rendering

[pandjrutland]

hi , I am rendering a lime stone wall ( inside )that has been pva sealed about 5 years ago . What is the best way to render it (so ready for skim )what should i use ( what mix ) . I have tryed sharp sand and cement and it just fell off ! I NEED HELP cheers paul

 

[plstering]

id be thinking of using an SBR slurry coat first
have you tryed weting the wall first
befor you start rendering
is it inside work or outside work
what mix you useing use (plastering sand) & cement say 4/1 with a dash of waterproofer in the mix
how many m2 is it ???????????
how you mixing it ie mixer/hand
hope we can help

 

[pandjrutland]

id be thinking of using an SBR slurry coat first
have you tryed weting the wall first
befor you start rendering
is it inside work or outside work
what mix you useing use (plastering sand) & cement say 4/1 with a dash of waterproofer in the mix
how many m2 is it ???????????
how you mixing it ie mixer/hand
hope we can help

HI , Whats a sbr slurry ?
no did'nt wet the wall
the works inside
i used sharp sand and cement 6:1 by a mixer

 

[plstering]

hi m8 sbr is a bonding coat used on dodgy backgrounds
Improves adhesion, bonding and flexibility.
• Designed for use in damp and wet conditions.
• Improves workability, strength and abrasion resistance.
• Reduces shrinkage and cracking in render mixes.
• Allows reduction in water content.
• Improves chemical and water resistance

All surfaces should be structurally sound, free from laitence, oil, grease, paint
and surface water. This can be achieved by grit blasting, mechanical scabbling
etc. to provide a clean and fresh exposed surface.
Before the application of a bonding slurry coat, surfaces of high suction
should be thoroughly dampened down.
An SBR bonding coat slurry should always be used on surfaces with
low suction, when applying sand-cement render mixes and also before the
application of a waterproofing system – see specification overleaf

2. Renders
To produce a dense, impermeable render use 50kg OPC, 125kg clean,
sharp sand (BS:1199),with 15 litres of SBR additive and mix with water as
required. Apply render in two well scratched 6mm coats to give 12mm
thickness overall. This will give 8 square metres of rendered wall. Allow 4-6
hours between each coat.
3. Damp Proofing
Where dampness is present or expected, either below or above ground, then
three coats of bonding slurry should be applied before application of any
further render or waterproofing system. Each slurry coat should be allowed to
become ‘touch dry’ before the next coat is applied.
4. Flooring
To produce high quality, hard wearing floor finishes use 50kg OPC, 75kg
sharp flooring grit, 75kg granite chips (3mm) with 10 litres of SBR additive
and mix with water as required. This will give 8 square metres of screed laid
at a 12mm thickness.
Prepare floor base well and apply bonding slurry. Mix materials semi-dry and
lay onto the slurry up to a thickness of 25mm. For additional thickness reduce
SBR to 5 litres and add extra water to produce a semi-dry mix.

 

[plstering]

i tend too mixe it with cement and water and brush it on or roller id use a plasterers wisk to knock it up just too get the lumps out and so its mixed propper
iv used it on a big rendering job over old brick and it turd out the mutz nutz
id try and wet the walls first befor shelling out on sbr or weber rend-aid
wet it down really well use a big sort brush too help work it in too the wall
on dodgy wall like that i tend too keep a weed spraying pump handy full of water
just too wet as i go if it starts too dry out

5/1 mix of plastering sand and cement with a dash of water proffer in the mix i tend too get two batches in the mixer then just add half a cup of water proofer to it sorted let it mix up a little bit after
are you using muilti finish plaster over the top ????????

id be float and seting the same day if the wll is sucking it in quick time

 

[spc]

I would approach it from another angle, pva has been on for 5 years, spray the wall down with weak pva and let it reconstitute the existing.

put a tight scratch of 4:1 sand and sulphate resisting cement with inegral waterproofer ( i used to live near oakham, thier walls are solid and full of salts) scratch a good mechanical key and leave for a couple of days to ensure adheasion.

then when you are happy its sound top with 5 sand 1 cement and one HYDRATED lime

then skim when set

nb: is there a dpm or chemical damp course? if not, steer clear from anything cementitious or gypsum based

 

[plstering]

id use Thistle Dri-Coat
A cement-based undercoat plaster for replastering after installation of a damp-proof course

it will save you `soo much time and fanning about just pva the walls 4/1mix
let it goo taky then hit it with this stuff m8 lay it on ruile it off fill dips ect
let it go devil float it and skim sorted
save money time and messing with mixs and cement mixers tell you what you get the gear and ill come and do it for you so you know for next time

 

[stevethespreader]

I have tryed sharp sand and it just fell off ! I NEED HELP cheers paul

you dont need sharp sand on internal work, as rendering indoors do not require the strengh outside render would require, u will find plastering sand or soft sand more suitable for inside work, also you did not mention using a plasticizer, if you wasent using any then it would have been hard to use

 

[plstering]

yer sorry my bad lads you can get a retarder with the lot in (all in one)

plastering sand or building sand is ok for inside work m8 i use plastering sand out side ill never use sharp agen the sharp sand in essex is like ballest
what ever sand you use m8 mix it 5/1 with your addy in the mix prep the walls get it on and flat and ready for skiming (but DONT over work it )
or put it on too thick or it will slupp
even if it takes 2/3 coats to get it were you want it then so be it

 

[spc]

Where in rutland are you? if my back eases up, ill have a ride out and come and see you. give you the best method that wont blow or efflouress

just a quick thought, thistle one coat? scratch it and top it. still contains gypsum though

 

[pandjrutland]

I have tryed sharp sand and it just fell off ! I NEED HELP cheers paul

you dont need sharp sand on internal work, as rendering indoors do not require the strengh outside render would require, u will find plastering sand or soft sand more suitable for inside work, also you did not mention using a plasticizer, if you wasent using any then it would have been hard to use

hi , sorry m8 what do you meen by a "plasticizer " do you mean pva

 

[pandjrutland]

i tend too mixe it with cement and water and brush it on or roller id use a plasterers wisk to knock it up just too get the lumps out and so its mixed propper
iv used it on a big rendering job over old brick and it turd out the mutz nutz
id try and wet the walls first befor shelling out on sbr or weber rend-aid
wet it down really well use a big sort brush too help work it in too the wall
on dodgy wall like that i tend too keep a weed spraying pump handy full of water
just too wet as i go if it starts too dry out

5/1 mix of plastering sand and cement with a dash of water proffer in the mix i tend too get two batches in the mixer then just add half a cup of water proofer to it sorted let it mix up a little bit after
are you using muilti finish plaster over the top ????????

id be float and seting the same day if the wll is sucking it in quick time

hi cheers m8 for the info , i thought i should render and then the next day skim
any thought on plaster bounding ?

 

[spc]

is it a solid9 inch stone wall?
rubble wall or faced stone?
lime bedded or cement?
damp proof course, injected or neither?
is the wall Flat or bent?

help me to help you???

If its flat and solid 9 inch ? dot and dab with thermaback plus and tape it if you are a novice

 

[stevethespreader]

I have tryed sharp sand and it just fell off ! I NEED HELP cheers paul

you dont need sharp sand on internal work, as rendering indoors do not require the strengh outside render would require, u will find plastering sand or soft sand more suitable for inside work, also you did not mention using a plasticizer, if you wasent using any then it would have been hard to use

hi , sorry m8 what do you meen by a "plasticizer " do you mean pva

no i dont mean pva, plasticizer will make your sand and cement mix more pliable and workable and help bind it together, completley different to pva http://www.diy.com/diy/jsp/bq/nav.jsp?isSearch=true&fh_search=plasticizer
also because the wall is pva'de that could be part of your problem because it has no suction, a little bit of suction will help pull it in and hold it on the wall

 

[plstering]

easy way too sort it is just too use a wire brush over it first