Overview
I understand the property was formerly a 2 level single dwelling, the client wishes to convert this into 2 separate flats, with 1 flat per level, I understand that the client intends to convert the loft into a separate self contained flat at a later date but whilst the current conversion is being done he is going to treat for sound Insulation now whilst it is easy to do so. Access to all flats will be via a staircase located down one side of the property. The Building is of Brick and timber joist construction. Please see general arrangement sketch fig 1 below.
This is a very simplified representation of the layout, it is not to scale and should only be used for reference purposes.
Requirements
In a strict assessment of the situation the project falls with in the Conversion (Material change of Use) scope of Approved Document E of the Building Regs and as such should meet the standard criterion as detailed below.
Flat conversions Separating Floors
Separating Floor Between Flats Airborne Noise Reduction = 43dB Dn T,w + (Ctr) or greater
Separating Floor Between Flats Impact Noise Reduction = 64dB Ln T,w or less
Providing the separating floors between all the flats are treated in the same way, then we can limit the total number of tests required to the following:
- 2 Airborne Floor Tests to achieve 43dB Dn T,w + (Ctr) or more (between any 2 new levels created)
- 2 Impact Floor Tests to achieve 64dB Ln T,w or less (between any 2 new levels created)
Flat conversions Separating Walls
The only new Party walls being created separate each flat from the communal stairways, as such although they will need to be up to Party Wall spec (or as close as practically possible) they will not be tested however.
Please note: As the existing walls between this property and the properties either side, have always been Party Walls then there should be no need to test them, as there is no Material Change of Use, in any event they all appear to be more than capable of passing the current regulations.
I would advise that you check the above requirements with Building Control, as any change from the above will have affect the overall costs of testing. Unless we are told otherwise we will test as described above.
Current Status
The property is currently un-occupied above 1st floor level, work has already commenced with most of the partitioning completed on all levels, there are 8” x 2” Joists between Ground and 1st Floor, whilst the joists between 1st Floor and Loft are also 8” x 2” although these have been lowered slightly to create more floor to ceiling height. Most of the floors and ceilings are still intact, although in some places the plasterboard ceiling has been added after repositioning new joists. After running through several different options with the client, we eventually decided that the best way forward was to utilize independent ceilings in each room whilst above having a light weight floating floor to level off the uneven flooring. The client did express a desire to keep ornamental ceilings in the Ground Floor area however as I explained on site, this would end up more costly and be less likely to pass the eventual sound test. There is also a single storey extension being built at the back of the property, however this is will not be affected by Sound Insulation issues.
There are several other issues within this conversion that need addressing, I will cover all issues relating to Approved Document E within this report and have listed the main issues under the headings shown below.
- Party Floor between Ground Floor Flat and 1st Floor Flat.
- Party Floor between 1st and 2nd Floor.
- Internal Party walls.
- Internal stud work.
- Additional Flanking routes ie fireplaces and steel work.
- Bathroom fittings.
- Treatment of stairs.
- Loft Flat Treatment.
- Final fitting check list.
Please see below for each area under consideration and recommended treatment.
Party Floor between Ground Floor Flat and 1st Floor Flat
The current floor construction consists of 8” x 2” joists with Floor boards above and Lath and plaster ceiling below, although this is a good starting point, as I mentioned earlier we are going to install an independent ceiling below the existing ceiling. Please see below for step by step instructions.
Recommendations
From Above
- Install heating and electrics below floor surface as required.
- Re-lay floor boards as required, repair or replace where broken or missing.
- Seal all gaps with mastic or silicon.
- Render and plaster all external walls down to this ply surface and ensure no gaps in floor.
- Build up any new stud internal stud work on to this floor.
- Insulate studwork and then apply Plasterboard as detailed further down in the report.
- Apply skim coat plaster to all rooms right down to sub-floor level.
- Apply Isolation Tape to bottom edge of all rooms.
- Fit 28mm SoundFloor 28 Acoustic Floor to all rooms.
- DO NOT SCREW OR NAIL THIS FLOORING
- Stagger joints of boards.
- Glue joints and seal ALL GAPS with Sealant.
- Ensure new floor surface is completely water tight.
- Fold down isolation foam onto wooden floor and fit skirting on to it.
- Ensure skirting board sits onto Flanking tape and not directly onto flooring.
From below
- Repair existing Lath and Plaster ceiling where damaged.
- Add additional layer of 15mm SoundBloc Plasterboard to underside of existing ceiling.
- Fix wall plates around perimeter of room 10-20mm from overlaid ceiling.
- Suspend new Ceiling joists from wall plates ( Check size of joists with Structural engineer).
- Install 4” (100mm) insulation slab in new ceiling void.
- Stagger fix 2 Layers of 15mm SoundBloc Plasterboard to the underside of the M.F. Ceiling.
- Seal around edge of both layers of plasterboard to ensure no gaps.
- Ensure ceiling is completely watertight.
- Do not fit recessed ceiling lights in this ceiling.
Please see detail cross section fig 2 as below
Materials Required for above
- 1.28mm SoundFloor 28 2.4m x 0.6m x 28mm @ £ 15.48 per m2 + Vat
- Roll Flanking Tape (50m x 6mm x 75mm) @ £24.50 per roll + Vat
- Bottles Joint Adhesive (1ltr Bottles) @ £6.10 Each + Vat
- Tubes Acoustic Sealant (380ml Tubes) @ £4.05 Each + Vat
- Packs 100mm Insulation Slab @ £ 5.95 per m2 + Vat
- 1.15mm SoundBloc Plasterboard 2.4m x 1.2m @ £ 2.75 per m2 + Vat
All prices exclude Vat but include delivery to site.
I have assumed you will purchase timber and fixings locally
High Window Detail fig 3
If in creating this new ceiling the windows finish above the line of the new proposed ceiling, then you will need to use a slightly different detail, please see below:
This detail only needs to be used around the window, alternatively you can use right angle box section if you prefer not to have a sloping ceiling.
Party Floor between 1st and 2nd Floor
This is a slightly different situation although the treatment is going to be identical, as I mentioned earlier, the floor / ceiling here has been dropped slightly to create enough headroom in the loft flat, to support this floor, 2 large steel RSJ`s have been installed spanning the entire building. The new Floor joists then sit into this steel. Fig 4
Internal Party Walls
Under Approved Document E, you are required to insulate against Airborne noise in all walls that separate any part of a flat with another flat or communal area, in practice however we would only test between habitable rooms ie Bedroom to bedroom or living room to living room.
The client is only creating 1 type of Party Wall in this conversion, they will separate:
- a.The communal staircase from each flat
-
The communal staircase from each flat
These Party walls are all being created from scratch and as with most conversions of this type, space is restricted. In order to create more room, it will be necessary to reduce the thickness of the Party Walls. A normal stud Party Wall, would consist of 2 independent insulated studs, faced both sides with 2 layers of plasterboard.
In order to reduce this thickness but still retain a reasonable amount of noise reduction I propose that the following construction be used: fig 5
Due to severe restrictions on space, in the Loft Flat and 1st floor Bathroom, it may be necessary to reduce this thickness still further by taking away the Resilient Bars off one side of the wall around the bathrooms.
Please Note
Again I would advise that you check the above with Building Control prior to work commencing
Internal Stud Work
There is no requirement here except for the standard Rw 40 dB Wall that would normally consist of a 4” x 2” stud and a single layer of plasterboard with 50mm 10Kg/m3 Insulation, however I would suggest that you consider adding an additional layer of plasterboard both sides of the wall as well as using a higher density insulation such as SoundSlab as this will all provide extra Sound insulation from flanking noise traveling down the stud as they will all be in line with each other.
All internal stud work should be built onto the sub floor and plastered right down to sub-floor level, with the Acoustic floating floor only being added once all plastering has been completed.
Additional Flanking routes ie Steel Beam and fireplaces etc
In conversions such as these, there are always other routes that the sound will try to take during the test, these are called Flanking Routes, please see below for Flanking routes that have been identified:
- Open fire places on both levels
- Service pipes work running through Party Floor
- Steel work
-
- Electric Sockets in Separating walls
Open Fireplaces
With in each property, there is at least one open fire place, these will all need treating as shown below, both on 2nd and 3rd floor level to prevent sound traveling up the flue during the test:
Install a brick wall 4” thick using normal house bricks or high density blocks, you will however still have to leave the breather vents in the new brick wall to allow some ventilation of the Flues to prevent rotting of brick work. Please see below
Plan view of fireplace treatment fig 6
If you wish to leave the original cast iron fireplace in position then you will need to remove it first then brick up the flue behind before refitting the fire place. Remember the new owners must know that these fireplaces can not be used. Alternatively you can completely remove the fireplace and Chimney Breast as long as you rebuild the floor construction and wall voids created.
Service pipe work runs
I understand that some services will be taken through the floor, please see treatment as shown in the plan view below.
Plan View fig 7
Please Note
These pipes should then just pass through small holes in the floor and ceiling, please avoid cutting large service voids through a floor construction as these allow lots of sound through.
If soil pipes pass horizontally under the new ceiling, these should also be boxed in to reduce sound breaking out of the area, I would again suggest boxing in with an independent timber frame and packing the pipe with insulation before double boarding around the frame work, please see cross section detail below. Fig 8
Steel Beams
There did not appear to be any steel beams supporting the ceiling construction other than those already mentioned in section 2, however if this is not the case then these steels should be packed with insulation, before ensuring the new ceiling level passes below these steels. I have sketched below (fig 9) a typical treatment that should be able to be used in this situation.
Horizontal Steel treatment Fig 9
Electric Sockets in Separating walls
Under Approved Document E guidelines you are advised not to put sockets in both sides of a Stud Party Wall, as sound will try to break through at these points.
Bathroom Fittings
When installing sinks and toilets or indeed shower trays into rooms where acoustic floors are being installed then the flooring is the last thing to be added, you must never fit toilets etc onto floating floors as the movement that will naturally occur may damage tiles or joints.
Instead you should create a plinth for each item, the thickness of the floating floor and fix it directly to the original floor surface, you can then place the flooring up against these plinths using the Isolation tape as a seal. Please see fig 10 below.
The client wants too install Tiles into the Bathrooms, whilst having laminate flooring through out other areas, in order to keep heights the same whilst still maintaining the necessary isolation, I suggest that the following construction be used in all bathrooms. Fig 11
The total height of this construction will be roughly the same as the rest of the floor area
The product used here is
4.5mm Regupol underlay 18mx 1m x 4.5mm @ £8.75 per m2 + Vat
Treatment of Stairs
There is a standard detail within Approved Document E. with regard to impact sound from stairways. Please see fig 12 below. They suggest adding impact isolation matting on the stair treads
As no part of the stairway is above another flat then you will not need to treat the underside of the stairs apart from a small section in the 1st Floor Bathroom, here I would suggest that you create a timber frame around the stirs to carry 2 layers of plasterboard, you can then fit insulation slab underneath the stairs steps.
The other advantage of putting Sound Reduction Mats on the stair treads and landing areas, is that it will equalize the difference in floor heights caused by the addition of the acoustic flooring in each flat
Reverberation Treatment
There is a small section within Approved Document E that recommends that you ensure that any potential echo within communal stair wells is reduced as much as possible, in your project I have looked at this and would suggest that providing you use a good thick carpet and underlay with the odd picture hung at intervals up the stairwell then no further treatment should be required. Choosing textured wall and ceiling finishes would further improve the situation.
Loft Flat Treatment
On the upper floor, the client is utilizing roof space to create another flat, you need to ensure that the floor treatments detail above, are followed carefully up here as well as there are certain areas where it will be difficult to treat ie where the window is recessed in the roof via a small dorma style effect. I would suggest that the sub-floor is taken right to the eaves of the flat before then installing dwarf stud walls to get the shape of the rooms, the floating floor can then finish up against these dwarf stud walls. Please see below fig 13
Finishing detail check list
I have produced the check list attached for your convenience to ensure that you cover all the major points normally missed during installation, some of the points may not apply to you but most will so please read and follow carefully, if there is a problem with the actual test we will need to know whether these things have been done correctly.
I trust the above is acceptable but if you have any questions regarding the above then please call me on the numbers above, I look forward to hearing from you in regard to supply of the materials suggested and I remain
Yours sincerely
Mark Page A.M.I.O.A. (Associate Member of the Institute Of Acoustics)