TL data for concrete block walls? [UK spec]

Does anyone have TL data for the standard UK wall construction method of 2 leaves of 100mm (4 inch) concrete block with 50mm (2 inch) of insulation between the leaves. I'd also like to know what I would need to build to achieve the same figures in timber frame construction.

Please read the stickies for "before you post". In the interim, IR 586 and IR 761 should provide more than enough data to answer your questions. Good luck and congratulations on surviving the snow storms. Andre

Thanks, Andre. IR 586 gives data for walls that are slightly different to UK 'standard construction' which have 20mm more concrete, 15mm less cavity and use wall-ties. I was hoping there would be some data on the UK spec walls but IR 586 is probably close enough for an estimate.

antimaps wrote:

Thanks, Andre. IR 586 gives data for walls that are slightly different to UK 'standard construction' which have 20mm more concrete, 15mm less cavity and use wall-ties. I was hoping there would be some data on the UK spec walls but IR 586 is probably close enough for an estimate.

You are welcome. The effect of the differences in concrete and spacing can be calculated with a fair degree of accuracy. It would be cumbersome to do it though. Modifiying the TL graphs and then recalculatimg the STC. What are you loking for? In Europe, including the UK, the standard metric for classifying the overall sound reduction of partitions is Rw, not STC. You will probably find about zero data on STC for UK partitions because of this. Andre

The long and short of it is, I'm trying to find out what kind of isolation my proposed block walls will give so I can then try to work out how to build a comparable ceiling/roof from timber frame. I was thinking of using the 'double stud/double board wall' configuration for the ceiling. The top spec version in IR 761 starts to fall short of the concrete block performance below 500Hz. Green Glue haven't tested a double stud wall, but they estimate that a layer of Green Glue would improve the performance by about 6 dB in that area. This will bring the TL figures of each wall to within 4dB of the IR 586 figures. I would be mounting both rows of studs on the inner leaf of the concrete wall, so I'd have to allow for some flanking noise as well. The problem is, the IR 586 results may be quite different to what I would get using the standard (therefore, cheap) UK building methods. I don't think there will be a huge difference, but that's only an uneducated guess. I'm surprised that TL data for the UK standard wall construction method is not easily found.

antimaps wrote:

The long and short of it is, I'm trying to find out what kind of isolation my proposed block walls will give so I can then try to work out how to build a comparable ceiling/roof from timber frame.

Instead of twenty question, tell us what is the construction that you are trying to match? :D To match double leaf concrete isolation with lightweight construction is expensive. Rather than match the wall construction TL, what amount of TL do you need? TL is expensive.

antimaps wrote:

I'm surprised that TL data for the UK standard wall construction method is not easily found.

I did not write that TL data is not available. I wrote that STC data is not reaidly available becuase the metric in Europe is Rw. Andre

AVare wrote:

Instead of twenty question, tell us what is the construction that you are trying to match? :D

It is:

antimaps wrote:

2 leaves of 100mm (4 inch) concrete block with 50mm (2 inch) of insulation between the leaves.

I have a choice between 3.5N/mm2 and 7N/mm2 blocks for the same price so I figure stronger is better. Each leaf will be joined with metal wall ties every 900mm horizontally and 450mm vertically. The wall will sit on poured concrete foundations 600mm wide and 1m deep (unless I can get building control to agree to less). On the inside, there will be about 13mm of plaster (bonding + finish). Above the ceiling will be a standard, domestic flat roof construction: 75mm x 220mm roof joists on top of 75mm x 100mm wall plates sat on the outer concrete block leaf.

AVare wrote:

Rather than match the wall construction TL, what amount of TL do you need? TL is expensive.

The studio will be 30m from the neighbour's house but right on the boundary of their garden. I reckon the double stud ceiling construction I mentioned should be enough as long as her geese don't mind. Am I way off mark? If so, is there a cost effective way to improve the TL of the ceiling? Would another layer of drywall + Green Glue (3 layers each side) make a big difference?

is this a stand alone building? with a peaked roof? if so, then an inner isolation ceiling should work pretty well - find a way to add mass to the exterior roof structure a perhaps using GG there as well as in the inner isolation ceiling.

gullfo wrote:

is this a stand alone building? with a peaked roof? if so, then an inner isolation ceiling should work pretty well - find a way to add mass to the exterior roof structure a perhaps using GG there as well as in the inner isolation ceiling.

Thanks Glenn Yes. It's a stand-alone building. No. It's a flat roof. The roof (not the ceiling) will be pretty ineffective at isolation if I follow standard construction methods as there will be air leakage all around. I can't seal it because building regulations require ventilation of the roof space. I suppose that adding mass will make the roof less resonant, or resonate at a lower frequency.

AVare wrote:

antimaps wrote:

I'm surprised that TL data for the UK standard wall construction method is not easily found.

I did not write that TL data is not available. I wrote that STC data is not reaidly available becuase the metric in Europe is Rw.

Well, I can't find any TL, Rw or STC data easily. I guess I'll be phoning some manufacturers tomorrow.

I edited the thread title for accuracy. I was asking the wrong question.

Please indicate that you have edited your first post to include information that I asked for several posts down in the thread. Andre

maybe having a drawing/photos of the building in question would help us to provide better guidance?

AVare wrote:

Please indicate that you have edited your first post to include information that I asked for several posts down in the thread. Andre

As well as changing STC to TL in the title, I changed STC to TL in the first post, but the wall description was there from the start, Andre.

gullfo wrote:

maybe having a drawing/photos of the building in question would help us to provide better guidance?

It's not built yet. I'm in the 'conceptualisation' stage. The reason I gave a specific wall construction is because that will be the quickest and cheapest way to create good isolation. Bricks and bricklayers are cheap over here. Carpenters, on the other hand... I've got a bit more info now. I'll do a sketch of what I hope will work and post it in a while. Thanks for your patience, everyone.

any option to build a concrete ceiling then?

Theoretically, I guess I could build it out of anything. Pre-stressed concrete beams are expensive compared to timber. Pouring a slab would be cheap, but very difficult. It would also require me to employ an architect to get the plans approved. There are certain things we can build without too much red tape. As soon as it gets 'unusual' men with clipboards and calculators start appearing. It's something I will think about. Let me finish the sketch and I'll see how much further I need to go.

Here's a sketch of what I hope might work. Dimensions are converted/rounded to Imperial for the majority audience here. This is not a commercial studio open to clients. I'm a composer who sometimes needs to record vocals, guitars, strings, brass etc. One or two musicians at a time. It's unlikely that I'll be recording drums, but I may want to hold weekend band rehearsals in there so I want to avoid complaints from the neighbours. The building will be single storey, detached from the house by 30m. The nearest neighbour is also 30m away, but the studio will be next to their gardens so, again, I want to keep the noise in. By building with standard UK construction methods I can use cheap and easily sourced materials, I avoid the need for architects and special planning permissions which are costly and time consuming. It also keeps the insurance companies happy. I know from experience of my current studio, that the walls will provide sufficient isolation for my purposes. I need to achieve similar isolation from the ceiling Roof details are estimates based on standard UK construction methods. I can probably get some insulation in the roof space, but the key point is that it needs to be ventilated front and back through a pierced soffit so I don't expect much isolation help from the roof. I haven't found TL data for either the wall or ceiling construction but Andre pointed me to data for similar constructions and Green Glue gave me an educated guess as to what improvements would be gained in the ceiling construction. I'm hoping that the TL of ceiling construction shown will be fairly close to that of the wall construction. If I'm wrong, will an extra layer of gypsum board/Green Glue top and bottom make a big difference? More insulation? Or do I have to start thinking about a poured concrete slab roof? EDIT: Just realised the block density is wrong. It's 198kg/m2 of wall which means 1980kg/m3 or 124 lb/cubic foot... I think.

a couple of thoughts: the 2x4 will not be enough for the joists and you're coupling the ceilings via the walls (and presumably any beams needed if you were to proceed with the 2x4 - which you shouldn't). instead, build a outer ceiling on the outer wall and an inner ceiling on the inner wall. this way the inner room is mainly decoupled from the outer room. use nested joists to increase the inner ceiling height if needed. this example needs some work to consider any drainage from moisture build, soffits on roof ends, etc but it should give you idea on how to structure things.

Ah! I didn't check the load specs for the ceiling timber. Thanks for the reminder. So the isolation gain from removing the flanking path will outweigh the isolation loss from having only one ceiling leaf between the noise and the outer wall? In the UK, moisture in the roof space is dealt with using 'warm-roof' placement of insulation or vapour barriers. Apparently, drainage isn't a normal requirement for our climate but I'll check with my building inspector. Thanks again, Glenn

i'm pretty sure you'll see an increase in isolation since you'll have more air space between the ceiling mass layers and no coupling or flanking there.