Painter used gyprock filler to fill gaps in old concrete wall

[ubonr1971]

I'm renovating an old building that has concrete walls and ceilings. The electrician removed all old wiring and the old switches (which were inside the wall) and thus there are subsequently holes everywhere. I was away a few days and have returned to see that they have used gyprock filler to fill all the old holes etc. Its the one that you can buy in homepro in power form and they mix with water. Usually used on new gyprock jobs to smooth things over. 

 

Last week I told him to use concrete but he evidently had different ideas. 

 

Will using the gyprock/ plastering mix do the job achieve  the same end result. Any problems with his methods as opposed to using concrete and a silicon gap gun?

 

thanks

[lopburi3]

Suspect will be fine - that's what I use (wall putty) but are you sure you have concrete walls?  They are not at all common here as construction uses support concrete poles and walls are normally non supporting brick/cement block so easy to remove or change.   

[ubonr1971]

3 minutes ago, lopburi3 said:

Suspect will be fine - that's what I use (wall putty) but are you sure you have concrete walls?  They are not at all common here as construction uses support concrete poles and walls are normally non supporting brick/cement block so easy to remove or change.   

Im unsure of exact structure but its as solid as a rock as they say. 

[Morakot]

Quote

Will using the gyprock/ plastering mix do the job achieve  the same end result. Any problems with his methods as opposed to using concrete and a silicon gap gun?

 

Mixing cement-based material with gypsum-based material can pose a considerable problem! The reason is that concrete cures in a fundamentally different way than gypsum; chemically speaking, cement-based concrete releases water, whereas gypsum retains it.

 

Depending on the size of these gypsum patches, your options for the wall finish can now be considerably limited. You cannot skim coat over it any more with anything another than plaster of Paris (gypsym). This in turn affects your choice of paint.

 

Having said this, there is nothing wrong with gypsum plaster on masonry walls as a top layer. In fact I have several indoor wall in my house here in Thailand with plaster of Paris and it is a beautiful, durable material that nicely regulates humidity. You may however find that local builders may not know how to properly work with such plaster.

 

 

Edited February 7, 2020 by Morakot

[bankruatsteve]

If the wall has been rendered, the filled holes are likely to be "shiny" after painting.  But, are you going to re-wire?  Cut new holes then?

[ubonr1971]

24 minutes ago, bankruatsteve said:

If the wall has been rendered, the filled holes are likely to be "shiny" after painting.  But, are you going to re-wire?  Cut new holes then?

it hasnt been rendered. It had wall paper on it before. Stripped it off with water and took out old electric wiring. As said above the old holes from the switches were inside the old cement wall. Now its full of gypsum. 

 

Have they stuffed it up or can a primer go on it after sanding. the member above 'morakot' suggests its an issue. What do you think about his comments?

 

[ubonr1971]

1 hour ago, Morakot said:

You cannot skim coat over it any more with anything another than plaster of Paris (gypsym). This in turn affects your choice of paint.

I dont understand your comment actually. The gypsum patches are in some spots where gaps have been filled etc. Its not all over. I cant see why this cant just be sanded along with the existing concrete walls and then painted with a waterbased primer. I dont understand your first sentence. 

[sometimewoodworker]

1 hour ago, ubonr1971 said:

it hasnt been rendered. It had wall paper on it before. Stripped it off with water and took out old electric wiring. As said above the old holes from the switches were inside the old cement wall. Now its full of gypsum. 

 

Have they stuffed it up or can a primer go on it after sanding. the member above 'morakot' suggests its an issue. What do you think about his comments?

 

No problem at all. You will have a different texture but no problem. A waterbased primer may not be the best choice, though if you first paint the patches with ½ lb cut of shellac you can use the waterbased finishes as the shellac will effectively seal the surface.

[ubonr1971]

1 hour ago, sometimewoodworker said:

No problem at all. You will have a different texture but no problem. A waterbased primer may not be the best choice, though if you first paint the patches with ½ lb cut of shellac you can use the waterbased finishes as the shellac will effectively seal the surface.

Thanks for your reply. Ive never heard of shellac paint. I looked on the homepro site and they said: 

'

Shellac primers: $40 to $63 per gallon. Excellent at blocking stains, shellac primer works well on walls that are susceptible to water or smoke damage.

Though all three primers can be used under latex paint, it's best to use a latex-based primer for a latex paint, oil-based primer for an oil-based paint, and shellac primer for walls with stubborn stains.'

__________________

 

So, are you saying that I should spot paint the shellac paint on the gypsum areas of the walls and ceilings only? And then let that dry and then put the standard water based primer coat on all areas of walls and ceilings after?

 

 

[Morakot]

 

5 hours ago, ubonr1971 said:

I dont understand your comment actually. The gypsum patches are in some spots where gaps have been filled etc. Its not all over. I cant see why this cant just be sanded along with the existing concrete walls and then painted with a waterbased primer. I dont understand your first sentence. 

 

As you are only painting this wall, the problem is merely cosmetic. I think, you will have a hard time to create a finish without the gypsum patches showing up. It's not a mater of sanding it down, but using a paint that will apply like on the rest of the wall. It wont be a sterling result my option, certainly not with regular paint.

 

If you are not happy with your final paint job, sand down the entire wall and apply a thin layer of gypsum plaster all over the wall. But this means you cannot easily paint it. You may just have the gypsum plaster as the top finish, nice and white. If you want colour you can add pigments to the gypsum plaster. It's not too difficult but you need suitable tools to work with gypsum.

 

 

A potentially more serious problem would be plastering over the the gypsum with a cement-based plaster. Lumps of gypsum inside a masonry wall will cause the cement plaster to break over time.

Edited February 7, 2020 by Morakot

[sometimewoodworker]

3 hours ago, ubonr1971 said:

Thanks for your reply. Ive never heard of shellac paint. I looked on the homepro site and they said: 

'

Shellac primers: $40 to $63 per gallon. Excellent at blocking stains, shellac primer works well on walls that are susceptible to water or smoke damage.

Though all three primers can be used under latex paint, it's best to use a latex-based primer for a latex paint, oil-based primer for an oil-based paint, and shellac primer for walls with stubborn stains.'

__________________

 

So, are you saying that I should spot paint the shellac paint on the gypsum areas of the walls and ceilings only? And then let that dry and then put the standard water based primer coat on all areas of walls and ceilings after?

 

 

First point shellac isn’t a paint. Second point don’t bother with the expensive “sellac primer” just get a Large container like this 

you do need to pay attention to the number. 

so in this brand, there are a couple of others that use different colour numbers, get 6, 8, or 3, you will need a gallon or two of alcohol, dilute the shellac 1 to 1 or 1(s) to 2(a) and paint everything. It’s incredibly fast drying so you could put on 5 coats in an hour if you wanted. If the gypsum is still soaking up the shellac just put on a few more coats.

 

the phonemail advantage of shellac is that it can be used over anything and everything can be used over it.

 

you probably want to use a primer, water or oil, over the shellac just to get a solid colour base.

 

don't forget to have excellent ventilation as you really don’t want to be breathing the alcohol fumes, if you cannot ventilate get a mask with organic filter cartridges.