Is a New Skim Coat needed?

[sunshine99]

Hi,

I stripped all my front room Wallpaper away at the weekend with a view to tidying the walls so I can paint directly onto them.

Unfortunately a fair bit of the Skim Coat came away, some of the patches being around 50cm wide.

The walls are made up of Cement & Sand render with around a 3mm skim coat

Also as shown in the pic below, there is a worrying verticle crack around 4mm wide running the full length of one of the walls, this in the same area a Chimney breast was filled, I think it has settled after the work had taken place.

I was looking to patch this all up with finishing plaster such as this

http://www.wickes.co.uk/Finishing-Plaster/invt/224542

Then lightly sand after

From reading these forums I take it I would be wasting my time and effort as it would always be noticable after I painted??

If so would my best bet to get a Plasterer in to skim the entire room even though large parts of the existing Skim looks OK?

Also there is a lot of WallPaper Paste and Polyfilla (which is above the level of the Skim) still on the walls,

Would I have to wash the paste off and chisel the filler off (its rock hard) in preparation for new Skim Coat?

Thanks for your help,
Chris

Untitled

• sunshine99
• 22 Sep 2009
• 1

 

[Richard C]

Hi,
I stripped all my front room Wallpaper away at the weekend with a view to tidying the walls so I can paint directly onto them.
Unfortunately a fair bit of the Skim Coat came away, some of the patches being around 50cm wide.

Did you use a steamer to strip the paper?

Hi,
The walls are made up of Cement & Sand render with around a 3mm skim coat

Normal; how old is the property?

Hi,
Also as shown in the pic below, there is a worrying verticle crack around 4mm wide running the full length of one of the walls, this in the same area a Chimney breast was filled, I think it has settled after the work had taken place.

Probably not a problem & is almost certainly salvageable; but its work that requires stripping back to the blocks & a reinforced repair if it’s not to crack open again in 6 weeks

Hi,
I was looking to patch this all up with finishing plaster such as this
http://www.wickes.co.uk/Finishing-Plaster/invt/224542
Then lightly sand after

Forget it; it won’t work & will crack open again in a very short period of time.

Hi,
From reading these forums I take it I would be wasting my time and effort as it would always be noticable after I painted??

DIY effort usually end un disaster but not always!

Hi,
If so would my best bet to get a Plasterer in to skim the entire room even though large parts of the existing Skim looks OK?

I would advise it; after repairs of the nature you require, it’s (my) standard practice to skim the entire wall. In reality it doesn’t add much to the price of the repairs against filling & blending &, unless it’s done really well, you will always see it!

Hi,
Also there is a lot of WallPaper Paste and Polyfilla (which is above the level of the Skim) still on the walls,
Would I have to wash the paste off and chisel the filler off (its rock hard) in preparation for new Skim Coat?

All the paste will have to come off but the filler is probably OK as long as it’s sound & flush. I would advise asking your chosen plasterer to advise what he will accept by way of DIY prep. If I do a job, I prefer to do everything myself & give you the guarantee you would expect; you do the prep to save some cash & I won’t guarantee it!

 

[sunshine99]

Hi,

Thanks for answering my questions

Yes it was a Steamer, didn't have much choice as the wallpaper wasn't shifting, although some of the skim came off just by pulling the paper off the wall

The Property is Victorian (around 1890s)

Regarding the crack in the wall, out of interest, how does a builder go about reinforcing? This crack must have been there years would it not have settled by now? it will still appear even after it is filled?

Forgetting the crack in the wall would I be able to repair any of the broken skim using the finishing plaster that I mentioned?

I presume a plasterer would not be too keen on removing wallpaper paste and I would rather do this time consuming job rather than pay someone, but a lot of the filler on the walls is proud hence I have been using a chisel to remove to get it flush, do you think its best to stop doing this then?

Thanks again
Chris

 

[bathstyle]

I would knock off the skim coat either side of the crack and apply some scrim tape to the crack, you Will need to apply the scrim with neat PVA, just brush some on the crack, stick scrim on then brush on some more PVA.

The missing plaster and the crack can now be filled with plaster. In an ideal world the wall should be covered with a watered down PVA and Multifinish plaster.

As this is a DIY website I suggest using a one coat plaster or some sort of patching plaster.

Even if you don't get the wall absolutely perfect you can fill any voids in your plaster afterwords with Gyproc Easi-fill (B&Q sell it). This stuff will come in handy as I can see other parts of the wall need to be made good too plus ideal for other rooms that need doing.

 

[Richard C]

Hi,
Yes it was a Steamer, didn't have much choice as the wallpaper wasn't shifting, although some of the skim came off just by pulling the paper off the wall

Problem with using steamers is they will “blow” the skim coat off a render base if you apply too much concentrated heat; this may have contributed to your problems.

Hi,
Regarding the crack in the wall, out of interest, how does a builder go about reinforcing? This crack must have been there years would it not have settled by now? it will still appear even after it is filled?

Is that an internal or external wall? Given the age of the property, I assume the external walls are solid construction & not cavity? If it’s an external wall, are there any corresponding cracks visible on the outside?

To make a decent repair, all the plaster & render base has to be removed at least 200mm either side of the crack to asses how bad it is. The repair itself generally involves fixing stainless steel reinforcing mesh overlapping the crack by 150 -200mm either side, re-rendering out to the surrounding wall level & then re-skimming the entire wall so you won’t see the repairs. Success rate is high but there is no guarantee the crack won’t open up again if the wall is still on the move.

Hi,
Forgetting the crack in the wall would I be able to repair any of the broken skim using the finishing plaster that I mentioned?

Although some manage it (you have to start somewhere), using Finishing plaster is not really a DIY proposition. It’s not particularly easy for the inexperienced to use & can be difficult to invisibly “blend in” even for a pro; I always prefer to re-skim the whole wall as, in reality, its mot much extra work. You could use a one coat plaster which is more DIY friendly but I find it doesn’t give a particularly good finish &, personally, I don’t like it; Easyfill may be a better option for you. With a lot of filling, sanding & patience you may get a reasonable finish but you will generally be able to see the joins & it will never look as good as a properly repaired & re-skimmed wall.

Hi,
I presume a plasterer would not be too keen on removing wallpaper paste and I would rather do this time consuming job rather than pay someone, but a lot of the filler on the walls is proud hence I have been using a chisel to remove to get it flush, do you think its best to stop doing this then?

No he (probably) wont want to remove the wall paper & you can go some way to removing proud filler but make sure it’s well stuck to the wall or it will have to come out. As I said, don’t do any other filling or prep work without consulting your chosen plasterer first as using the wrong materials & inapropriate repars may actually create more work.

 

[bathstyle]

Richard,

I nearly suggested the Galvanised mesh method, this really is the proper way to do it, I agree with it, although, as mentioned, assess the wall properly first, the scrim tape could well provide the correct repair as quite often sand/cement render has large cracks in it.

I have used the scrim repair quite often in the past, in partular in situations where the render coat has been applied too thinly and the thick mesh cannot be used.

 

[Richard C]

Richard,

I nearly suggested the Galvanised mesh method, this really is the proper way to do it, I agree with it, although, as mentioned, assess the wall properly first, the scrim tape could well provide the correct repair as quite often sand/cement render has large cracks in it.

I have used the scrim repair quite often in the past, in partular in situations where the render coat has been applied too thinly and the thick mesh cannot be used.

Scrim will work if the crack is restricted to the fishing skim but with cracks of that nature, my experience is it’s through the base coat & often the blocks are cracked as well; local repairs & a large lump of reinforced mesh over the lot is the only cure in this case & even then it may crack again if the wall is still moving around.

 

[sunshine99]

Thanks for the suggestions , the crack is on the internal Party wall, it is where a Chimney breast once was and has been bricked/blocked up and rendered & skimmed

I'm no builder but would have guessed this crack is the where the edge of the new brickwork is (used to fill in the breast). I think it has settled and cracked the render and skim.

I've removed some of the skim coat and the crack is in the render too, although not as wide, only about 2mm

 

[bathstyle]

You are quite correct in your advice Richard, a scrim tape just wont do.

In Germany they seem to use a kind of rubbery plastic mesh as part of the complete render, I thought this was a good idea as it would posssibly stop any problems of this nature. It covers the complete wall.

 

[bathstyle]

Thanks for the suggestions , the crack is on the internal Party wall, it is where a Chimney breast once was and has been bricked/blocked up and rendered & skimmed

I'm no builder but would have guessed this crack is the where the edge of the new brickwork is (used to fill in the breast). I think it has settled and cracked the render and skim.

I've removed some of the skim coat and the crack is in the render too, although not as wide, only about 2mm

I would be quite tempted to run a grinder down either side of the crack and knock the reder off to examine the brick/block behind it. Then as mentioned mesh and re render then skim

 

[NickB_99]

I would be quite tempted to run a grinder down either side of the crack and knock the reder off to examine the brick/block behind it. Then as mentioned mesh and re render then skim

Have used a Stanley knife to cut back undercoat plaster in the past. Would this work with render (or is it too hard?)

 

[bathstyle]

No way, a grinder or hammer and bolster or drill with hammer action only

 

[Richard C]

I would be quite tempted to run a grinder down either side of the crack and knock the reder off to examine the brick/block behind it. Then as mentioned mesh and re render then skim

That's your next move but I usually do it by hand using a hammer & bolster chisel. An SDS breaker creates a lot of vibration &, on an old wall, this can loosen the surrounding render & even cause further cracks to open up in the mortar joints.

Another method I’ve used if the wall is cracked & I think the chance of a successful repair using mesh would be limited is to first repair the crack with mortar, dot & dab a complete sheet of 12mm plasterboard centrally over the crack & tight to the wall, then dot & dab out the rest of the wall, tape & skim. You loose about 15mm but if the crack does open up in the wall again it won’t transfer through to the PB - if you’re lucky.

 

[bathstyle]

Nowt wrong with a grinder and hammer and bolster or will someone pop their head into this thread and complain that the grinder uses electricity so should be avoid 'coz of the environment

 

[roughcaster]

You shouldn't use a grinder because it uses electricity and creates a lot of dust and noise, and is not very kind to the environment,,, there, i've said it,, do i agree with it?,,,, do i *******s,, grind away, but wear a mask/goggles,,, (ooops, i nearly said condom too,, but that's a different type of grinding)

Roughcaster.