Spinny

Utility room below has boiler, cylinder, washer, dryer, sink in it and wall extractor fan. Not had condensation internally before except on a single glazed window and in the old 1980's single skin kitchen extension. Not sure how much impact a rear and half side single storey insulated extension will have. The architect did say put insulation onto top section of the walls where they continue up to the outside, but not feasible (or considered) when the steel was put in. Thousands of openings must be made like this in the UK every week.

Steels were put at that level across the opening because to put the lintels higher in the wall would have meant disrupting the upstairs room and floor above and the existing ceiling joists. So the steels will reduce the ceiling level in that one room from 2.63m down to about 2.48m. I guess the builders put the cavity tray in as that was all that was feasible. To insulate the cavity area you suggest would mean cutting out the DPM cavity tray between the steels, and would still be very tricky given the variable block sizes and cavity width. Or else drilling holes in the wall upstairs to pump in XPS beads or something. Not sure I see it as worthwhile given the air itself has insulation value, and it doesn't stop the outer blockwork penetrating the roof. I am thinking I could try to do something under the DPM between the top flanges of the steel. (Anyone know if ordinary DPM roll is a vapour barrier ?) For example put some 25mm PIR directly under the DPM by taping onto the steel upper flanges with tescon vana air tight tape ? Or push 50mm rockwool in ?

Google's AI search response tells me: "...stone's R-value is around 0.108 to 0.114. " "While stone has some insulating properties, its walls are more about thermal mass than insulation. They absorb and release heat slowly, which can provide a thermal buffer, but they do not significantly reduce heat transfer through the wall. "

No the cavity wall above is a 1930's house wall, outer leaf stone blockwork, inner leaf brickwork, variable size air cavity of around 50mm due to variable block depths. See sketch.

Well yes in that they are below the level of the warm roof. However as the beams support the two leafs of the original house wall, the outer beam is supporting the outer leaf which as it runs up to the main house roof above the single storey side extension is therefore exposed to the outside air. The plasterboard for the ceiling will run directly below the beams but will have downlight penetrations and will not itself have insulation directly above. The ceiling void the steels sit in is therefore within the thermal envelope.

We have the ceiling height but it might make a tight fit with the top of the kitchen units. It will also deepen the depth of the rooflight 'wells' - something that hadn't occurred to me before the build and for a warm roof they get quite deep. Would indeed be nice if someone can comment on actual experience of using acoustic strip. I have one roll in my hands, seems quite sticky, and seems quite stiff to squeezing, so presumably doesn't give you a bouncy ceiling. We are going to have some ceiling speakers though, not sure of any implications there.

Acoustic strip is just self adhesive straight onto the existing joists though - no layout time trying to avoid all the lighting positions - no cutting time - less reduction in ceiling height.

The Builders Prj Manager took great care to ensure the joists could be notched over the steels to avoid the steels being proud of the joists. Strange to then completely ignore the hanger issue. (I suppose they are there because of the rooflights. I guess he had never done a build with rooflights before. (He was a former chef))

How about if I use acoustic isolation strip across the underside of all the joists and then cut it out where the hangers are ? (Might give me some slight sound benefit at the same time.) https://www.insulationuk.co.uk/products/50mm-tekfon-acoustic-isolation-strip-50mm-x-10m?currency=GBP&gad_campaignid=17325772288&gad_source=1&gbraid=0AAAAAoNNCLS46l0Skr_o4MTjiC7gA41RT&gclid=EAIaIQobChMIg-Gws-TsjQMVJJdQBh0YBiM8EAQYCCABEgIoRvD_BwE&utm_campaign=&utm_medium=cpc&utm_source=google&variant=54935887774075

Just wondering if there is some rough calculation that can be done. The outside leaf steel is bolted to the inside one in 3 or 4 locations so given it is a good conductor it represents a single thermal element which will reach a single common temperature throughout. Estimating the surface area of a 152mm by 102mm I-beam would give roughly 300L+400L = 700L where L is the length, so for 2 steels it is 1400L, but only 100L of that surface area is in contact with blockwork some 300mm away from the outside air. So if the inside temperature is 20C and the temperature of the blockwork is 0C, then the steel is 13/14 exposed to 20C and 1/14 exposed to 0C. So what is the temperature of the steel - maybe 18C ? So there is no reason to worry about an internal cold spot, although it is a source of thermal loss ? Am I talking horse manure ? Probably.

Question is, does putting insulation around the steel actually do any good, or does it make it worse ? If the steel is in the ceiling void then the ceiling void is also likely to be semi-warm given holes in the plasterboard for downlights, and/or ordinary plasterboard. If you insulate all around the steel (except the part in contact with the blocks above) then arguably you are stopping the steel warming from the surrounding air in the ceiling void. All you may do is create a nice cold steel insulated conductor down to the bottom face against the ceiling plasterboard ?

Is this to put in a new connection and stop cock & water meter under the pavement outside the property only, or presumably it may include trenching a new water pipe into the new house too ? You can put your own water pipe in between the house and the stop cock position in the pavement (at least around here you can - inspector has to pass it) - cost me £1k for 20m for that bit. I think some utility guys do bits of private work at weekends if you ask around.

Anyone ? I am interested in this one too as I have a similar situation where the outer wall of the original house was knocked through and then a pair of steels used to support the house wall above the opening. I too have a warm roof in the adjacent single storey side extension and this sits at a level just above the position of the steels. Must be a very common scenario. Because it is supporting the original house outside wall above which is 1930's that cavity wall above has no insulation, just a 50mm ish cavity. And there is a cavity tray formed using DPM over the steel. So in theory - outside leaf of original house gets cold - this conducts down the wall beyond the 150mm PIR warm roof, then hits the steel making it colder, then through the steel to the plasterboard underneath. Total distance 150mm (PIR thickness) + 175mm (joist depth under) = 325mm stone blockwork, then steel 152mm, then plasterboard/plaster 15mm - total distance to room around 500mm. In theory the steel is in the warm zone and above the ceiling, but it has a semi cold outer block resting on it ?

Have heard of counter battening but was never specified or part of our plan. We wanted the ceiling height to match the main house. We don't have any floor above, it is a single storey extension. Seems like quite significant extra work, cost, and time. Is there another way ? bash them up as tight as possible with a hammer ? and/or score out a bit of plasterboard behind them ? some judicious use of a multitool ? See photos

Will need to board the ceiling in the new extension soon. Some ceiling joists sit in joist hangars which therefore protrude down below the general level of the bottom of the ceiling joists. Also one or two joists not perfectly level in places with the rest of the timbers. When it is boarded is this likely to be a problem ? What can I do about it ?

The carpet looks damp ? If so you could pull the corner of the carpet up to look underneath. Difficult to see from your photo - does the rad pipe go into the wall ? Radiator is presumably under the window then. Is the rendered wall just a garden wall / boundary wall outside ?

Wow Dave. Maybe take some clear photographs of what is there now, with a tape measure to show the degree of overhang already, and do you have your instruction not to enter your garden evidenced in any way e.g. A witness, or contemporaneous and dated handwritten notes, or a written letter to the neighbour.

It is a single ply membrane adhered to 150mm PIR with a roof felt under onto a plywood deck. Specified by the architect who seemed surprised when I said it can be like a drum in heavy rain. Sound people told me the plaster board ceiling will not be much help once I puncture it with downlights and speakers.

Depends where you plan to put the acoustic insulation. In this case it is the other way round because I am trying to muffle rain noise from a warm roof, and I wanted to keep the acoustic insulation above the downlights.

If being pumped in then be aware the first stuff out of the pipe can be very very watery and in an ideal world you would dump it outside the area. Don't get it on your hands or skin, do wash it off absolutely immediately, I can testify it burns. One of our young labourers turned up in shorts, had to run around with buckets of water to wash it off his leg. Good luck. Don't worry too much about the pipe, ours got abused but survived.

So did I as the plumber didn't bother and they were long. Missed a couple and can see the tips in the surface of the slab now.

How will they pour the concrete in ? pumped through a pipe ? How will they move across the slab area ? Walk over it ? Using boards ? Pic of my 'power float'

I have no idea. I just know that once the boundary features like a wall and fence above are all removed there will be no way to know where it was. The PWA will create a huge dispute by including undimensioned drawings purporting to show the width of an extension up to a boundary line which has been destroyed. The issue is that I have a side access passage along the outside of my property, purposely designed to be just wide enough to take stuff through (wheel barrows, wheelybins, lawnmowers, bicycles, a small minidigger, a wheelchair etc). So should the neighbour's build be even an inch or two onto my land it will create real access restrictions on my property. The owner has taken the adversarial and antagonistic route throughout, never once choosing to tackle any aspect by just talking to their neighbour. And there is no justifiable reason for them not to just be reasonable. The boundary isn't parallel to their outer wall, yet they plan to build angular rooms just so they can follow the boundary and don't loose a few square inches. Their outer wall seems to be 350mm wide when if they were so desperate for inches it could easily be 300mm wide and parallel. It is as though they are more concerned with intimidating us than the value of their own extension.

I am considering a survey but have been told it will be legally worthless unless carried out by a RICS surveyor ? I get told contradictory things at different times and by different PWS's. Whole process seems completely broken and seems designed to create disputes and not avoid them. Obviously with no definition of where the neighbour is going to build they could build anywhere they like and any disagreement about where they build is completely unresolvable. Once the land is dug up there will be no features or anything to go by. Even the most simple of questions such as what ''capping'' are you using is rejected as' you have no right to know' and 'we are not telling anyone'. Whole thing appears to be a mechanism for bullying your neighbour and stealing any land you fancy and no-one can stop you.

Thanks I am being offered only 6 and photocopied sections out of planning drawings/a cross-section which are therefore unscalable and have no marked dimensions for anything on them. I am being told that is acceptable and the PWS and the PWA do not define where the build occurs ! Whole thing becoming insane.