9 inch cavity blocks in use?

Hi,
I purchased a second hand home built in 1999. Its one of about 80 in a housing estate. The house is a little cold and I started to look into insulation. When I opened by ESB box I was stunned to see a nine inch hollow cavity (2 cavity) block on its side. I also see the same 9 inch cavity blocks when I open air vents. Inside the walls are dry lines and insulated with rockwool or something similar.

I plan to drill a few holes to check the rest of the walls but given that the home is only 10 years old, I was wondering

1. Is it usual to see this type of block used? I thought that method of construction was from a bygone era.

2. Is there any effective way of insulating if it is 9 inch hollow blocks.

I'm hoping that the builder just used these blocks in places were there were planned vents and services (ESB , GAS etc) but Im not hopeful!

Any advice appreciated

Thanks

D

Hi DazzaMazza,

9'' cavity blocks are still being used particularly for extensions in the Dublin area.I have not seen them used in houses outside of Dublin.If you have checked a couple of wall vents and the block used is cavity blocks then the house is built from cavity blocks.Standard double leaf walls are 12'' thick so there would be no benefit in using 9'' cavity blocks in parts - it is usually one or the other.
The dry-lining of 2''x2'' battens with rockwool in between was the standard construction for 9'' cavity block houses.If you plan to up-date the insulation then you could remove your existing plasterboard.A rigid insulation board can be cut to fit tightly between the battens and then a thermal plasterboard fixed directly to the existing battens.For standard cavity walls the depth of insulation on the thermal board is advised not to exceed approximately .5 of the depth of the cavity wall insulation.I do not know if there are any restrictions like this for 9'' cavity walls - I shouldn't think so.
This amount of work will not come cheap.The insulation itself is expensive (Kingspan, Xtratherm , Quinntherm being the main ones) plus your affected electrical sockets will have to be extended and your affected rads taken off and then reset with some adjustments to pipework.Make sure and get a full quote for all the work involved before starting.Just don't get hung up on it costing a bit more to heat your house as it is as it may take several years to regain the cost of this refurb work.
Also check that there are no draughts from your windows.There is little point in having your walls toasty and a gale blowing in through the window as you won't notice the difference then.
Don't jump on the green bandwagon just for the sake of it.

Good post.

During the illusion that was the 'celtic tiger' cavity block construction became more and more common in developments outside of dublin. It was viewd by developers as being
1. quick in construction as more courses could be built in a day than double leaf,
2. not needing of any particular skill sets of workers, and
3. easily and quickly rendered due to the internal dry lining.

IMO this is a terrible form of construction.

Read this bimonthly edition of construct ireland magazine, in particular the article by Joe Little entitled 'breaking the mould'.... for a comment on just how dangerous this construction method is...

My house is about 15 years old and is constructed using 9 inch cavity blocks. It's poorly built, has vents (holes basically) in every room and we froze last winter. We have owned it for just one year. The temperature in the kitchen dropped by about 12 degrees overnight.

My original plan was to get foam pumped into the cavities. It seemed like a reasonable thing to do as our main issue is wind chill from air blowing through the blockwork cooling the walls (we have drafts blowing out of every orifice!). However this won't solve cold bridging, it may bring the dew point closer to the internal walls and there's no guraentee the foam will penetrate into all the required volumes.

The alternative for us (we don't think drylining is the way to go) is to externally insulate the entire house. Friends have had it done to their old corpo house and it worked well. It isn't cheap (about €100/m2) but there is an SEI grant available of up to €4k. We are waiting on our quote. The work will take one month to do apparently. We are having before and after BERs. Will update with more info as I get it.

sydthebeat said:

During the illusion that was the 'celtic tiger' cavity block construction became more and more common in developments outside of dublin. ...

Click to expand...

....only when done by Dublin-based developers, I should add.

Those blocks disappeared from use this side of the Shannon back in the early 70's. And of course, all this was de-facto condoned by the vested interests who managed to keep that block alive, from a Regs point of view. Should have been completely outlawed 30 years ago.

galwaytt said:

....only when done by Dublin-based developers, I should add.

Those blocks disappeared from use this side of the Shannon back in the early 70's. And of course, all this was de-facto condoned by the vested interests who managed to keep that block alive, from a Regs point of view. Should have been completely outlawed 30 years ago.

Click to expand...

while i agree with your second point, i must stress that it was not just dublin-based developers that built in this method 'outside the pale'...

i know one very large laois based developer company that built most of their extensive developments this way...

Thanks for the replies on this, much appreciated.

I cant believe that I have purchased a house thats barely 10 years old and made of hollow cavity block as I had assumed that this method was outlawed in the 60's. I had employed a surveyor who did not highlight this, caveat emptor I guess.

I have read about the foam options but they dont seem practical for hollow block construction. External is really expensive and would only be suited to my gable walls as the front is red brick.

Anyway appreciate the feedback, I think in my case I might just start off by internal dry lining of the gable walls and see if that helps. Also the attic only has 100mm of rockwool so I might upgrade that as well!!

I upgraded the heating to a new boiler and I also plan to put rad stats in all the rooms as I heard they help!

on the external insulation side,what width of board are they quoting you for your € 100 m. seems a lot