Bubbles under paving anything to worry about??

Discussion in 'Builders' Talk' started by Liamb2018, May 16, 2022.

  1. Liamb2018

    Liamb2018 New Member

    A little back story in the hopes it helps saves someone some of the huge stress we have had to endure.

    Over a year ago I hired a builder to lay some Indian stones in our garden 120m2 in total so quite a large area.

    After a few months of delays and the stones were laid we started to notice really hard square stains appearing, later found to be reflective staining from not using a full mortar bed (which we had luckily requested prior) after a dispute he dug the entire lot up and laid them again, unknown to himself (he claimed) and us, the stains came back despite the second load being a full mortar bed.

    As I’m sure you can imagine with 120m2 area that also came with a huge pile of rubble at the front of our property, made even bigger when me and my son had to dig the second ones up again. That builder went awol and I found out I was in a long line of people taking legal action against him over the last 5 years. A situation we have since given up on.

    A few moths after this a friend of my brothers offered to help lay the paving properly so we ordered the stones again (which was very costly :( and he finished around 4 months ago. Since then we’ve pointed it with easy joint as well as doing a lot of other work all stones seem solid.

    This weekend my wife noticed every time it rained and she stepped on 5 or 6 stones (so far) that they bubbled andwould foam from under the stones.

    In doing some research I read on paving expert that stones should be laid with sbr (not pvc) so I asked my brothers friend what he used to which he answered “PVC which I’ve been using for 15 years without any problems”

    Although none are loose as of yet I don’t think I can handle the thought of pulling them all and rendering / paying someone render 120m2 a 4th time so I was wondering…


    A) does bubbles after raining mean they are unsticking :( ?? Or is it to be expected

    B) knowing my past luck I’ll bet they come loose eventually so am aware the best thing would be to dig up the old render and start again but I don’t have the funds or the frame of mind for that so I’m wondering if anyone has had any luck with lifting them and sbr on the back with adhesive like ct1 as I’ve read on various pages and I’d so how it went, did they stick, could it stain my stones or…am I completely screwed??
     
    NewApprentice23 likes this.
  2. Mr right first time

    Mr right first time Active Member

    Maybe you should give up and get some Astro turf
     
    gadget man likes this.
  3. Hausfix

    Hausfix Screwfix Select

    There is so much here that doesn’t make any sense to me..
    What do you mean by “bubbled” and “foam under stones”?
    “Render” is a sand and cement decorative coating you apply to walls, what are you referring to when you use this term?
    “PVC”.. do you mean PVA?
    The “Indian Stones” you refer to, are these flat slabs, possibly grey slate paving slabs, that have been laid to create a patio?
    “Pointed with easy joint” what do you mean by that?

    Sorry to ask all these questions, but it will help to come up with a relevant answer..
    Is it possible to post some photos of what you are asking about and also some photos of the ‘staining’ you’ve mentioned?

    On the assumption that you are describing a patio area, made up of square/rectangle natural slate paving stones, I can’t see why you would expect to see stains coming through as a result of setting them on a ‘5 spot’ bed of mortar as opposed to a full mortar bed. The staining is more likely to be an issue with contamination acquired during manufacturing, processing, storage or transportation of the material. A coat of SBR on the underside of the slate slabs prior to laying is the correct method to ensure the best adhesion, PVA isn’t suitable and will have no effect long term.
     
    Last edited: May 17, 2022
    NewApprentice23 likes this.
  4. Liamb2018

    Liamb2018 New Member

    Thanks for your reply and sorry for the confusion I was tired and quite stressed when writing it.

    By bubbling I mean when it’s been raining and wet when we stand on the stones bubbles / foam come out from certain areas around the edges of the stones basically air escaping which makes us think a gap is appearing and they may be coming lose.

    by render I mean the sand cement mix the builders put down on top of the hard core, around 4 inches of then compacted the stone onto with a mallet.

    yes pva not pvc sorry

    India stones as in grey calibrated kandla 25mm flat 600x900 flags to be exact on a few areas of our garden as a patio.

    the staining is known as reflective staining (I’ll attach pics). You don’t lay dot and dab or 5 blobs on Indian flags due to how thin they are (or around the edge and a line through the middle like our first builder did) otherwise the moisture separates the minerals as we found out the hard way, it’s all explained on paving expert. Since changing to a full mortar bed and nee stains we’ve never had the same problem.

    we are aware now you are supposed to sbr (and not pva) the stone while using a full mortar bed but unfortunately it’s too late for that now (as mentions that would mean a lot of rubble @ 120m2 and the 4th time paving the garden due to issues with builders not paying them properly.

    At the moment no stones are actually loose they are all solid but a few of them are bubbling when wet so assume this means there is tiny cavity’s / space between the full mortar bed and stone which I can only imagine will get worse.

    I want to know if I use sbr on the back of the slab can I stick down these bubbling stones again without having to rip up the full mortar bed ? Will they stick ?

    Images to follow
     
  5. Liamb2018

    Liamb2018 New Member

    Hi hausfix,

    here is an image of the stains that appeared known as reflective staining, and a pic of what caused it. Ie because he didn’t use a full mortar bed. Dot and dab etc or leaving any cavity is a big no on Indian stones - it explains here better than I can on paving expert https://www.pavingexpert.com/stain_reflective_01

    Since laying with a full mortar bed and new stones the stones both look fine and have been solid for months (despite him using pva over sbr), no rocking, hollow sounding when tapping then or movement etc , other than the bubbling mentioned above.

    so keen to know if we can pull them up and sbr them back down to prevent them getting worse?

    Any help or advice would be appreciated.
     

    Attached Files:

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice