Minimum height of insulation build up on concrete slab

[Dave Jones]

25 minutes ago, Iceverge said:

 

This is completely bonkers.

 

It's not as if it's ye olde wall Henry VIII boinked an fluttering milkmaid against. 

 

Someone needs to challenge this legally.  

 

nothing to lose by appealing the decision. You can still crack on in the meantime. Would make your build 10 times quicker/cheaper.

[Dave Jones]

12 hours ago, Chanmenie said:

So 2 layers to give 300mm at £30 a sheet is £60 plus the extra muck away won’t be much if any cheaper than 200mm PIR.

I used 2 layers of 100mm Celotex so 88 sheets £4500 

 

remember 100/200 mm of celtoex doesn't work brick so you will paying the brick layer for more of his time. 150/300 does.

[IanR]

36 minutes ago, seano said:

 What do you mean by compromises Ian?

 

For me, the visible fixings are a compromise, on a residential building, but would be less noticeable within a strong industrial/agricultural aesthetic. Acoustically, they are poor, for both blocking external noise coming into the building as well as rain noise. Difficult to incorporate roof lights. While they have OK airtightness across the continuous roof and there are solutions for continuity to walls that are clad with the same product, some careful detailing is required to the walls if you plan different wall construction.

 

You may wish to mitigate some of those compromises with internal ceiling/wall studwork, plasterboard and perhaps acoustic insulation, but this needs to be balanced with what additional weight the SE can accommodate through the portal frame. If the SE starts wanting any new structure to take the loads down to ground floor level via load bearing walls then you may as well build that structure to carry the thermal insulation that doesn't carry the compromises. The SE would also need to satisfy themselves that the existing slab was capable of taking the loads. Is there a ring beam, for instance, already incorporated into the existing slab and are the reinforcing steels of known size? If there are existing heavy (masonry) external walls to the barn/shed, that aren't showing any movement, then that should give the SE some confidence.

Edited February 22, 2023 by IanR

[Chanmenie]

10 hours ago, Nickfromwales said:

Can you share where you purchased for the OP, please?  And how long ago, of course, as the world's gone entirely tits-up over the last few years.  

Just checked my invoice

24/06/2022

88 sheets 100mm Celotex £3366 + VAT £573. so total £3939 

[Dave Jones]

1 minute ago, Chanmenie said:

Just checked my invoice

24/06/2022

88 sheets 100mm Celotex £3366 + VAT £573. so total £3939 

 

well over £50 a sheet now. Inflation!

[Chanmenie]

38 minutes ago, Dave Jones said:

 

remember 100/200 mm of celtoex doesn't work brick so you will paying the brick layer for more of his time. 150/300 does.

Why would floor insulation need to be brick coursable ?  Surely brick courses are irrelevant as the insulation goes inside the foundations at whatever height you put the hardcore to.

I laid my own foundation walls  and installed the hardcore and insulation no probs.

[Dave Jones]

4 minutes ago, Chanmenie said:

Why would floor insulation need to be brick coursable ?  Surely brick courses are irrelevant as the insulation goes inside the foundations at whatever height you put the hardcore to.

I laid my own foundation walls  and installed the hardcore and insulation no probs.

 

you want the inner and external courses to be exactly the same height for wall ties if nothing else!

[crispy_wafer]

10 minutes ago, Chanmenie said:

Just checked my invoice

24/06/2022

88 sheets 100mm Celotex £3366 + VAT £573. so total £3939 

 

Quick check @ Insulationhub.co.uk would be about the same

 

[Chanmenie]

7 minutes ago, Dave Jones said:

 

you want the inner and external courses to be exactly the same height for wall ties if nothing else!

yes of course but how does that relate to floor / insulation height, if its a ground bearing slab inside the foundation walls its independent of the foundation walls.

I can see the relevance if using block and beam but not for ground bearing.

[Dave Jones]

yes of course if you not using b and b.

[Marvin]

The devil is in the detail!!!

[Nickfromwales]

10 minutes ago, Marvin said:

The devil is in the detail!!!

Fabric first approach wins every single time, without exception.

You design once, you insulate once, you go mad on airtightness once, and then you reap those benefits every day until you cark it. Money in the bank, in an ever changing ( worrying ) world of energy dependency.

Why are our building regs standards still so utterly shite?!?

[Marvin]

In my humble opinion: For all those entering the world of improving there home:

 

Aim to go APE 

It worth considering all the AIM and APE elements before making decisions. That is Airtightness, Insulation, Mechanical Ventilation with Heat Recovery OR Heat pump Ventilation, and Air Source Heat Pump, Photovoltaics and Electric Vehicle.

 

Some of these will not work properly without the others, and some will complement others:

 

1. A MVHR will not work properly without Airtightness.
2. An Air Source Heat Pump will have to compensate for the lack of Airtightness and/or Insulation to the degree that the benefits become questionable, especially during winter, without them.
3. An ASHP uses electricity and Photovoltaics can supply a little during winter and a lot during summer when cooling can be a problem and an ASHP can supply cooling.
4. PV can supply a little to an Electric Vehicle during winter and plenty during summer if your vehicle is at home during sunny days.
5. Extending a property and only doing AIM works to the extension will be no good, you have to do all the property within the thermal envelope. 

 

And thinking of running costs:

a)     Airtightness and Insulation should have no running costs and last (Well, loft insulation lasts over 40 years, in our experience) with the exception of UPVC  units for windows and doors, but that being said it will last 30 years?

 

b)    Our MVHR unit servicing 100m2 floor sized home uses about 260kWh a year; far far less than would be used to heat incoming cold fresh air in winter, and we clean the filters twice a year.

 

c)     ASHPs are, in my opinion, still in their infancy but we are now in the second year of use here. We were very careful to follow best practice in the design and installation of our system, did a lot of bespoke tweaking, and we now have an upgraded 1970’s timber framed bungalow that uses less than 20kWh per year per m2 of floor for heating.

 

d)    PV would be a lot less attractive if there is no ASHP or EV (or battery backup) or diverter to the hot water immersion. In my humble opinion, if you have a suitable roof you should install as much a physically possible. Electricity production costs (cost per kWh) are difficult to evaluate because it depends how much is used and how much is supplied to the grid. We decided to go with the PV cost divided by 7 years, which for us works out at £1.60ish per day. Yesterday the PV produced 12kWh all of which we used. Remember, 5kW of PV panels will not produce 5kW because you would have to have:

                        i.         No shadowing of any of the panels during sunlight hours (like trees, buildings or chimneys.

                       ii.         All the solar panels face exactly the right angle in relation to the summer solstice midday sun for their                                           position on the planet. (Perfect angle facing south and perfect slope)

                      iii.         solar panels completely clean

                      iv.         the sun is completely unobscured

                       v.         the Inverter is 100% efficient

                      vi.         all the other losses due to cables, and equipment, and so on.

 

e)    Knowing the above PV limitations professional installers often add extra panels to make up for these losses. (Our inverter allows us to add roughly 28% more panels than its kW rating)

f)      PV panel installations will produce about one fifth of the power in the winter compared with what is produced in the height of summer.

 

g)    The electric vehicle and charging from the PV only really works together if you can have the vehicle plugged in during the day and supply over 3kW from your PV (or a large proportion of that). This is why we went for the biggest PV that would fit on the roof.  We then installed a system which only charges the when the PV is on and generating over 2kW in winter and 3kW in summer. (we have a 13amp charging system).

 

So, if finances cause you to have to consider only a few in my humble opinion AIM first and go APE later. (But prepare the property for the APE works as much as you can).

 

Best of Luck

 

Marvin

[Chanmenie]

2 hours ago, Dave Jones said:

 

well over £50 a sheet now. Inflation!

 

EIS have 100m sheets at £37 + VAT so not far off what i paid in June,  So you don't want to be paying anything over £50 a sheet

[Andehh]

For the sake of OP's question, the answer is 125mm PIR to get min for building regs (approx I think? ) I'd encourage going for 150mm.... But asking him to excavate down and go with passive house equiv is excessive. 

 

The return on investment for going 200mm PIR and excavating to make it fit would have a payback time beyond his lifetime!!! 

 

[Nickfromwales]

1 minute ago, Andehh said:

 

The return on investment for going 200mm PIR and excavating to make it fit would have a payback time beyond his lifetime!!! 

With todays energy prices ( and future ) I'd take that statement with a pinch of salt, sorry.

 

I often suggest sand blinding > 25mm sacrificial EPS > DPM > 100mm EPS > 100mm PIR if the depth is there without £££'s, but same can be achieved with 150mm of PIR. IIRC 140mm is B.B.Regs for a heated slab, but I haven't slept much this week. The maths are further impacted on whether it's being heated by oil / LPG vs a well matched heat pump  

[IanR]

33 minutes ago, Andehh said:

But asking him to excavate down and go with passive house equiv is excessive. 

 

Why is PassivHaus levels excessive? 150mm PIR doesn't even meet the proposed 2025 Building Regs.

 

With a 2,600 ft² footprint, I'd be concentrating my insulation on the floor and roof. 

[Iceverge]

@seano

 

 

 

 

 

 

 

 

 

 

That is 2 layers of OSB3 floating 

 

1 layer of this for the UFH (its about £30/m2)

 

110mm of the K103 Phenolic insualtion @ about £55/m2.  157mm.  Total £85/m2 not cheap. 

 

 

You could bin the UFH and use rads and save 25mm and just meet the 0.18W/m2/K limit with just 110mm K103 @ 132mm. 

 

 

 

 

 

 

 

 

 

[Iceverge]

For what its worth 225mm of EPS 70 would give you the same U value as above but would only cost £12.60/m2. 

 

 

 

Over 250m2 UFH and phenolic speciality boards would be £21,250. EPS would be £9500.

 

Bump it to 300mm for a U value of 0.12 and put some of the left over change towards digging out the old floor you'll still come out ahead. 

 

 

 

 

 

[HughF]

Bloody barn conversions….. as a welder, who’s spent a few too many weekends doing column repairs for people doing class Q conversions, my suggestion would be to always assume that you’ll need to dig out and replace the bottom 1000mm of each column.

 

I hate these darn barn conversions, always a compromise.

[seano]

1 hour ago, HughF said:

Bloody barn conversions….. as a welder, who’s spent a few too many weekends doing column repairs for people doing class Q conversions, my suggestion would be to always assume that you’ll need to dig out and replace the bottom 1000mm of each column.

 

I hate these darn barn conversions, always a compromise.

 

What's the reason for this Hugh?

 

[seano]

22 hours ago, Iceverge said:

@seano

 

 

 

 

 

 

 

 

 

 

That is 2 layers of OSB3 floating 

 

1 layer of this for the UFH (its about £30/m2)

 

110mm of the K103 Phenolic insualtion @ about £55/m2.  157mm.  Total £85/m2 not cheap. 

 

 

You could bin the UFH and use rads and save 25mm and just meet the 0.18W/m2/K limit with just 110mm K103 @ 132mm. 

 

 

 

 

 

 

 

 

 

 

That's a great tool you're using there.

 

[HughF]

4 minutes ago, seano said:

 

What's the reason for this Hugh?

 

Because in my experience the bottom 1000mm is always a rotten mess thats 90% rust.

 

My preferred repair method is to kango down into the ball, cut the steel off with plasma/oxy fuel, then splice in a flat plate bottomed repair section of a matching size UC. Resin studs down into the remains of the concrete ball and then grout under the plate.

 

Ideally, all the columns would be blasted (best) or needle gunned (acceptable) and primed before you even start work. Just to see what’s left after blasting.

Edited February 24, 2023 by HughF

[seano]

12 minutes ago, HughF said:

Because in my experience the bottom 1000mm is always a rotten mess thats 90% rust.

 

My preferred repair method is to kango down into the ball, cut the steel off with plasma/oxy fuel, then splice in a flat plate bottomed repair section of a matching size UC. Resin studs down into the remains of the concrete ball and then grout under the plate.

 

Ideally, all the columns would be blasted (best) or needle gunned (acceptable) and primed before you even start work. Just to see what’s left after blasting.

 

Got it.

This one is only 10 years old so fingers crossed is in better shape than most. The SE seems to think so anyway.

 

[IanR]

3 minutes ago, HughF said:

Because in my experience the bottom 1000mm is always a rotten mess thats 90% rust.

 

I'm in agreement with you and made the same point myself. But, you are being called in to repair corroded columns, so that's what you are seeing.

 

While I made the same point, I didn't have this issue with my own frame, but have seen it in others. I did "square up" a number of columns that were 2" - 4" out of plumb though. It needs to be checked, preferably before purchase, or needs to be budgeted for if it can't be checked. 

 

2 hours ago, HughF said:

I hate these darn barn conversions, always a compromise.

 

...but it can be the ticket to a residential property in a location that there is no other route to gaining permission. Such a shame that there is not a legislated route to a knock-down and rebuild development if there is no architectural/heritage/historic merit in the existing structure.