Topping up patio joints/grout...

[whoschuffed]

Had my patio down for about 8 weeks or so now and got round to giving it a wash down over the weekend as I was using some rust remover on bits. The water (and no doubt some of the rust remover overspill) appears to have taken away some bits of grouting.

Some of the current grout felt sandy and I could rub some of it away with my finger which I'm assuming means it didn't have a lot of cement in it.

Would I be OK to top these bits up if I make a dry mix of sand and cement and brush it back in to the gaps and wet it? It was originally jointed in this way.

 

[r896neo]

This will not last at all, and the original pointing will not last long either if it was done in this method. I wish the idiots who still spread this around as a suitable pointing method would give it up.

You have seen first hand how soft it is and really its generous to call it mortar.

You need to rake out the joint to at least 25mm depth and then point it using a damp mix which is firmed and pressed in with a jointer/ trowel.

 

[whoschuffed]

That's annoying! There isn't a lot which has come out so I may just do some spot top ups with a wet mix when i've raked them out. Some of the joints are wider than others too.

I imagine its going to be very difficult to get the colours to match aswell!

If the current sand/cement dry mix stuff is naff what would be the best thing to do? Completely rake out the whole patio and repoint?

 

[r896neo]

Yes if you want it to last then rake out and repoint properly. Matching colours will be a problem.

The one benefit to this method of pointing is that it is a least easy to rake back out.

Cement needs to be hydrated to start curing so you need to mix the whole batch up with water and then throw it out onto a wooden board which will suck some of the moisture out and leave it semi dry so that it can be forced in and ironed without being so wet it will stain the paving.

The old dry mix and water method leave so little of the cement hydrated that it doesnt really harden, added to the fact that there has been no compression to make it denser and stronger like ironing with a jointer or trowel would do.

like this

 

[whoschuffed]

I think i'll redo it with some of the VDW 800 Epoxy Mortar that comes recommended on Patio Expert in the next few months. One 25KG bucket should be enough for my top patio which is where it needs doing the most - its pricey though (£80 a bucket!).

Just need to rebed 2 slabs first though as I noticed a very very very slight wobble in two of them which should be fine with a stronger cement mix underneath.

 

[r896neo]

The 2 part resin mortars are real quality and pretty bullet-proof. If you cant face spedning it then marshalls weathpoint 365 is probably the best of the one parts although gtfk make a one part too which is very similar.

If its not a big area you could use normal mortar in a pointing gun which is slower but very cheap and will give a stronger joint than using semi-dry