How to build a base for Travertine stairs?

[toffeeapple]

Hi all,

I am putting stairs in instead of the stepping stones for our front yard and hoping to extend it to the door which means to change the current tiles to the same Travertine.

Would someone be able to assist in guiding me on the base work prior to and if it's best to lay timber sleepers as a base instead of concrete?

This is the inspiration 

   

[toffeeapple]

Hi All,

I have done a fair bit of excavation and with the recent heavy rainfall, it has created a saturated clay soil (very gooey like). This is 150mm below ground level.

Does this mean I need to dig deeper and reach a more solid base? Or can I just add 10mm bluemetal or natural roadbase and keep compacting it?

[EricL]

Hello @toffeeapple 

Since you plan to use retaining wall blocks instead of a heavy concrete base over the saturated clay, the preparation remains crucial to ensure stability and prevent shifting or settling over time. The saturated clay can cause issues if not properly prepared, as it doesn’t compact well when wet.
 

To start, consider digging deeper if possible, to reach firmer ground. If that's not practical, focus on drainage and compaction. Begin by adding a thick layer of road base (100mm to 150mm), as it provides better stability than a thinner layer of blue metal. Compact this layer thoroughly with a plate compactor to create a solid foundation. If you’re concerned about moisture, incorporate a layer of coarse aggregate or gravel before the road base to aid in drainage and help prevent moisture buildup.
 

You may also want to lay a geotextile fabric between the clay and the base material to keep the road base from mixing with the clay and to ensure long-term stability. This fabric helps maintain drainage and prevents the foundation from shifting.
 

Once the base is prepared, you can start laying the retaining wall blocks. These blocks are designed to provide structural support but ensuring that the base is well-compacted and stable will help prevent any future movement. If drainage issues persist, installing a French drain or sub-surface drainage around the perimeter of the wall can direct water away and keep the base dry.

By properly preparing the foundation, you’ll ensure the retaining wall blocks remain stable and prevent settling or shifting as the weight of the wall and surrounding materials settles over time.

If you need further assistance, please let us know.

Eric