Preparing a wall for plasterboard etc.

[tfman]

Hi,

I live in a Victorian terrace house (built around 1840) and I am currently re-doing to bedrooms on the top floor.

I've removed all of the old plaster and lath, so that it is now back to the brickwork. I've also had the rendering on the outside sorted out, as this was shot and causing penetrating damp. I'm now waiting for the wall to dry out before I start to decorate the wall. I just want to double check what I plan to do is sensible.

At the moment the plan is to

1) install a layer of insulation boards, either bonded or screwed into the walls.

2) install some batons for securing the plasterboard and future fixings,such as curtains

3) Plasterboard

4) Skim coat of plaster

5) Various finishing touches, such as paint, curtains and skirting board

I plan to do most of it myself, with the exception of the skim of plaster where I will get a professional.

I just want to check that this is a sensible plan of action? Have I missed any important steps. There is no pipe work or electrics on this side of the room, so that is not an issue.

I also have the following questions

1) The pointing is not looking in great shape. For the most part it is okay, but in some parts is completely deteriorated. Should I get this sorted out, or is it not a big issue? Is this a job for a professional? Or is it a reasonable DIY job?

2) What is the best order of installation for the insulation boards and the batons? For example, can I put the batons on the outside of the insulation board, with the fixings going through the baton, insulation board and then into the masonry? Or would it be better to have gaps between the insulation boards where I put the batons?

Thanks in advance for any advice.

 

[foxhole]

If the outside is rendered where the pointing need doing?

 

[tfman]

The outside of the wall is rendered, but the inside is currently bare brick. Some of the pointing (maybe I'm using the wrong terminology) between the bricks on the inside of the wall is a bit worse for wear.

I was just wondering whether this needs to be addressed, or whether I can leave it as it is.

 

[jay679]

As long as the pointing isn't horrendous (ie bricks loose or falling out), then just leave as is.
For insulation, create a studwork, infill with insulation, possibly a vapor control layer, then plasterboard - like this....

http://www.superhomes.org.uk/resources/insulating-a-solid-wall/

 

[tfman]

OK, great. That is good to know about the pointing. Also, thanks for the link. It is appreciated.

Just to double check, the vapour barrier goes between the insulation and the plasterboard? The link you highlighted wasn't particularly clear on this point.

Also, it states that there can be no tears in the vapour barrier. I presume I have to install the vapour barrier over the insulation, but not over the timber studs? What is the best method to achieve this? I presume masking tape and staples will suffice?

Thanks again.

 

[foxhole]

Vapour barrier passes over studwork, just a few stable to keep in place, any accidental tears can be taped with foil tape.Does not matter the barrier is pierced on studs as the plasterboard forms a seal along the stud.

 

[tfman]

OK, great. That is good to know.

Thanks for all the help. I'll give it a go once the wall have dried out properly.

 

[BigIan]

Hi,

As you have a victorian house, you more than likely have little to no cavity, also highlighted by your damp issues.
The issue with upgrading your insulation in these walls is that they are "brethable" often built with lime mortar and brick with a much higher level of capilarity (how watter is drawn through the brick) than modern bricks. Essentially this wall is going to have water in it some where and if you prevent this moisture percolating out internally as it will want to do due to the temperature differential your going to risk damp forming within the structure which may begin to rot any joist ends in the wall or the timber studs you've used to fix the plaster board too.

You need to be very carefull of how you specify this project taking care on selectibg the correct materials. English heritage have some handy information here

https://www.google.co.uk/url?sa=t&s...KKZ6FDWS2cZNsVyvQ&sig2=lPmSjvZTMFWN5VdZjwVa7g

With regards to your pointing, while you have this exposed why not patch those parts that are concerning you? Its good practice if youve never done it before.
Use a 4:1 mix of sand to lime.

Hope that helps

 

[tfman]

Hi Biglan,

That English Heritage leaflet looks very useful. I wish I had seen it before!

I actually had external wall insulation installed when I had the front of the house redone. Sorry, I should probably have mentioned that before, but I didn't think it was relevant. It is just a standard EPS system with a coat of render on the top.

I thought this was the standard. However, that leaflet indicates that the external wall insulation should be breathable for solid wall constructions, and the EPS systems are not breathable. It's too late now, but do you think I should have gone for something different?

In terms of the internal wall insulation, I thought I may as well install some of that while the walls are down to the brick anyway. Do you think this is worthwhile, or will it actually have some sort of detrimental effect? If I go for a permeable system, then would that be okay?

From what I've read the vapour control barrier is there to prevent condensation, which would occur when the warm moist air meets the cold wall. Is that right? As I have external wall insulation anyway, so that the walls will be warm themselves, I suppose that this is not so important?

Thanks again.

 

[BigIan]

I thought this was the standard. However, that leaflet indicates that the external wall insulation should be breathable for solid wall constructions, and the EPS systems are not breathable. It's too late now, but do you think I should have gone for something different?

To be honest It was and probably still is "standard" to most builders but there are breathable external insulation / render systems out there I believe Knauf do one and possibly STO as well.

In terms of the internal wall insulation, I thought I may as well install some of that while the walls are down to the brick anyway. Do you think this is worthwhile, or will it actually have some sort of detrimental effect? If I go for a permeable system, then would that be okay?

One of the issues with internal insulation even a permiable one is that it has the effect of "cooling" the brickwork, these bricks have stood for 175 years with the bricks being heated from inside, aidng them to keep dry. If you suddenly take away that heat yet the bricks are still moist you can risk significant frost damage.

From what I've read the vapour control barrier is there to prevent condensation, which would occur when the warm moist air meets the cold wall. Is that right? As I have external wall insulation anyway, so that the walls will be warm themselves, I suppose that this is not so important?

A vapour control layer (VCL) is there to prevent the moist warm air that is prevelent throughout a dwelling finding its way into the actual fabric of the wall (I.E all the tiny holes in the bricks and mortar) where it will then condense forming liquid warer that can then freeze and expand cracking bricks, or fid its way to timber elements and causing rot or fungal attack.

In all honesty a VCL is Incredibly hard to retrofit effectively on an existing building because

1) unless you comepletely gut the house and re hang joists etc there are far to many airgaps to make it worthwhile I.E how do you form an effective seal between the ground and upper floors? what about the roof space?

2) if you do fit a VCL without adequately adressing where the moist air is going to go then you do risk setting your self up for condensation. this is why in new build properties that are built with VCL`s then they often have mechanical ventilation heat recovery systems fitted to manage the moist air.

 

[pinenot]

+1 to a lot of BigIan's post(s)
Certainly the addition of a non-breathable external layer (presumably the render applied was cement based) will change the moisture movement in the wall or walls, thereby changing a few of your considerations for upgrades.
Adding internal insulation sometimes dramatically affects old build solid walls, however you could say that the insulation on both sides would provide something of a balance and most probably creates an inert wall.
I have to wonder if the render you replaced was at all original to the wall(s), is there any evidence of this?
One thing I think would be beneficial now would be to dehumidify the affected wall(s) but this could not be achieved quickly. Venting the wall(s) top and bottom, would also do it (don't know if you'd like this) but would require a bit of design to hide the gaps, especially at the top of the wall(s) A baffle or pelmet arrangement has worked for me in the past, but should be screened to provide an insect barrier, I recently rented an apartment and it had a featured ceiling made with 35 x 35 or so, timber battens, fixed to the ceiling boards approx 50 mm from the wall, a sort of shadow gap, that sort of thing could be used.

As a footnote, just look at some of the past similar discussions/posts on this site and you can see just how many problems adding insulation can cause, seemed so simple at first eh! ...pinenot

 

[tfman]

Biglan, it seems that you think there are two alternatives. Either I don't use internal insulation, or I wait for the walls to dry out? I assume the later would take years, and so is not really an option?

Adding internal insulation sometimes dramatically affects old build solid walls, however you could say that the insulation on both sides would provide something of a balance and most probably creates an inert wall.

Perhaps a naive question, but what do you mean by an inert wall?

I have to wonder if the render you replaced was at all original to the wall(s), is there any evidence of this?

I don't think so. I had a damp and timber survey done before I got the rendering done, and the surveyor thought it was from the 1970's/1980's. He didn't mention any of these issues regarding breathable render, which was nice of him.

One thing I think would be beneficial now would be to dehumidify the affected wall(s) but this could not be achieved quickly.

What do you mean by dehumidify the affected wall? I was planning to leave the wall bare for a while, to let it dry out a bit. I also have a dehumidifier, for an unrelated reason. Do you think that would help at all?

When the original rendering was hacked off, the external face of the wall as pretty wet where the rendering was shot.

Venting the wall(s) top and bottom, would also do it (don't know if you'd like this) but would require a bit of design to hide the gaps, especially at the top of the wall(s) A baffle or pelmet arrangement has worked for me in the past, but should be screened to provide an insect barrier, I recently rented an apartment and it had a featured ceiling made with 35 x 35 or so, timber battens, fixed to the ceiling boards approx 50 mm from the wall, a sort of shadow gap, that sort of thing could be used.

I'm not entirely sure what you mean here. Do you have an example, e.g. a website?

As a footnote, just look at some of the past similar discussions/posts on this site and you can see just how many problems adding insulation can cause, seemed so simple at first eh! ...pinenot icon_smile.gif

I'm glad I asked before I put up any internal insulation. Wish I had done the same for the external insulation! I did a fair amount of research before I got external insulation, and didn't see anything relating to these issues.

 

[pinenot]

It's not BigIan your responding to with this reply, it's me...pinenot.
Now to answer these questions -
1. An inert wall describes no moisture or temp movement
2. So you don't think render was part of the original build i.e. back in the 1840's, that's what I thought, and you have no idea what the 70's 80's render was made from (I'm guessing cement, which doesn't breath) so moisture was basically trapped inside the wall, hence the advice...dehumidify
3. But dehumidification of a solid built wall some 185 years old will take some time therefore the idea of creating a positively vented wall (open top and bottom to allow a venting of air over a year at least) No this would not mean you couldn't use insulation, but it would not be as you're currently envisaging.
4. Yes you've opened up a can of worms, but alls not lost, so let's go back to your original post.

You state that your waiting for the wall to dry out, this will likely not have come from the shot and now replaced render, the thickness of the solid build walls would prevent that, moisture penetration would be in the region of 4" - 6" at best. Is the roof covering (tiles/slate/shingles) in good order or has this been altered from the original? being the upper floor water could be soaking in hear, perhaps for a long time.
This is a good site for your type of situation - http://www.heritage-house.org/pages/managing-damp-in-old-buildings.html take your time reading it and come back with any questions you may have after that...pinenot

 

[tfman]

Hi pinenot,

You state that your waiting for the wall to dry out, this will likely not have come from the shot and now replaced render, the thickness of the solid build walls would prevent that, moisture penetration would be in the region of 4" - 6" at best.

When I had the damp and timber survey done, the surveyor stated that there was some `patchy areas of surface dampness' detected. In other words, it was not on the whole wall. All of the front rooms had damp areas in the same place, which was where the rendering was blown.

The report states that this is most likely caused by defective rendering and faulty rainwater goods. The hopper had a bush growing out of it when we bought the property. The faulty guttering meant the pretty much all of the water coming off the roof was splashing against where the rendering was blown. We have also now replaced the guttering, and this is now fine.

I am awaiting the arrival of a moisture meter, so I can also start taking some readings myself soon.

Is the roof covering (tiles/slate/shingles) in good order or has this been altered from the original? being the upper floor water could be soaking in hear, perhaps for a long time.

I went up to the roof when the rendering was done. It looked fine, no broken tiles or anything. I had some roofers around to do an (unrelated) job and they also thought it was fine.

We do have a parapet gutter, which I know can be a source of damp issues.

This is a good site for your type of situation - http://www.heritage-house.org/pages/managing-damp-in-old-buildings.html take your time reading it and come back with any questions you

OK, thanks for the link. I will have a look at it.