URGENT!!!!!!!!!!!!!!!!!!!!!!!!!!! - hardwall on solid brick walls

[Porthole]

Hi there

Be really grateful for your comments on this- am having MAJOR panic!! We have a 1930s house with solid brick walls (no cavity). The builder has hardwalled half of the house applying PVA first I think. But we have just read about how hardwall would not be the first choice for solid brick walls due to damp penetration. This is a major blow for us as half the house has been done and they are in the process of slapping more onto the walls tomorrow. Can anyone tell me whether we should stop them in their tracks before they hardwall the whole house? If it is not good news, we were thinking maybe we could use the Limelite brick and stone protector which reduces the amount of water absorption by the bricks by 98% if used on the outside of the house. The reason the builder used hardwall is because there are some broken bricks and he says it helps to bind everything together. 

 

Our tiler has also said that he cannot tile onto hardwall in the bathrooms. He said he needed the walls to be dot and dabbed with moisture resistant plaster or skimmed. I am thinking that skimming is not that good an idea as I understand it takes 20kg per sq metre of weight and our tiles are on the borderline for this. Therefore maybe moisture resistant plaster is better. However, please can someone tell me how to apply the green plasterboard to the hardwall as presumably if this does not bond well to the tiles then it is no different from trying to stick the tiles to the hardwall directly.

 

Would be really grateful for your comments ASAP, as this is a bit of an urgent issue. We have bags of hardwall up to the ceiling in some of the rooms so I need to know if this is the correct stuff to do.

 

Thank you soo much!!!!!

 

 

 

[Temp]

I've no experience with Hardwall and single skin brick. Is it rendered outside?  Google finds comments recommending sand and cement instead. Personally I would be fitting internal wall insulation. I doubt PVA is the best to seal with either if there is any damp. 

 

https://www.plasterersforum.com/threads/hardwall-on-external-walls.37045/

 

"i rang british gypsum today to confirm what i already knew. they told me that you can use hardwall on solid 9" external walls only if they are dry, hardwall did replace renovation plaster as they were basiclly the same. they also recommend dri coat for solid walls that have had a damp course injection."

 

"ya but the problem is there solid walls...they are prone to damp, how good is the render on the outside? or how good is the mortar? There is no cavirty... personally if i was asked to do a job like that, I would use sand and cement. No british gypsum product is waterproof. Also people tend to dab it with insulated plasterboards or batton it out. you could then bond and skim it."

 

https://www.diynot.com/diy/threads/plasterboard-on-one-wall-face-and-bonding-coat-on-the-other.383114/

 

"You've to be careful somtimes dot and dabbing onto a single brick wall. The same applies to using bonding or hardwall plaster. Providing you know there is "definitely" no chance of damp/moisture penetrating through the single brick from the outside, it'll probably be ok, but give the brick wall a sand and cement scratch coat first. Use a "measured amount of WATERPROOFER" in the mix.
Make the scratch coat: 4 to 1,,,, (4 of sand, 1 of cement) + the WATERPROOFER. Better to get someone who knows the job, to do it.
Another good way for you to go would be to scratch coat, and then batten the wall, put in some insulation between the battens, then plasterboard the wall with 12.5, foil backed plasterboard. That's the way i'd go on a wall like that."

 

 

[nod]

Hardwall shouldn't be applied on areas that are likely to get damp He would have been better with sand and cement waterproofer Or one of the renovating plasters such as limelight 

Your tiler is half right You probably would have been better with bare moister boards in the bathrooms But the weight rule for tiling doesn’t apply to solid skimmed walls in the same way as boarded walls 

So unless the tiles are 18 mil plus Tgey will be fine on hardwall 

[Porthole]

On 10/01/2022 at 06:40, nod said:

Hardwall shouldn't be applied on areas that are likely to get damp He would have been better with sand and cement waterproofer Or one of the renovating plasters such as limelight 

Your tiler is half right You probably would have been better with bare moister boards in the bathrooms But the weight rule for tiling doesn’t apply to solid skimmed walls in the same way as boarded walls 

So unless the tiles are 18 mil plus Tgey will be fine on hardwall 

Hello

Thank you for your response - giving me some hope. 

 

Please can I ask what the weight limit is for solid skimmed walls and where I can find this?

So, if we get them to skim the hardwalled walls, then we should be ok with our tiles which are around 20kg before adhesive, if they tile onto the plaster skimmed walls?

 

Thank you very much 

[nod]

As a tilling contractor we work off a maximum of 20 kg per m2 

As stated previous Once you get above 18 mil tiles They should be on sand an cement or a backer board 

[Porthole]

33 minutes ago, nod said:

As a tilling contractor we work off a maximum of 20 kg per m2 

As stated previous Once you get above 18 mil tiles They should be on sand an cement or a backer board 

Hi Nod, our tiles are 8 mm porcelain tiles which weight about 20 kg per m2, but after grout and adhesive of say 4kg per m2 we will be above the limit for plaster skim. They are pretty standard porcelain tiles (600 x600mm ) but sounds like they will be too heavy for plaster skim and we will need backer boards. 

 

Do you know if the backerboards can be stuck to the hardwall?

[nod]

They can

but would need to be mechanically fixed 

Gypsum do knockins 

[saveasteading]

1 hour ago, Porthole said:

Do you know if the backerboards can be stuck to the hardwall?

Good suggestion as it is also water resistant/proof. 

17 minutes ago, nod said:

Gypsum do knockins

If in any doubt you can plug and screw...even just at corners to hold it tight.

If knock-ins means hammer fixings then that should be fine, but I find they don't always pull as tight as plug and screw (prob if into mortar)

[Porthole]

 

 

16 hours ago, saveasteading said:

Good suggestion as it is also water resistant/proof. 

If in any doubt you can plug and screw...even just at corners to hold it tight.

If knock-ins means hammer fixings then that should be fine, but I find they don't always pull as tight as plug and screw (prob if into mortar)

Thank you very much. We are a bit concerned about attaching the backer boards to the brick wall behind the layer of hardwall as it would be impossible to see where the mortar lines are. During the course of the build, the builder has been telling us how hard the bricks are mortar are. Also, is there a chance that the bricks would crack behind the hardwall and we wouldn't be aware of that? What would be best fixings to go into very tough bricks if we cannot see where we are going in? Is it the hammer fixings you mention above, or can some kind of nail gun work? Sorry - I am not a tradesperson - just a homeowner so this is all new to me. Thank you once again.

[saveasteading]

3 hours ago, Porthole said:

is there a chance that the bricks would crack behind the hardwall

Not much. The important thing is to use a quality hammer-drill, as they will provide a smoother operation.

Also nice new hammer drill bits, with top brand names (de Walt, Bosch etc) as they are very much better at cutting rather than bashing.

Some may go into mortar, and you will know that because it will be softer and different dust comes out. Most will not, and once you know where the mortar bands are ,you can adjust to mis the rest.

I would also use stainless steel screws, as the dampness won't matter, but quality, coated screws should be ok too.

[Porthole]

23 hours ago, saveasteading said:

Not much. The important thing is to use a quality hammer-drill, as they will provide a smoother operation.

Also nice new hammer drill bits, with top brand names (de Walt, Bosch etc) as they are very much better at cutting rather than bashing.

Some may go into mortar, and you will know that because it will be softer and different dust comes out. Most will not, and once you know where the mortar bands are ,you can adjust to mis the rest.

I would also use stainless steel screws, as the dampness won't matter, but quality, coated screws should be ok too.

Thank you very much for your support on this