason, who does everything by eye. Wanting to do a bit myself as he is unavailable for a few days, I reproduced his approach exactly, except for the bedding mix proportions, which I have been unable to determine as he does it without measuring anything. I therefore consulted this site and took the 8:1 proportions stipulated on the bedding mix page.
I already have a concrete slab upon which I am spreading my bedding layer.
I made the 8:1 mix, and I was careful to mix the sand and cement completely before adding the liquid. I used a plasticiser in the water (SikaLatex), and made the mix quite moist (not wet). It was immediately clear to me that my mortar was considerably sandier than that which my mason friend has been making...
I wet the slab and spread a bit of this mix into the water, and across the slab surface first, then I levelled my bedding appropriately. It was a hot day, and the work site is in direct sun.
I sprinkled the surface of the bed with cement (someone has already told me that this is not an ideal approach, but this is how my mason is working, and it has worked well for 90% of what we have done so far... The Solnhoffen stones are very flat, like tiles). Then I wet the individual stones before placing them and tapping them to level.
Working alone, inexperienced, this did not go super fast, and my bedding began to dry out. I remoistened it once with a fine spray of clean water.
And it's a disaster! As I said, it didn't adhere to the slab, and the individual stones, although not "loose", are very poorly held, and easy to unstick with the lightest lateral impact for the most part. Some of them come off clean, others have grabbed onto the cement layer, but this had pulled free from the bedding. I am removing what I did now, and the chunks of bedding that come out look sandy and I can crush them in my hand.
The rest of the project, done by my mason friend, is solid and well adhered.
Question
What did I do so wrong??
The mortar is clearly way too lean... Did I misunderstand the mortar instructions? (Standard Bedding Mortars)Many thanks for your wisdom!
