The Brew Cabin

Posted: **Thu Aug 06, 2015 7:38 am**

A company came and laid a patio and the mortar between the slabs is quite crumbly in places - it comes away easily if I dig my fingernail in. The mortar is very shallow in places too, almost to the size of a 20p piece. I assume none of this is good?

The company has agreed to come back to correct it but I was wondering if they need to dig out all the crumbly mortar first or if it is acceptable to fill up the shallow parts with new mortar on top of the old crumbly mortar?

They told me the pointing would be 1.5-2cm wide but it is 3cm in places. Other than aesthetics, is this an issue?

Thanks in advance for any advice.

Posted: **Thu Aug 06, 2015 9:02 am**

Hello

There are a couple of reasons why the mortar is crumbling. Either it wasn't mixed properly, there is not enough cement in it or it was to dry and hasn't set correctly.

Patching up the loose areas will sadly not suffice. They need to rake out all the mortar and do it again properly using the same mix.

Re the joint width, it really depends on what the paving material is. If its Indian sandstone then the joint width should be 10-15mm max. If it is Indian Sandstone with joints up to 3cm wide then that indicates that the stone has possibly been laid upside down.

Can you post a picture?

Steve

Posted: **Thu Aug 06, 2015 9:51 am**

Thanks for your reply. I'm having a problem posting a picture as when I click on the Image button it asks for a URL and my pictures are not on a website. Is there another way to post a pic?

Posted: **Thu Aug 06, 2015 1:56 pm**

email one to me and I will post it for you

steven@londonstone.co.uk

Posted: **Thu Aug 06, 2015 6:00 pm**

I emailed some pics to you earlier this afternoon.
Thanks

Posted: **Thu Aug 06, 2015 8:13 pm**

Nothing has arrived yet

Posted: **Fri Aug 07, 2015 1:40 am**

Just sent again. Please check your spam folder just in case. Thanks

Posted: **Fri Aug 07, 2015 8:28 am**

Photos uploaded on behalf of Apollo

A few things to consider here.

-The joint widths are a bit on the large side but not excessively. Certainly not large enough to warrant getting relayed.

-The stone has been laid the right way up, so nothing to worry about there. Looks like a reasonable job to be fair.

-Problem lies in the pointing. It looks grey in colour so I think there is enough cement in there. Looking at the finish on the pointing it hasn't been struck or tooled in. I think that they have brushed it in dry and then just watered it in. This method involves barely any compression of the mortar which results in a weak, crumbly mix. If this is the method they have used then its only a matter of time before all the pointing fails.

-You need to get them back to replace the lot. It may just be a lack of education on their part and if so why not point them in the direction of this site. Or if you don't have much confidence in their ability to put it right you could always use one of the brush in mortars. They are numpty proof

Cheers

Steve

Posted: **Fri Aug 07, 2015 5:37 pm**

I concur with what steve has said
the cement residue on the flags indicates to me that they have brushed in dry sand/cement and watered it in

the whole of the jointing need to come out and be re-done either with a suitable compound gftk vdw 800 or repointed with proper mortar

it looks like the pointing would come out with a jet washer

LLL

Posted: **Fri Aug 07, 2015 7:01 pm**

Jointing definitely needs redoing for all of the reasons stated above.
In regards to the width of the joints the could be wide to accommodate the size variation in the flags.
The lines are all straight and the levels look good as far as I can tell from the photos.
Just a shame the jointing has let the job down.
The surface staining will go with foot traffic, weather and time.

Posted: **Fri Aug 07, 2015 8:14 pm**

Where abouts in London are you Apollo?

Posted: **Sat Aug 08, 2015 1:03 am**

Thanks Steve for posting the pics and to all of you for your comments.
I am in East London (E1).

Posted: **Tue Aug 11, 2015 9:15 am**

They are coming back to re-do the pointing.

Another question I have is about the paving overhanging. They built a step and a flower bed and the slabs hang over about 2 inches. I was worried if someone stood on the end where it overhangs that the weight will be exerting a force down that would be pushing the other end of the slab up and that over time it could loosen the slab (especially if the pointing fails). Should I ask them to cut the overhanging slabs flush or do you think it's not necessary?

Posted: **Wed Aug 12, 2015 11:11 am**

They are back re-doing it as I type. He told me the mortar HAD been mixed, not brushed in, but the problem was that they had run out of builders sand.

He said he was intending taking off the top layer and lay new, properly mixed mortar on top to give a smooth finish. I told him I was advised it all needs to be taken out and done again.

Fingers crossed it will be done right this time.

Posted: **Tue Aug 18, 2015 11:29 am**

I can't see what difference the choice of sand makes - many contractors will use a coarse/sharp/grit sand (normally used for bedding) as a jointing mortar. OK, it looks coarser (obv!) but it should not be crumbly.

As for the oversail on the steps, see this page.....

The Brew Cabin

Crumbly mortar