patio slabs gaps

[dotto]

Hi guys.
I am laying my patio and used sharp sand without cement as a bedding for the slabs.............i know it is not the proper way to do it but the old slabs had been there for 15 years resting on a bed of sharp sand only and experienced no much movement as the soil is clay and very firm so i did not want to change something that had been working fine for so long and that is the reason why i opted out for the cement. Anyway, the reason why i am posting is that i used sharp sand to fill in the gaps between the slabs but after a few days the sand has flown away already Do you think i should be using building sand to fill in the gaps instead of sharp? Any advice would be much appreciated. Thank you in advance

 

[imamartian]

i'm not an expert, but i'd mix sharp sand and cement and brush that in... it'll 'go off' with the damp in the air, and be there for a good long while!

 

[Thermo]

only way to do it is with a damp mix of mortar worked into the joints. having said that it will crack up over time due to the way the slabs are laid

 

[steveb1964]

Forget dry mixes for pointing. It will need to be a damp mix

 

[imamartian]

Forget dry mixes for pointing. It will need to be a damp mix

I think it depends on the size of the gap between the slabs... if the gap is above 5mm then i'd probably use a wet mix. But any less than 5mm, then a dry mix will be far easier to get in.
Plus, if done properly, the dry mix should drop to the bottom of the gap, and even fill in any dints left by the edges of the slabs when they were laid.

But that said, i'd never lay slabs just on sand.....

 

[Thermo]

sorry martin, but dry mix is ****e and never works. youre leaving too much to chance with the setting of it.

 

[imamartian]

who's martin?

but with respect Thermo, you may have a vast experience, and have your preferences, but you can't make sweeping statements like "it never works".

I'm not in the trade, but have laid lots of slabs, and read many sources that recommend a dry mix. My preference is to use it in a smaller gaps.

The mistake a lot of people make is using it to try and 'tie' the slabs together. Whereas it should only be used for neatness, to keep running water out and to inhibit weed growth.

 

[Thermo]

up to you, but why do you think no decent paver uses that method

sorry martian

 

[imamartian]

up to you, but why do you think no decent paver uses that method

sorry martian

doon't apologise, nothing wrong with healthy disagreement.

 

[Thermo]

i was apologising for getting your name wrong, not for the my view point.

the reason it is doomed to fail is if it is swept into the joint it is not packed in tight and therefore can sink, even if topped up when dry, as water will drag it down. There is no control over the moisture content and therefore the cement can dry off before it gets any moisture and then it is useless.
SO there may be one or two instances where it has worked, but in my experiance i have nevere seen a patio where it has worked.

 

[imamartian]

i accept it's not as good as a wet mix. But typically in this country, there's enough moisture around to help it go off properly, and a quick once over with a watering can would help.

My main point is though, if the gap is very small, you'll struggle to get a wet mix in the gap and especially to the bottom - taking it to extremes, you'd never see a wet mix used on block paving.

 

[Thermo]

no because block paving is a flexible paving and therefore any firm type of pointing will not work, which is why sand and only sand is used for the jointing, and that acts as locking mechanism on the blocks when it is vibrated in, which achieves a total fill of the gaps, after several applications. you cant do that with paving slabs.

Your statement about enough moisture in this country show a complete lack of understanding or experiance about it. Dont take it personally but it is bad advice and it is certainly not the best way to do it.

 

[imamartian]

yeah the block paving was an analogy to show my point about the small gap size...

and the advice i give is from many a written source, so has as much standing as any advice. And i did say that a watering can would help add enough moisture...

 

[Thermo]

oh well it must be right then you do it your way and any cowboy paver that wants to do it can do it that way as well

 

[dotto]

oh well it must be right then you do it your way and any cowboy paver that wants to do it can do it that way as well

Hi guys thank you for your pieces of advice. I have filled the gaps with dry mix and watered with watering can but unfortunately is crumbling and not working. Thermo when you say wet mix 1) how wet should that be..............2) what proportion of sharp sand and cement (3:1 is ok?) 3) how do i clean the slabs? 4) do i need several applications of that or just once is enough? Thank you very much for your time.