Mortar Ratio & Sand Type for Single Course of Bricks

[Antony11]

Hello,

I recently laid a concrete slab for a shed to sit on top of, however over the longest length (5.5m) there is a 25mm difference in height. I know this is not ideal but I laid this in a day by myself which was quite the challenge.

So to correct the height variation so the walls can sit square I am planning on laying a single course of solid engineered bricks around the perimeter, and making the height difference up in the bed of mortar beneath the bricks.

So taking into consideration the first brick mortar depth at the highest point is going to be roughly 10mm, the lowest point will then be roughly 35mm instead of 25mm.

I have seen so much conflicting information about the type of sand to use and mortar ratios and am looking for some clear advice.

I am not so much bothered about mortar appearance being rough looking or not as its only a single course of bricks, the main thing I am looking for is Mortar Strength up to 35mm depth and brick/ concrete adhesion.

So my questions are:

1. What should the sand cement ratio be, 4:1?

2. Should I use Sharp Sand, Coarse Sharp Sand or Builders Sand or a mixture?

3. Can I use a plasticiser (I bought some today)?

4. Is it okay to lay this mortar on 6 day old concrete as its only a single course of bricks?

5. Do I need to soak engineered bricks?

Thanks,

Antony

 

[Celeronmanuk]

Maybe it would be easier to lay some timber bearers and pack them to level? Or adjustable pedestals like building a deck?

 

[Antony11]

Maybe it would be easier to lay some timber bearers and pack them to level? Or adjustable pedestals like building a deck?

Thanks for your reply, I thought about doing that but I will be left with a 25mm gap that will need filling. However that would be the much easier option.

I have already bought the bricks so am hoping to go with that option and they will at least keep the whole frame off the ground, just need some mortar advice..

Thanks

 

[Mr Chibs]

I've recently made some raised brick beds from old bricks, similar to you, I need to bring the level up at one end 30mm
I sat the first course on a 3:1 of sharp sand/cement mix. and 4:1 for the remaining courses.

Two days later, it's like rock.

Don't make the mix really sloppy... the less water used, the less it will shrink, and I'd wet the engineers.

I found it goes off quicker with sharp sand and not quite as easy to point (occasional small bits of grit)

hth

 

[Antony11]

I've recently made some raised brick beds from old bricks, similar to you, I need to bring the level up at one end 30mm
I sat the first course on a 3:1 of sharp sand/cement mix. and 4:1 for the remaining courses.

Two days later, it's like rock.

Don't make the mix really sloppy... the less water used, the less it will shrink, and I'd wet the engineers.

I found it goes off quicker with sharp sand and not quite as easy to point (occasional small bits of grit)

hth

Thanks for your reply,

Did you find that using quite a dry mix at 3:1 bonded well to the bricks?

Also did you use a plasticiser?

Thanks

 

[Mr Chibs]

Yes, if the mix is good, not too dry and not sloppy.

I didn't bother with plasticiser, but this may help, on one mix I used a bag of cement that went out of date, had to mix small batches as it started to go off quickly, but it's set well.

 

[Celeronmanuk]

You could add some SBR to the mix!

 

[tony1851]

I've recently made some raised brick beds from old bricks, similar to you, I need to bring the level up at one end 30mm
I sat the first course on a 3:1 of sharp sand/cement mix. and 4:1 for the remaining courses.

Two days later, it's like rock.

Don't make the mix really sloppy... the less water used, the less it will shrink, and I'd wet the engineers.

I found it goes off quicker with sharp sand and not quite as easy to point (occasional small bits of grit)

hth

Would you really wet the engineering bricks? They absorb little water and there is a risk of them sliding about if there is too much water around. In fact, although they used to wet bricks before laying in the old days, it's not normal practice now.
@op instead of having a 35mm thick bed joint at its thickest, can you not bed some thin hard material in it,such as pieces of slate or clay tile? A joint that thick in mortar might compress too much.
Building sand is better for mortar than sharp sand, which is too coarse and makes the mortar difficult to work with.

 

[Antony11]

Would you really wet the engineering bricks? They absorb little water and there is a risk of them sliding about if there is too much water around. In fact, although they used to wet bricks before laying in the old days, it's not normal practice now.
@op instead of having a 35mm thick bed joint at its thickest, can you not bed some thin hard material in it,such as pieces of slate or clay tile? A joint that thick in mortar might compress too much.
Building sand is better for mortar than sharp sand, which is too coarse and makes the mortar difficult to work with.

Thanks for your reply,

I have just put all the bricks in buckets of water! Maybe I'll let them sit a bit before using them so any excess water can drain off.

Would you still use building sand just for a single course of bricks? I don't mind taking my time with it and making small batches of mortar if I use sharp sand. In terms of compression its a timber frame with cladding going on top, not like a tonne of bricks. Even with just a timber frame do you still think a 35mm joint is too thick? I could add some tile in between but its another extra thing to buy and process to undertake.

 

[Celeronmanuk]

If I was doing this, I'd use normal bricklaying mortar (something like soft sand 5:1) and stick some pieces of roof tile in the thick beds as @tony1851 suggested.

 

[Antony11]

If I was doing this, I'd use normal bricklaying mortar (something like soft sand 5:1) and stick some pieces of roof tile in the thick beds as @tony1851 suggested.

Thanks,

So you don't think sharp sand is advisable?

I am assuming a standard building sand joint is about 10mm to?

 

[Celeronmanuk]

Thanks,

So you don't think sharp sand is advisable?

I am assuming a standard building sand joint is about 10mm to?

I've just not tried to lay bricks with it, but I know it's not as nice to use.