Laying brick on a compacted base?

[Tony K]

Afternoon. 

In preparation for the construction of an L shaped seating corner I have compacted hardcore and type 1 to a combined depth of 100mm min, as shown in the attached photo. The soil underneath is exposed clay (i.e the topsoil has been stripped away) but the area benefits from a French drain. 

 

I was thinking of laying brick straight on to the compacted base, but I'm concerned the brickwork will crack over time. 

 

What's my best option here? 

 

1. Lay brickwork on the compacted base. 

2. Cast a small (70mm deep) slab for the brickwork to go on. 

3. I've got some old 40mm solid concrete slabs. I could lay them on a thin bed of cement, then build the brickwork on top of the slabs. 

 

Any advice greatfully received! 

[saveasteading]

I would certainly lay a bed of sharp sand as a minimum, for control.

Long term, you will get some movement, weeds ants and worms. That can be dealt with.

 

A concrete layer would reduce these issues.

Bricks on slabs on hardcore seems wrong. I'm not thinking about why.

[Canski]

I think he means building a wall and not laying pavers.

[Tony K]

2 minutes ago, Canski said:

I think he means building a wall and not laying pavers.

I do, though its not quite a wall, more like this, with corners etc.. 

 

[Canski]

I thought so 🙂 Personally I wouldn't build a brick wall without a suitable concrete foundation.

[Mike]

Yes, concrete foundations for me too.

 

Edited July 9, 2023 by Mike

[Tony K]

50 minutes ago, Mike said:

Yes, concrete foundations for me too.

 

 

I'm sure you're right, but I just wonder if I have any options. 

 

My original idea was to build a patio with freestanding garden furniture (hence the subbase etc) but then I changed my preference to a brickwork seating area, and now I'm really keen on the idea! 

 

I've seen garden steps etc built on existing patio slabs, but never understood if it was really OK. I wonder if I'd get away with something similar here if I laid 40mm slabs and built on top? 

[Dave Jones]

just how our 1895 house was built. 4 bricks below ground zero concrete. Heaby clay area and never moved in 120 years, well until i put the 5 tonner though it.

[Iceverge]

17 minutes ago, Tony K said:

. I wonder if I'd get away with something similar here if I laid 40mm slabs and built on top? 

 

 

Your issue is differential settlement.

 

You can tackle this by either having a very consistent strength of substrate to your foundation or else having a strong foundation that will ensure the whole structure sinks/moves evenly and prevents cracking. 

 

You are going for the first solution.

 

Thinking out loud here. 

As a idea you could hammer some timber pegs to the point of refusal under the paving slabs and then trim them level with the hardcore. They would act as mini piles. 

 

Otherwise consider 2 layers of paving slabs with the joints crossed. 

 

Probably overkill. 99% sure if you build bricks straight onto the hardcore it would stay put. 

 

 

[Tony K]

8 minutes ago, Iceverge said:

 

 

Your issue is differential settlement.

 

You can tackle this by either having a very consistent strength of substrate to your foundation or else having a strong foundation that will ensure the whole structure sinks/moves evenly and prevents cracking. 

 

You are going for the first solution.

 

Thinking out loud here. 

As a idea you could hammer some timber pegs to the point of refusal under the paving slabs and then trim them level with the hardcore. They would act as mini piles. 

 

Otherwise consider 2 layers of paving slabs with the joints crossed. 

 

Probably overkill. 99% sure if you build bricks straight onto the hardcore it would stay put. 

 

 

 

Thanks very much for this. Regarding the timber piles idea, I could even go one better and use a load of rebar rods I've got lying about. 

 

Then I'll lay patio slabs, then repeat with joints crossed. 

 

Cheers! 

[Brickie]

9 hours ago, Dave Jones said:

just how our 1895 house was built. 4 bricks below ground zero concrete. Heaby clay area and never moved in 120 years, well until i put the 5 tonner though it.

Actually it will have moved-the creep of the building,as it’s known. 
It’s just that the lime mortar it’s almost definitely built in can accommodate this gradual process. 

[Conor]

My dad built his glasshouse base and small garden walls on a base of concrete blocks on their flat on top of a layer of quarry dust. Nothing moved or cracked.  

 

Bricks directly on the ground will definitely move and crack. You need a little more.