Wed, 14 Oct 2026 14:55:15 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76462#Comment_76462 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76462#Comment_76462 Tue, 02 Mar 2010 13:22:15 +0000 mikeinwestcork I'm hoping for some thoughts on party wall construction
I'm overseeing the build of a pair of semis one of which will become my home. The outside walls will be made of 365mm Durisol blocks rendered inside and out with hemp lime render. For the party wall my builder is suggesting a single 215mm high density concrete block on the flat with a thick hemp lime render on either side. I'm wondering would it be better to use the blocks on their edge to form a cavity with maybe some insulation in the middle?
My main concern is noise but obviously a bit of insulation is no harm for when they go away at Chritmas etc.

Putting aside issues about concrete and Durisol blocks has anyone any comments about the sound insulating properties of these proposed solutions or any better ideas that would be equivalent in price?
(I intend to post more about Durisol soon)
Thanks in advance,
Mike]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76475#Comment_76475 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76475#Comment_76475 Tue, 02 Mar 2010 14:28:27 +0000 marktime
I'd think you'd be looking at 250 - 300 kg/m2 per unit mass to get somewhere near 45 - 50dBA.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76482#Comment_76482 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76482#Comment_76482 Tue, 02 Mar 2010 15:28:47 +0000 tony
I can explain why if necessary]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76503#Comment_76503 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76503#Comment_76503 Tue, 02 Mar 2010 16:17:27 +0000 mikeinwestcork
The more I think about it the more I think that by standing the 215X100 mm block on its edge I'm covering 7.5% more area with the same number of blocks or more relevantly I can cover the same area with aprox 7.5% less blocks and labour. This would go some way to offset the cost of insulation and wall ties. By doing so I would have lowered the density of the wall but incorporated a cavity, this is where I'm not sure which is better.

But Tony are you saying you would do 2x 215 on the flat plus a cavity ie a wall that is 530mm wide? What would you use for the batts? Yes I'd really appreciate you explaining why.

Thanks,
Mike]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76505#Comment_76505 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76505#Comment_76505 Tue, 02 Mar 2010 16:27:23 +0000 Paul in Montreal http://www.nrc-cnrc.gc.ca/obj/irc/doc/pubs/ir/ir693/ir693.pdf and also http://www.mikeholmesfanforum.com/phpbb3/viewtopic.php?f=10&t=28997&p=200853#p200853 - "There are 4 elements to soundproofing. Decoupling, Absorption, Mass and Damping. Insulation does the absorption, and is the least contributive of the 4 elements. In a standard wall or ceiling, the National Research Council of Canada has a quoted opinion that insulation all by itself as a soundproofing measure is almost not worth doing. I believe this is light of the large expense associated with insulation. The key is 'all by itself.' When used in conjunction with a decoupled system (clips+channel, staggered or double studs) insulation provides a much better return on investment.

Hope these help.

Paul in Montreal]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76508#Comment_76508 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76508#Comment_76508 Tue, 02 Mar 2010 16:40:02 +0000 tony
the more mass you have between you and next door the better --- better sound deadening

wall ties carry noise across so omit them and two 215 walls most likely wont need wall ties if restrained by floor(s) roof, front and back (back inside wall not to bridge cavity either

The insulation is crucial to stop thermal bypass

The insulation will assist in deadening sound and help keep you thermally isolated from them next door

If it is gable wall I would stop mine below the ceiling insulation and let theirs go on up ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76509#Comment_76509 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76509#Comment_76509 Tue, 02 Mar 2010 16:49:09 +0000 davidfreeborough
Will any joists or beams be penetrating the wall? Will there be stairs against the wall? If so, you need to ensure they don't cause noise to be propagated from one side to the other.

David]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76515#Comment_76515 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76515#Comment_76515 Tue, 02 Mar 2010 17:09:03 +0000 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76517#Comment_76517 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76517#Comment_76517 Tue, 02 Mar 2010 17:27:51 +0000 Timber
I wouldn't bother using 2x 215 leaves with a 100 mm cavity. That is WAY overkill, however it all depends how concerned you are with noise.

I would build 2x 100 mm leaves of dense aggregate block with a 75 mm fully filled cavity (to prevent thermal bypass).

Please watch out for flanking. The durisol blocks may allow flanking sound via the inner leaf of the wall. I would get an acoustic consultant to check out the details to make sure they will work.

You could always go for timber framed wall! 2x leaves of 89 mm studwork with a 50 mm cavity. Fill the whole lot with insulation to prevent thermal bypass and then line with 1x 15 mm wall board and 1x 19 mm plank.


Penetrations of solid party walls can be a problem, but then they can also be a problem with cavity walls!

Timber]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76520#Comment_76520 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76520#Comment_76520 Tue, 02 Mar 2010 17:34:27 +0000 mikeinwestcork There are no stairs or joists going into the party wall and where possible I have designed store rooms and bathrooms to be against it keeping living rooms and bedrooms away. In the one bedroom that has a party wall there will probably be a fitted wardrobe (possibly both sides). However what I had not considered is that the cooker hoods will be back to back on this wall in the kitchen.

I'm checking with my builder to get the density and dimensions of the block he is intending to use. I should have clarified this before starting the post....

Mike]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76525#Comment_76525 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76525#Comment_76525 Tue, 02 Mar 2010 18:37:09 +0000 chuckey Frank]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76707#Comment_76707 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76707#Comment_76707 Wed, 03 Mar 2010 18:50:57 +0000 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76713#Comment_76713 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=76713#Comment_76713 Wed, 03 Mar 2010 20:17:50 +0000 sinnerboy https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77251#Comment_77251 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77251#Comment_77251 Mon, 08 Mar 2010 21:53:26 +0000 mikeinwestcork
Could anyone help me estimate the likely dB value of the cavity with insulation option so that I can compare?

I'm aware that the Durisol is not insulated as such having a u value of 0.82W/m2K but with addition of the render and the fact that the other side even if not heated won't be freezing I'm ready to go with the best noise insulation. I would imagine that using Durisol for the whole job rather than changing materials might yield some advantages when it comes to avoiding flanking as the concrete will be continuous between the outside and party walls.
Thanks in advance as usual
Mike]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77255#Comment_77255 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77255#Comment_77255 Mon, 08 Mar 2010 23:44:46 +0000 tony
Workmanship is crucial -- point and fill all perps.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77258#Comment_77258 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77258#Comment_77258 Tue, 09 Mar 2010 08:27:19 +0000 marktime
edit: ensure the sample wall wasn't cement mortar rendered because that would make a significant difference to unit mass.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77265#Comment_77265 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77265#Comment_77265 Tue, 09 Mar 2010 09:12:56 +0000 tony
It is difficult to upgrade the sound insulation of a party wall and the marginal cost of 140 over 100 is small

If it were mine I would go 200mm.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77290#Comment_77290 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77290#Comment_77290 Tue, 09 Mar 2010 14:15:45 +0000 marktime https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77295#Comment_77295 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77295#Comment_77295 Tue, 09 Mar 2010 15:01:39 +0000 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77314#Comment_77314 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77314#Comment_77314 Tue, 09 Mar 2010 19:07:19 +0000 marktime
I put great store by staying with one skillset throughout and if the builder is comfortable laying 250 blocks and a 250 block answers the acoustic demand, then that would be my preferred solution.

It really boils down to the 90% rule, the last 10% is going to cost a lot more than the previous 10% so it's a cost/performance balance ranged against all the other elements in the construction.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77351#Comment_77351 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77351#Comment_77351 Tue, 09 Mar 2010 23:56:52 +0000 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77429#Comment_77429 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77429#Comment_77429 Wed, 10 Mar 2010 20:36:29 +0000 Timber
I bet the durisol value is NOT in the correct format.

The format for a site test (and for compliance with Bregs) is DnT,w + Ctr.

I would suggest that the durisol figure is Rw. This is a lab test result.

On site the DnT,w is usually 5 - 10 dB worse than lab, PLUS the Rw figure doesn't take into consideration the negative Ctr correction. for that kind of wall i would estimate a negative correction of 3 dB (ish)

So the 63 dB Rw figure COULD end up being a 50 dB DnT,w + Ctr on site. That still pass Breg of 45 dB DnT,w + Ctr or more. Its ok in an ok kind of way.

The two leaves of 100 mm block with a 75 mm cavity and some mineral wool will give between 50 and 55 dB DnT,w + Ctr which is ok. If you get to 55 dB that is pritty good, but some timber frame walls can get up to 65 dB which is a HUGE improvement over Bregs.

2x 140 walls will give you up to 60 - 65 dB DnT,w +Ctr, but is a lot thicker than a timber frame wall reaching the same spec.

It all depends on your expectations!

Timber]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77444#Comment_77444 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77444#Comment_77444 Wed, 10 Mar 2010 22:13:29 +0000 Mike George Posted By: Timber
It all depends on your expectations!

Timber

.... and the frequency.

At most frequencies I believe the Mass law means that denser materials [such as concrete blocks] out perform less dense one [such as timber frame] Here's Rockwool's slant on it http://www.international.rockwool-marine.com/applications/sound+insulation/sound+and+noise+theory/sound+theory/acoustical+mass+law

I suspect the concrete boys will spin it the other way]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77445#Comment_77445 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77445#Comment_77445 Wed, 10 Mar 2010 22:14:11 +0000 Mike George http://www.international.rockwool-marine.com/applications/sound+insulation/sound+and+noise+theory/sound+theory/acoustical+mass+law]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77476#Comment_77476 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77476#Comment_77476 Thu, 11 Mar 2010 11:27:55 +0000 mikeinwestcork I should probably plough through the very interesting information from the rockwool link above before posting but since I started the post I want to get something back up as soon as I can. I found a link from the Durisol site to an acoustic test done by an independent tester on a block of flats using Durisol. I actually phoned the tester and talked to him because I just thought that in addition to the test results as someone testing all the time he probably has a good 'feel' for acoustic properties of various options. He told me that he was amazed at how well the Durisol worked and really hopes he gets to test more houses made of it in the future. I asked him directly what would I expect to get with a 2x100mm dense block cavity with 75mm rockwool and he guessed at about 55dB. Well above regs but well short of the 62dB that the Durisol got.

I have attached the sound test results. Interestingly they are only one dB down on the lab results but this is because of the addition of the plasterboard so the danger warning by Timber above is valid even though the figures are for genuine field test results and in the correct format.

As a result of this and coupled with the fact that I'm using Durisol for the outside walls I'm pretty sure that I'm going to go with the Durisol.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77695#Comment_77695 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77695#Comment_77695 Sat, 13 Mar 2010 23:01:21 +0000 LizM http://www.robustdetails.com/]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77697#Comment_77697 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77697#Comment_77697 Sun, 14 Mar 2010 00:12:40 +0000 mikeinwestcork The nearest I could find would be at http://www.robustdetails.com/Robust-Details-for-Part-E-separating-walls-or-floors-sound-insulation-and-testing-Robust-Details-Limited-65d22b1#frame-0 but there is no way to compare different thicknesses of the different options to see which is the better and non of the examples even mention rockwool in the cavity which was suggested as the way to go here. Unless I missed something but for sure there will be nothing on Durisol in there.
Mike]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77700#Comment_77700 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=77700#Comment_77700 Sun, 14 Mar 2010 00:17:45 +0000 tony
Often they consider one area in isolation when a holistic view is needed. long way to go as yet.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106439#Comment_106439 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106439#Comment_106439 Mon, 28 Mar 2011 10:16:33 +0100 dstart
We are trying to separate tow old houses (600 mm stone walls) by block up the interconnecting doorways on all floors). We are keen to achieve very high sounds insulation (~55-60dB) and would like to use dense block (sorry about greenness...)

Which would be best sound insulation

215mm dense concrete block (i.e.laid sideways), with dense render both sides
OR
2x 100mm dense concrete block with 50mm cavity plus rendering

Also not sure if we should fill the cavity with acoustic mineral wall or not

Can you help?

Thanks so much

Daniel]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106516#Comment_106516 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=5435&Focus=106516#Comment_106516 Tue, 29 Mar 2011 03:20:46 +0100 tony