Drylining bedroom wall with insulated boards

Argo foc yourself · 29-12-2021 7:41pm #1

One wall of bedroom is getting a lot of dampness especially around the window reveal. The wall is north facing and insulation is almost non-existent.

The wall is cavity block. there is a vent in the wall and windows are opened almost every day.

My plan is to strip back the dry lining and slab with insulated boards. Rather than baton the wall I am planning to dot and dab all around the wall. Paint the rear of the insulated board with super PVA every 15cms to create a seal.

After that I need to secure to wall with mushroom fittings or these metal fixings???????

https://insofast.co.uk/insofast-products/insulation-fixings/plasterboard-fixing.html

Any suggestions greatly accepted. Am I doing this right or wrong?

Also Should I use the same insulated board around the window reveal or should that be a more narrow board?

GreeBo · 29-12-2021 11:07pm

Just mechanically fix the new boards unless the wall is very out of true, I'm not sure what the PVA is trying to do to be honest?

Also just do the external walls, no point in doing them all really.

Typically you use a thinner board around the window as the window frame won't be thick enough, but you can use whatever you are comfortable looking at.

Will you be finishing the room yourself? (Radiators, skirting, curtains, door frames, light switches, jointing & taping + potential skim + paint?

Argo foc yourself · 30-12-2021 9:40am

https://www.boards.ie/discussion/comment/118388866#Comment_118388866

many thanks for reply. It is just one wall in a bedroom. It is the only external one. It has a window and radiator below it.

I got a quote of nearly 2k to do it so I decided to give it a shot myself. the wall is approx. 9ft wide with window and radiator.

My plan to finish myself - tape, skim, sand, paint. curtains and skirting

The PVA was as per this lad suggests at 12.53sec

https://www.youtube.com/watch?v=UYTbMi2Jgfk

10-10-20 · 30-12-2021 9:49am

I used a wall adhesive foam in a can and then used nylon insulation fixings applied slightly above the recommended application rate. Steel fixings are normally recommended.

There are about 6 different wall adhesive products out there, all pretty much the same except for the price. I found that it cost a fortune if I applied the adhesive using the plastic straw which comes with some of the cans - you really need to invest in a gun and cleaner (about 35 EUR). Much less waste and it's 3-times easier!

When applying the adhesive to the boards, apply it in box or ladder shapes but don't fully join up the boxes - leave air-gaps, otherwise the boards won't sit tight and they expand back out from the wall after you initially set them.

But before you launch into this project you need to work out whether you have any damp issues with the "cavity blocks". Entrapping a whole load of moisture behind a vapour barrier and ~50mm of insulation is just looking for trouble otherwise.

darrencan1988 · 30-12-2021 9:49am

https://www.boards.ie/discussion/2058224885/drylining-bedroom-wall-with-insulated-boards

Would you think about getting the external wall done instead ? as it will help keep some size to the inside and its a great new finish on the outside with all the benifits plus you coulld use a smaller insulated board inside yourself then to help with keeping the heat in.

TimHorton · 30-12-2021 10:20am

https://www.boards.ie/discussion/comment/118389793#Comment_118389793

This guy is a DIY'er (He main job is installing blinds - he has just recently gone full time on Youtube) who runs a great channel and admits he makes lots of mistakes so by no means an expert.

MakersMark · 30-12-2021 10:24am

As mentioned, how will you stop moisture buildup behind the I splayed board?

This can turn to mould.

Argo foc yourself · 30-12-2021 1:43pm

https://www.boards.ie/discussion/comment/118389820#Comment_118389820

getting a lot of damp around the window reveal and sill.

Argo foc yourself · 30-12-2021 1:46pm

https://www.boards.ie/discussion/comment/118389822#Comment_118389822

yes I am planning on getting the external done also. I live in a semi detatched so three external walls. Front and side are cavity wall and have been pumped already. Rear wall (north facing) is cavity block. I intend to get the external cladding on that and insulated room from inside

Argo foc yourself · 30-12-2021 1:49pm

https://www.boards.ie/discussion/comment/118389940#Comment_118389940

em? I thought the moisture was a buildup of cold air hitting the warm plasterboard surface. There is little or no insulation behind the board currently.

Emma2019 · 30-12-2021 2:13pm

https://www.boards.ie/discussion/comment/118390944#Comment_118390944

If you're getting external done any time soom there would be no point in doing the internal and losing the space.

I'd say get a decent dehumidifier if you can in the meantime. Or put some anti mould paint around the windowsill.

Also make sure you're not drying any clothes in that room (or in the housen if you can avoid it)

10-10-20 · 30-12-2021 2:22pm

While I think that Charlie is a good inspiration for many DIY projects - in terms of the PVA guidance, do not use PVA as a bonding agent or dustproofer. The PVA is likely to reactivate under humid conditions and you don't know how that is going to work over time with the surface bond either with plaster dabs or with expanding adhesive. Buy a container of SBR in a builder's providers and water it down to 50/50 and use that instead to prepare the wall.

I also had moisture at the lower window corners and reveals. I re-insulated the reveals with a 27mm or 37mm insulated board, then skimcoated to about 4mm thick. You'll have to plan this part carefully as you need to maintain a bevel at the window, but you want to maximise the insulation too. You'll also have to deal with putting in the mesh angle-beads around the windows, if you take your time you can get this right, but I did find this the most challenging part.

BTW, when you said "cavity block" do you mean a twin leaf block wall with a cavity and insulation between, or what is the make-up of the wall?

Outkast_IRE · 30-12-2021 2:46pm

By cavity block i think he means just that - Single Leaf Cavity Block.

To be 100% honest in buildings with Single Leave Cavity Block i always tell people not to bother faffing about inside with dry lining and go straight for external insulation. You dont really put on internal insulation then put on external , you get no benefit of the thermal mass of the wall.

You are not addressing the root cause of the high level of dampness by drylining you are just covering it up , which can cause further issues in itself.

I assume you have checked everything on the external side is ok in terms of

Leaking Gutters.
Cracks or weaknesses in render ?
What is the finish on the outside sand and cement ?

In summary give the external side of the house a serious checkover for places water can infiltrate. Skip drylining get a temporary dehumidifer or install a simple Positive Input Ventilation system these can help in damp cases. Then start getting quotes on the external insulation its a much better job.

Internal insulation / Drylining is like putting on extra tee-shirts in the winter , yeah it keeps you warmer but there are gaps in the insulation everywhere. External insulation is like putting on a jacket much better solution to keep the heat in (Much more expensive too but worth it and it will eliminate the damp problem.

10-10-20 · 30-12-2021 2:50pm

Agreed. If it's a breeze-block then go straight to EWI.

Argo foc yourself · 30-12-2021 3:50pm

https://www.boards.ie/discussion/comment/118391180#Comment_118391180

9in cavity block

Argo foc yourself · 30-12-2021 3:56pm

https://www.boards.ie/discussion/comment/118391310#Comment_118391310

gutters are good.

render is sand and cement and all seems good. the wall is 9in cavity block then on the internal the slabs are suck to the wall with a bit of rolled insulation here and there.

Argo foc yourself · 30-12-2021 3:58pm

thanks as ever for all the comments.

C. Eastwood · 30-12-2021 11:00pm

https://www.boards.ie/discussion/2058224885/drylining-bedroom-wall-with-insulated-boards

Argo foc yourself.

You have a problem and it may be a simple problem or a difficult problem.

I am not DIY’r and I’m not a Handyman.

You can accept or reject my advice.

You have been given some good advice, and you have been given ridiculous off- the-wall advice.

My advice is to retain a Registered / Chartered Building Surveyor to diagnose exactly what is causing the moisture on the inner face of the external Wall, and to carry out the remedial works

You have confirmed that your external wall is a 225 mm Cavity Block Wall (Hollow Block Wall).

Your house if it’s constructed in Dublin may be a newer vintage, if it’s constructed elsewhere it may be a 60’s wall.

If it was constructed in the 60’s it was probably built by a qualified mason. The only thing that the mason had to do was put in a DPC at Floor level, and the outside ground was usually 225 mm below the floor level. (Probably 😋😷)

The first thing you need to do is ascertain is the dampness at window level caused by either (A) Condensation Mould Growth or (B) Ingress of rainwater at the window level or (C) Both of these.

Ensure rainwater is not getting in around the window frame

Both of these are Dampness problems with totally different causes. A Building Surveyor will ascertain which of the above is the cause with a Surface moisture meter and a moisture meter with penetrating pins.

If there is Ingress of rain water - you will have to stop the penetrating moisture.

If it is caused by Condensation Mould Growth there will be dark black/ olive green mould growth on the wall.

there will also be a musty odour and the mould growth will possibly form behind curtains and headboards and pictures. Some of the curtains may be tearing

See the 2 photos here

0883DAEB-4AF6-4CBE-9742-521AA9291CE9.jpeg

FA644B90-22B6-4E07-8471-BA1FD3531485.jpeg

Wash it off with a cloth dipped in 1part bleach to 4 parts water, and dry the surface. (Wear Eye Protection).

Then fit Insulated slab which I will discuss below.

You have not mentioned dampness in the wall as floor level, if this is correct then it is not rising dampness.

If the dampness at the window is caused by ingress of rain water, then the moisture passing through the wall will cause Efflorescence Salts which are white salts and will push the paint off the inner surface of the wall. See 2 photos

EEDC0AF9-EAAA-44BC-A6F4-71E8CA35E653.jpeg

477E30BF-77AA-4A7F-BB22-643F7620A7E8.jpeg

Give a detailed look at the external plaster on the wall and look for any cracks that will allow rainwater to penetrate the plaster.

Are these salts apparent on the inner surface of the wall?

If it’s Just Condensation Mould Growth do the following:-

Remove all the existing Drilining and batters from the wall. If there is no Dry Rot or Wet Rot (moisture or fungus or discolouration) in the battens then there is no ingress of rainwater dampness in the wall.
Whoever is sleeping in this room is in a very damp environment with mould spores in the atmosphere, and is living in a very unhealthy environment.
You have received advise to:- get a dehumidifier; use anti- condensation paint ( Zinsser is the one) and advice about adhesive.
This is a waste of time and money. You would be better off having a meal and drink with the money.
You must solve this problem asap and correctly.
If you use adhesive on the existing paint on the wall, the paint on the wall can barely hold itself on to the wall, and may pull off the wall with the adhesive and the weight of the slabs, and is a waste of money.
Everything in a building is fitted by either Chemically or Mechanically, and sometimes both.
Fix (mechanically) the Insulated Slabs with nylon insulation mushrooms. No need for adhesive. Phone manufactures for number of fixings per slab. see photo.

B4C08C65-029B-46C9-81DF-426E316F4C88.jpeg

Do not use metal insulation mushrooms. In an uninsulated cavity block wall, metal fixings are a cold bridge and you will get condensation mould on the surface of the plaster at the metal heads.
To be in compliance with the current Building Regulations for fitting insulation on an existing external wall of a dwellinghouse you need to attain a U Value of 0.35 Watts/m2/degree C/hour.
The U Value of a cavity block wall is approx 2.1 Watts/m2/degreeC/hour
The Building Regulations have 5 purposes:- 3 are for the Health Welfare and Safety of persons.
So stick with the Regs. Phone any of the insulation companies and ask to speak to a Technical Person - tell them the type of wall and the U Value must be 0.35. They will give you excellent free advice.
The thickness of the Insulation will depend on the K value of the insulation ( don’t bother about this)
you will possibly be using a plasterboard slab with approx 65 mm insulation.
Check the two other walls/partitions of the bedroom. Tap them with your hand to ascertain if they are stud partitions or 100 mm concrete block partitions walls.
if they are internal concrete block partitions, and are connected to the external cavity block wall- then they will be cold bridges, and the Condensation Mould Growth will form on these walls, near the the external wall.
Therefore you will need to insulate these partitions with a slab with approx 25 insulation. I would insulate the entire partitions as I would not tolerate a step in a wall.
You can only fit a slab with a few mm of insulation on the 2 side reveals and the soffit reveal (top) around the window frame, as much as possible to fit there
only use plastic Angle beads around the window reveals - do not use metal.
This will cost you money and therefore get advice from a Building Surveyor before doing anything.

Regards C Eastwood.

Argo foc yourself · 31-12-2021 10:54am

https://www.boards.ie/discussion/comment/118393938#Comment_118393938

Wow. A lot of information there. I am going to have to sit down and study this more. thanks for all that info.

My problem is more akin to your second image. I spray it with Astonish Mould and Mildew Blaster and it disappears - for a while.

I don't see any defects outside. The house was built in 1997. There is no problem at floor level and the room in question is upstairs

10-10-20 · 31-12-2021 11:09am

Built in 1997 - then it's a double-leaf wall possibly with partial-filled polystyrene insulation in a 100mm cavity?

C. Eastwood · 31-12-2021 2:01pm

https://www.boards.ie/discussion/comment/118395141#Comment_118395141

Thanks Argo foc yourself- for your comments. You have stated that the wall in the photo is a hollow block (225 mm Cavity Block constructed wall) built in 1997. These walls are constructed in Dublin today, and are acceptable by Homebond and all details of the construction of same are given in Homebonds House Building Manual.

If this is the only condensation mould growth in the bedroom then it is a mild problem of condensation. The best paint to prevent condensation mould growth is Zinsser.

You stated that the wall is insulated on the internal side. The Technical Guidance Document L (TGD) 1991 of the Building Regulations were the regulations in force at that time. These were replaced by the 1997 TGD, but I assume the builder was able to use the 1991 document. Therefore with the 1991 TGD L - which is one of the 5 purposes of the Building Regulations which is the “Conservation of Fuel and Energy”.

The U Value require by this TGD is 0.5 watts/m2/degreeC/hr. This is a very good maximum U Value and your house should (hopefully) be in compliance with the 1991 TGD.

You said the room is approx 9 ft long.

Therefore the external wall is approx 2.7 m x 2.4 m = 6.5 m2. Take out 1 m2 for the window = the wall is approx 5.5 m2 of wall.

Assume a temperature of today outside of 10 deg Celsius and a temperature in the bedroom of 20 deg C. Then the heat loss loss through the wall is as follows:-

0.5 watts/M2/difference in degC/hr.

0.5 watts x 5.5 m2/20-10/ hr = 0.5x 5.5x 10 = 27.5 watts/hr heat loss. X 24 hours = 660 watts heat loss per day.

Obviously with an outside Temperature of -1 deg C in winter the heat loss would be approx double that -

0.5 x 5.5 x 21 = 57.5 watts/ hour heat loss. = 1,386 watts heat loss per day.

This would be a very good insulated wall.

With 225 Hollow Block walls sometimes the builders use a 225 wide precast lintel over the window ope and this is very dense concrete and is a very cold bridge.

It appears that this may be your problem and that this cold bridge is not insulated correctly and you may only need to fit an insulated slab on the 3 window reveals- a slab with as much insulation as the window frame allows.

Ventilation Is very important in reducing Condensation.

The other very important thing to reduce Condensation Mould Growth is to reduced the amount of moisture in the atmosphere in the house as follows:-

Don’t dry clothes on radiators,
Fit mechanical extractor in the shower/ bathroom and kitchen. Must be exhausted to the external air. Must never be exhausting in the the attic void.
After a shower/ bath - switch on the extractor, or before you leave - open the window and then close the bathroom door behind and allow the moist air created to escape.
When cooking/ creating steam - turn on the extractor and open window. Close the kitchen door to prevent moist air escaping in to the other parts of the house.
As I said it’s best to engage a Building Surveyor to carry out a survey of the problem. It may cost a few hundred euro but it could save you from carrying out any unnecessary expensive works.

dathi · 01-01-2022 12:03pm

Do not use metal insulation mushrooms. In an uninsulated cavity block wall, metal fixings are a cold bridge and you will get condensation mould on the surface of the plaster at the metal heads.

Additional mechanical fixings should be provided to each board applying a minimum of 2 metal fixings, after the adhesive has set, in accordance with BS 8212:1995 and manufacturer’s instructions.

taken from xtratherm insulated plasterboard agrement cert which must be complied with, but i could have taken it from any manufacturers cert

C. Eastwood · 01-01-2022 2:54pm

https://www.boards.ie/discussion/comment/118399868#Comment_118399868

Good Man dathi.

I am shocked at the amount of critics on this site, that all they can do is to give criticism when substantial free advice is given to people looking for help. And the last thing they ever do is give any good practical advice to persons requesting it.

I note the absence of any advice whatsoever given by your good-self to Argo foc yourself.

It is difficult to explain to clients, especially after they have spent a considerable amount of money on having their house insulated with internal drilining, why their new painted wall is covered in dots of condensation over the heads of the metal mushroom fixings. Now that I have your contact details daithi, I will get you to call to the clients and you can give the British Standards and all the Manufactures Instructions chapter and verse to them, and they will be so happy with their black condensation dots on the wall.

In renovating or refurbishing an existing building, the Irish BR - TGD’s states “as far as is practical” - therefore the Certifier must use his Training, Knowledge and Experience and Expertise in giving the client the best job as is possible in accordance with the Building Regulations.

In deciding to use either Nylon of Metal fixings, or both - on an existing or new external wall, the U Value of the wall must firstly be ascertained and the possibility of any “Cold Bridges” must be ascertained, and eliminated.

The Concrete Hollow block, which does not have a complete cavity, is a cold bridge and Stainless Steel Insulation Mushroom Fixings are also a cold bridge. Put the two of them together and you have an excellent Cold Bridge that will conduct cold from the outer face of the wall to the inner face of the wall, and will definitely cause Condensation Mould Growth.

If there is a concrete block - cavity constructed wall with any insulation in the wall - say a wall built in 1978 with 25 mm of polystyrene on the outer face of the inner concrete block- then I would specify that all drilining is to be fixed to the inner face of external walls with stainless steel insulation mushrooms fixings, because there is no cold bridge (because of the cavity) and because metal fixings are far easier to install.

I would specify some metal mushrooms at higher level in a concrete block cavity constructed wall with no insulation, there is no doubt whatsoever that there will be mild black condensation mould growth apparent on heads of these in the Kitchen and Shower Rooms. This will be mild and is easy to clean of with a damp cloth

I would not use metal insulation mushrooms under any circumstances in a hollow block constructed wall because the U Value is approx 2.1, and condensation mould growth will definitely form on the painted plaster surface over the heads of the mushrooms.

The purpose of these 2 metal fittings (as per your BS) is to keep the insulated slab fixed to the wall in the event of a fire, because the nylon mushrooms heads will melt and the slabs may fall off the wall. This will take well over 40 minutes.

In a fire people will be dead in a few minutes from Carbon Monoxide poisoning. With their House Insurance all the fire damage slabs must be replaced.

Manufactures specify belt and braces. Using adhesive on a painted wall is a waste of money as the paint will detach from the wall surface with the weight of the adhesive and insulated slab and plaster.

Specifiers in Remedial Construction works of existing dwellinghouses may do so “as far as is practicable.

I hope that the above highlights that - “Possession of a little knowledge is a very dangerous thing “.

This is the reason why I always recommended to people to retain an expert to look at their situation. If the problem is with a building- then engage a Chartered Building Surveyor to carry out a survey and to prescribe correct necessary remedial works.

Best of luck as a Critic dathi, and my last comment to you is the name of the person at the top of this thread who poster the query.