limestone coping and render loose

12 Feb 2014
Reaction score
United Kingdom
We had a retaing wall built in the garden in 2015 out of 7N dense blocks on their side. I placed polythene behind the wall going down to the footings. This was followed by terram which I formed into a channel that was filled with about a foot deep and wide of pea gravel with a 4" land drain wrapped in a textile sock at the bottom of the pea gravel so plenty of drainage

The wall was then rendered leaving an inch gap at the bottom and painted with masonry paint.

Each year the sides of the wall on the steps gets damp and subsequently the render comes away at the top. I repair this every year and repaint and it's becoming a bit of a chore.

Could it be that the wall is pulling damp up or is it that surface water is coming over the coping stones and getting behind the render somehow?

It only seems to be the side walls and the lowest step on the patio that are affected.

This also means that the coping stones are coming loose. I rebedded some of the top steps last year, I cut grooves in the stone and the concrete block of the step. Applied an SBR slurry to the bottom of the limestone and rebedded them on a full bed of mortar with frostproofer additive after wetting the concrete of the step. The mortar was solidly stuck to the steps but not the limestone.

The last photo shows the damp blocks on the side that I haven't rebedded the copings on before. The wires are coming out.

What am I doing wrong? What's the best practice for rebedding the limestone for a permanent fix on potentially damp concrete block?


  • IMG_20190609_133410.jpg
    464.3 KB · Views: 111
  • IMG_20190609_133431.jpg
    388.6 KB · Views: 118
  • IMG_20190609_133443.jpg
    454.7 KB · Views: 119
Sponsored Links

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links