# Making concrete block wall airtight



## CBGB (27 Mar 2013)

I have a converted garage that is joined to my neighbours by a concrete block wall. My neighbours garage is being used as a garage and has no insulation anywhere and the wall is bare. On our side the wall was plasterboarded but the room is freezing. So I took some of the plasterboard down and I can feel the breeze coming through the block - both at the cement joints and also in the  main area of the block. I have decided to pull all the plasterboard down and fix the problem as the room is currently useless.  Any suggestions on how to make a concrete block wall like this airtight and warm? I know plastering is an option but can I then apply insualted boards on battens or dabs? Can I apply an airtight membrane before the battens? Any suggestions would be really appreciated. Also on any suggestions, do you reckon I could do it myself as a diy'er?


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## CBGB (27 Mar 2013)

Has anyone used airtightness paints such as this  http://airtightpaint.webs.com/faq.htm ? Sounds a bit gimicky.


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## Leo (27 Mar 2013)

CBGB said:


> Has anyone used airtightness paints such as this http://airtightpaint.webs.com/faq.htm ? Sounds a bit gimicky.


 
Sounds like a total gimmick to me. The only compare the air tightness of a block painted with this product to an untreated block. Why not compare it to one painted with a standard acrylic paint? I'm guessing it's very similar to normal acrylic paint, perhaps with a slightly higher solid percentage. So 2 coats of standard paint might perform better! 

Air penetrating through painted walls isn't a significant contributor to air leakage within a house. Focus on doors, windows, around skirting, sockets, etc. and don't waste money on paint!

You're probably just feeling the cold of the wall rather than an actual breeze through it, unless there are significant cracks. Use a smoke stick to trace drafts within the space and seal those. You need to insulate the wall. Are the floor and roof fully insulated? To what standard?


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## CBGB (28 Mar 2013)

Thanks for the reply. 

I only used my hand (wet finger test ) but it is definitely a breeze. You are right the plastering/cracks could be contributing but from what I understand these blocks can be a problem with airtightness. 
I rang a supplier (recommended on here - ecological buildings, I think) and he suggested using a scratch coat on the wall then mech fix an insulated slab. He said to ring insulated boards suppliers to confirm product ok with scratch coat under. 

The floors were insulated (100mm between suspended joists) and the roof is sloped with 100mm between rafters. My lovely builders also told me that they had insulated the wall I am working on but were lying through their teeth! Have since done a runner. 

Unfortunately I spent all my money on the conversion so cant pay anyone to come in so trying to do whatever bit I can to make the room liveable. Sure, we'll see.


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## p15574 (28 Mar 2013)

I have a similar problem and I had been trying to figure out where the wind was getting in. It seems to me to be down to the air vents. Taking off the inside vents, in the older part of the house,  these vents have a plastic insert, like a pipe, that allows the air to pass from outside to inside. In the affected area, however, there is no insert, just the outside vent, the inside vent, and the cavity wall in between, so the wind can circulates freely. For the moment, I have inserted some spare bits of insulation in a kind of circle around the area to block the cavity wall while leaving passage from outside to inside, but I plan to use expanding foam to seal it better, perhaps with a piece of plastic pipe in the middle for the air passageway.

Perhaps your problem is the same, and if you tackle how the draught is getting in, you won't need to be messing around with all the other insulation?


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## pwp (3 Apr 2013)

*Airtight Paint*

The company I work for produce the airtight paint that you are discussing. It is used and specified mostly on commercial projects because it is is quick to apply to large areas (up to 60m2 per hour), is airtight and is cost effective when compared to parging or plastering, or applying 2-3 coats of masonry paint over a few days. Our coating is often specified for walls that are subsequently going to have a plasterboard surface, architects realise that boarding alone is not enough to meet current airtightness regulations on commercial properties.

On a single garage wall you might want to use a standard locally available masonry paint, as application time is not a big problem for you, this will make a big difference to the airtightness of the room, provided you put enough on to fill all the cracks and small holes. Once applied, you will be able to see any larger cracks that need filling over the surface of the wall or at the edges. Another option is a parge coat, because although messy and slow it's not going to break the bank if you are applying it yourself. These are low cost ways to improve the airtightness of your garage and they will also reduce any noise transmission from next door (if thats an issue). Concrete block walls are extremely leaky, it's best to take them out of the equation altogether.

We are currently putting together some examples/tests to show the difference between our product and other products, such as a single coat of paint, 2 coats, 3 coats etc.


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## BarneyMc (3 Apr 2013)

I'll be putting natural stone on the front of my new build, the rest will be finished in a cement render.  Will this leave that side prone to air leakage and if so would a lick of this paint, applied to the external surface, before the natuaral stone is applied be good to use?  I'm aware that wet plaster applied to the inside surface of the external walls will help here also.


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## newirishman (3 Apr 2013)

Another option is to frame for drywall finish, and use spray insulation. That will give your an airtight seal as well as insulation.


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## BarneyMc (4 Apr 2013)

I don't want insulation on the internal side - the wide cavity beads will do that.  It's just to bring that wall up to the airtight level as the other walls that will be getting a concrete external render.  The internal will be ok with wet plaster, it's the outside layer that's the problem.


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## lowCO2design (7 Apr 2013)

newirishman said:


> Another option is to frame for drywall finish, and use spray insulation. That will give your an airtight seal as well as insulation.


show me Irish certification for this, please?


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## lowCO2design (7 Apr 2013)

BarneyMc said:


> I'll be putting natural stone on the front of my new build, the rest will be finished in a cement render.  Will this leave that side prone to air leakage and if so would a lick of this paint, applied to the external surface, before the natuaral stone is applied be good to use?  I'm aware that wet plaster applied to the inside surface of the external walls will help here also.


wide cavity , grey bead full-fill, with some stone external - new build, yeah? 

its the face of the internal block you want air-tight, you'll be using a plaster, and tapes at the junctions no doubt.


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## lowCO2design (7 Apr 2013)

CBGB said:


> Thanks for the reply.
> 
> I only used my hand (wet finger test ) but it is definitely a breeze. You are right the plastering/cracks could be contributing but from what I understand these blocks can be a problem with airtightness.
> I rang a supplier (recommended on here - ecological buildings, I think) and he suggested using a scratch coat on the wall then mech fix an insulated slab. He said to ring insulated boards suppliers to confirm product ok with scratch coat under.


 plaster the wall using air-tightness tape at the junctions.
when you  say converted, are you living in it? is this wall the boundary wall? is  your neighbours side of the wall dry i.e. is its internal, just not a  heated space? 


> The floors were insulated (100mm between suspended joists) and the roof is sloped with 100mm between rafters. My lovely builders also told me that they had insulated the wall I am working on but were lying through their teeth! Have since done a runner.
> Unfortunately I spent all my money on the conversion so cant pay anyone to come in so trying to do whatever bit I can to make the room liveable. Sure, we'll see.


does this extension comply with building regulations? have you had it signed off by an arch/eng? the joys of home extensions on the cheap..


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## lowCO2design (7 Apr 2013)

pwp said:


> The company I work for produce the airtight paint that you are discussing. It is used and specified mostly on commercial projects because it is is quick to apply to large areas (up to 60m2 per hour), is airtight and is cost effective when compared to parging or plastering, or applying 2-3 coats of masonry paint over a few days. Our coating is often specified for walls that are subsequently going to have a plasterboard surface, architects realise that boarding alone is not enough to meet current airtightness regulations on commercial properties.
> 
> On a single garage wall you might want to use a standard locally available masonry paint, as application time is not a big problem for you, this will make a big difference to the airtightness of the room, provided you put enough on to fill all the cracks and small holes. Once applied, you will be able to see any larger cracks that need filling over the surface of the wall or at the edges. Another option is a parge coat, because although messy and slow it's not going to break the bank if you are applying it yourself. These are low cost ways to improve the airtightness of your garage and they will also reduce any noise transmission from next door (if thats an issue). Concrete block walls are extremely leaky, it's best to take them out of the equation altogether.
> 
> We are currently putting together some examples/tests to show the difference between our product and other products, such as a single coat of paint, 2 coats, 3 coats etc.


lets see the IAB certifcation for this product or at least CE/EN certification relating to air-tightness? thanks


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## lowCO2design (7 Apr 2013)

p15574 said:


> I have a similar problem and I had been trying to figure out where the wind was getting in. It seems to me to be down to the air vents. Taking off the inside vents, in the older part of the house,  these vents have a plastic insert,* like a pipe,* that allows the air to pass from outside to inside. In the affected area, however,* there is no insert,* just the outside vent, the inside vent, and the cavity wall in between, so the wind can circulates freely.


 there you go! get the ventilation pipe/sleeves 



> For the moment, I have inserted some spare bits of insulation in a kind of circle around the area to block the cavity wall while leaving passage from outside to inside, but I plan to use expanding foam to seal it better, perhaps with a piece of plastic pipe in the middle for the air passageway.



_ insulation is not air-tight _


uncontrolled air-leakage is very different to fixed ventilation for us to breathe!
there are solutions, where you want to introduce a regulated ventilation supply such as [broken link removed](no connection btw)




> Perhaps your problem is the same, and if you tackle how the draught is getting in, you won't need to be messing around with all the other insulation?


? 

_insulation is separate to air-tightness - both are important and necessary, AND must be treated with respect._
insulation if installed in the wrong location or the wrong type can lead to mould and ultimately health problems, the same goes for a lack of fresh air-movement


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## pwp (8 Apr 2013)

Elite Airtight has been tested for airtightness by an independent laboratory in accordance with BS EN 12114:2000 - the information is available to see on our website


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## CBGB (10 Apr 2013)

lowCO2design said:


> plaster the wall using air-tightness tape at the junctions.
> when you say converted, are you living in it? is this wall the boundary wall? is your neighbours side of the wall dry i.e. is its internal, just not a heated space?
> 
> does this extension comply with building regulations? have you had it signed off by an arch/eng? the joys of home extensions on the cheap..


 

Thanks for the response - bit harsh and presumptuous there with the "on the cheap" comment. I can only put money that I have into an extension - got multiple quotes, all roughly the same, went with a recommended builder that sounded like they knew their stuff and paid an engineer to sign off. As a lay person what else can I do? Tried to do it by the books and have got consistently shafted along the way. Now I am out of money and trying to fix my house. 

On your other points, yes we are using the room as a utility and will use it as an extra bedroom when it gets fixed. The wall is the boundary wall with my neighbour. Their roof joins to ours - like a ^ shape (soory about poor description). Their room is not insulated as they use it as a garage. The doors are always open on their side so there is definitely a source of constant wind on their side.


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## lowCO2design (13 Apr 2013)

pwp said:


> Elite Airtight has been tested for airtightness by an *independent laboratory in accordance with BS EN 12114:2000* - the information is available to see on our website


can you post a link to these results and its certification, thanks. 

your website only gives a specification. NO link to the test results? or info on the independent lab?, or BBA?( without a BBA how do we know what applications it was tested and considered suitable for) there's no CE marking either (from June this year the product needs a CE Marking)


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## lowCO2design (13 Apr 2013)

CBGB said:


> Thanks for the response - bit harsh and presumptuous there with the "on the cheap" comment.


apologies
look at Siga* air-tightness products and plaster the wall wall along with using their tape at any junctions 

(*or equal approved product, Siga offer a 50 year guarantee - thats hard to beat)


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## John McClean (23 May 2013)

*Ventilation*



> there are solutions, where you want to introduce a regulated ventilation supply such as this (no connection btw)



Thanks Lowco2design for the demand control ventilation link, It seems a more cost effective way to meet your ventilation needs than a MHRV unit. Does this type of system meet the TGD part F?


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## lowCO2design (23 May 2013)

John McClean said:


> Thanks Lowco2design for the demand control ventilation link,
> 
> 
> It seems a more cost effective way to meet your ventilation needs than a MHRV unit.
> Does this type of system meet the TGD part F?









no it doesn't, in a new build MVHR is a better option and will show saying over the life time of the system subject to correct install of theright system and good air-tightness. (just because you saw report on a DCV companys website doesn't make it so)
yes, BUT again subject to you or preferably your architect  understanding what is required of part F and getting the DCV company to certify as such


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