Old patio freshly repointed

[AidanGee93]

Hi all, looking for some advice here...

 

Got an old patio that was laid on soil and sand years back, took the weeds out and pressure washed and patio is solid no movement but repointed to stop any weeds coming through...some gaps are a bit more than others with some gaps smaller (patio laid on a slope so shifted over years but like I say solid no shifting now).

 

I made a pointing mix of 2 parts builders sand 1 part cement and added a tiny amount of Feb mix...zero water was added but the consistentcy of the mix I could squeeze into a ball without it crumbling so heard that's ideal.  Brushed the mix into gaps and compressed quite deep with a finger pointing tool, repeated and then finished with a smoothing pointer before moving to next slabs. After finished due to the following days being dry I lightly mist coated the area and done this 2x per day for the following days.  This was done start of September so temperatures were good.

 

Overall I'd say about 85% of the repoints are solid. The other 15% it's as if the mix has dried and lifted as slight bounce in it where it's not adhered to...not sure why that's happened but any tips?

 

I've been suggested go 3:1 for next mix add Feb mix only tiny amount aswell as a little SBR as ideal for outside work. Remove loose mortar, dust etc and repoint? Any other tips or your thoughts as to why the repoints lifted would be great. (Will post pics)

[AidanGee93]

[AidanGee93]

[Roundtuit]

Difficult to tell from the pics, but I'd guess it's not deep enough. Don't know what best practice is, but I'd be looking for maybe 15mm plus.

[Andehh]

Looks too shallow IMO. I'm not an expert though.

[AidanGee93]

I think what is must be is some of the slabs are bigger spacings than the others so possibly just the shallow gaps thats no took well. I'll try again with a little SBR in it tho point it compacted... hopefully works out....happy with the bulk of it 

[scottishjohn]

maybe you should have brushed all the gaps with water before pointing ,,as a very dry mix will be hard pressed to adhere to dirty msoil contaminated and dry gaps 

 

we do the same when pointing granite  in dry conditions ,even more wetting if it was sandstone as it is pourous abnd will suck all the water from the mix and not bonnd 

 but no water will be a mistake 

 then use a small damp l brush carefully  to finish it off before it sets 

 I doubt you can just put it in like putty and get a good bond

 try a small area and see if it works fro you before pulling it all out to redo

Edited October 17 by scottishjohn

[scottishjohn]

On 05/10/2024 at 16:05, AidanGee93 said:

 

On 05/10/2024 at 16:05, AidanGee93 said:

your picture shows an uppr line which was mortar bonding to the outer edge,which was brushed 

 and the horizontal line has been done the same

Edited October 17 by scottishjohn

[Cag]

First you've got to understand the cause, in order to know what to do: It could be insufficient cleaning: If the existing mortar was not adequately cleaned and prepared before applying the new pointing, the adhesion could be compromised. OR it could be incorrect mortar consistency: If it's too dry, it may not adhere properly. OR it could be temperature fluctuations: Rapid temperature changes, especially during the curing process, can affect the mortar's adhesion.

A few ideas I'd suggest:

• Consider using a 3:1 sand-to-cement ratio as suggested. This can provide better strength and adhesion.
• Add SBR: Styrene Butadiene Rubber can enhance the flexibility and durability of the mortar, especially in outdoor applications.
• Remove any loose mortar, dust, or debris from the joints. Use a wire brush or a chisel to clean them thoroughly.
• Before applying the new mortar, slightly dampen the surface of the existing slabs. This will help the mortar adhere better.
• Ensure that the joints are filled to the top with mortar. Avoid leaving voids or gaps.
• Use a pointing tool to compact the mortar firmly into the joints.
• Finish by smoothing the surface of the mortar to a consistent appearance.
• During the curing process, protect the repointed areas from excessive moisture loss. This can be done by covering them with a damp cloth or plastic sheeting.
• Avoid direct sunlight - it can cause the mortar to dry too quickly, affecting its strength.
• If the gaps between the slabs are particularly wide, a joint filler can be used as a base before applying the mortar.

 

Just for extra credibility - I'm a professional landscaper from https://battersealandscapers.co.uk/ - hope this helps