scratch coat.

[kev richy]

Afternoon all.I have just looked at bathroom job on a new build and 3 of the 4 walls have a scratch coat on ,builder says it will be ok to tile on.I was wondering if this is correct. I will be using spf addy and bal apd primer.Hope this makes some sense .thanks in advance,kev.

[Sir Ramic]

Plaster or cement render?

[kev richy]

Not sure its grey and plaster said it was fine to tile on, he said just pva and tile ,but no way will i use pva! Thats wot made think i should ask on the forum. Sorry if this a daft question but i really want to make sure of job. Thanks for speedy reply.

[Phil Hobson]

If the wall can be scraped away with your thumbnail, it's probably plaster, if not sand/cement render. I would advise you to make sure which before thinking about the right primer and adhesive etc. to use. good luck.

[dock]

If you're using powder adhesive prime the plaster with a good acrylic primer then fix. If its cement:sand render then there is no need to prime before fixing

[kev richy]

Thanks for the advice,i use bal spf and bal apd primer. I live in west wales and no mapei supplier in area !

[Ajax123]

Would a scratch coat be flat enough to tile onto. My understanding is that the scratch coat is just a preliminary levelling coat to take out major uneven-ness out of the subsrtate and to make sure that the over all coat depth of render is not too deep. This is then topped off with a second top coat which gives the nice even surface.

[Dave]

If it is backing/bonding coat..then it is not a suitable substrate to tile too..

[whitebeam]

As scratch coat does it have deep horizontal lines or shallow circular lines

[doug boardley]

was thinking the same 'beam, ie is it a scratch or a float render coat

[TF Ed]

if its a new build it will more than likely be a backing plaster as you very very rarely get sand and cement now..

also, its worth mentioning that if the backing plaster has been left for a few days/weeks,, then the suction is going to be pretty strong!!

[Richardk]

Whats the difference between bonding, backing, browning, scratch etc? Are they basically the same sort of undercoat for plaster prior to a finishing coat?

[kev richy]

Thanks for the replies.I think the lines are horizontal. Think should go and have another look and find more out.Not starting to tile for a while,it still needs to dry longer. If this is not suitable to tile,is the solution to skim ,let it dry out then tile. thanks again

[Diamond Pool Finishers]

if the lines are horizontal then this is the first coat,and not true to tile on, it will need at least a second coat before you tile it mate!!, then there is the queschion of weather it is sand/cement if it is you will need to leave it at least three weeks before you tile it,

[Bolter]

Dont you just love how builders know everything.

[TF Ed]

Whats the difference between bonding, backing, browning, scratch etc? Are they basically the same sort of undercoat for plaster prior to a finishing coat?

hi richardk

thistle bonding - is a backing coat designed for low suction backgrounds ie concrete, concrete block, engineering brick and plasterboard.

hardwall - is designed for high suction backrounds ie thermalite block, facing bricks etc

browing - is designed for higher suction backgrounds and was used alot is th e 80's but its softer than hardwall so its not that resisitant to knocks BUT it has a higher thermal value so some architects still like it over hardwall...

the idea is, you would float out/render untill around 11am and then skim what you've rendered in the afternoon, this way it all goes off consistantly, avoiding suction issues, cracking etc.

a scratch coat or dubbing out coat is normally only needed when the walls are really bad and you cannot achieve you desired depth in one hit. you would apply, rule off where possible, fill in any voids and flatten. you would then key up using horizontally waves to give it a good key.
later that day for backing coats and usually the next day for sand and cement, you would then apply another coat, rule off, fill in and rules oof again and then FINALLY key up the render using circular or figure of 8 passes with you devil float. (a wooden or poly float with nails/screws in the end, normally 4) now it would be ready to skim..

recap horizontal lines normally mean that theres another coat of render to come..fig of 8 or circular normally mean its ready for skimming but if in doubt, put you straight edge on the wall and see how flat it looks anything over a couple of mil is rough imo (prior to skimming)



long winded explaination but fire away if theres any other questions mate.

[Diamond Pool Finishers]

back to my wats the term in your area thread,
rendering is---sand/cement
floating is---------- backing plaster in oxfordshire!!! not trying to be funny here aston old mate

[TF Ed]

yeah its the same in merseyside too but i know a lot of tilers on here refer to render for both backing coats and sand and cement so i was just trying to get the main point across thats all mate ....

regards
Ed

[Diamond Pool Finishers]

you did a good job to mate good read thanks

[whitebeam]

Were,nt quick enough Aston but well said

[Colour Republic]

I've noticed that a fair few plasterers become tilers as opposed to say chippys becoming tilers, Is it just because you feel comfortable with a trowel? What made you take up tiling?

[whitebeam]

They seem to work together and works as a related trade, Obviously I've done a lot of rendering and plastering for tilers.

Just seemed the next step up.

[Colour Republic]

Just seemed thenext step up.

Not sure if those are the right words Plastering is I believe a highly skilled job, if you're any good. Shame that so many 'plasterers' make a pigs ear of it. I won't employ a plasterer unless i've seen his work and when you find a good one you hang onto him for dear life!

Do you still advertise as a plasterer i.e. just take on plastering jobs? or do you just do it for your own prep now?

[whitebeam]

Still do the plastering in small amounts now but have worked for so many still get calls even from plumbers who do there own tiling.

At the end of the day work is work, until the old back lets me know when I'm pushing my luck a bit.

[TF Ed]

I've noticed that a fair few plasterers become tilers as opposed to say chippys becoming tilers, Is it just because you feel comfortable with a trowel? What made you take up tiling?

the reason many plasterers take to tiling as opposed to joiners is because the old city and guilds plastering course contained a module on tiling.

obviously using a trowel day in day out helps the transition but the biggest advantage a plasterer has in tiling is that they understand substrates, floor screeding, tanking and dry lining, so theres a really good platfrom to build from.

you do need to have a patience and a creative side to your ability which is not in every plasterer lol but i'd say your a quarter of the way there if your a plasterer....the knowledge of stone work, setting out & design and perfecting your cutting skills imo makes up the rest.

[whitebeam]

Well said that man

[Colour Republic]

the reason many plasterers take to tiling as opposed to joiners is because the old city and guilds plastering course contained a module on tiling.

Didn't know that thanks

[clive matthews]

hi guys , in answer to richardk horizontal lines are a scratch coat prior to finish level undercoat , browning is a light weight undercoat for clean masonry and bonding is a lightweight undercoat for multiple surfaces and the only lightweight that will stick on to any surface aslong as suction is controled , bonding is also the nickname fro dry wall compound for sticking plasterboard onto masonry dont let merchants give you the wroung stuff, also be carefull on moisture check plasterboard (the green stuff) the manufacturers dont band it about but it rejects certain materials put onto it beacuse of moisture resistant surface cheers clive