Hello,

i have just purchased a Victorian terrace house, built 1890. It's in need of some renovation, for starters we will be taking the entire ground level floor boars up to insulate between the joists and then lay a new tongue and groove wood floor. We will also lay a new floor upstairs.

We would also like to re-plaster the walls, this would include taking the plaster off the walls (it was plastered in the early 2000s with a non-breathable plaster) and applying a breathable lime plaster. We want to use Breathaplasta, a newish lime based plaster: https://www.celticsustainables.co.uk/adaptavate-breathaplasta/

We are planning to take the floors up and lay the insulation ourselves, and then have a flooring company lay the boards. And with the plaster we will take the plaster back to the walls and then have a contractor in to plaster.

My question is with regards to Building control, i have read that if you are taking up more than 25% of a floor or more than 25% of plaster off a wall, it must then be inline with building regulations. By insulating the floor we will achieve better than the thermal target, but my concern is with the plastering of the walls on to bare brick. We really don't want to build a stud wall.

Having never done this before, what is the best route to getting approval/ when should i contact building control, before i start? Would an independent inspector be able to approve the works? It would be good to have it approved/ certificated in case we want to sell the house in the future.


Any advice would be much appreciated.


Thanks,

Posted By: thebeaconWe want to use Breathaplasta, a newish lime based plaster

Seems to be over double the price of other lime plasters. Why that product specifically?

My question is with regards to Building control, i have read that if you are taking up more than 25% of a floor or more than 25% of plaster off a wall, it must then be inline with building regulations. By insulating the floor we will achieve better than the thermal target, but my concern is with the plastering of the walls on to bare brick. We really don't want to build a stud wall.

Unless you are in a conservation area, or a listed building, you will need to meet the insulation requirements of Part L for the walls, and hopefully improve on them. So either EWI or IWI. Others on here will be able to better advise. You will be able to use the council building control or an independent firm, but I don't think you're there yet.

Certainly part L1B must be adhered to, but if you read it carefully, section 3.1 (pg6) describes the definition of "renovation". One might argue, or plead ignorance, that you are replacing a surface finish, and so no need meet the criteria for a thermal element as described on page 22.

That said, I wouldn't consider going to all the trouble, and just living with cold brick walls. If you are concerned about breathability, perhaps a layer of wood fibre insulation, then your lime plaster. Got to make a big impact to what I'm guessing is a solid 9 inch wall?

You may not even then have to fully meet the regs, as the effect on the building structure of too much insulation could be argued, as an "historic" building.

Please do consider insulation, it would be such a missed opportunity, not to mention additional carbon into our blighted atmosphere. It's terraced so only 2 external walls (end terrace...3 ?)

Don't miss the opportunity to insulate the external walls. There is a chance you may have a cavity wall do you know for sure. Our previous house late Victorian semi did and a builder would not believe me until I had taken a brick out to show him. You need not be too concerned then about the internal wall being breathable so you could use thermal plaster board.

If you have a solid 225mm brick wall then 40mm Pavadentro will not meet the Regs. In fact neither does the maximum, 100mm, but it gets close enough that I have never had a BCO quibble. Taking the new SAP 'base case' U value for a solid 225mm wall as 1.7, and Pavadentro with a lambda value of 0.042W/mK, you get a little better than 0.34 W/m2K.

Ref the floor insulation, you want a VCL on the warm side. I would use Pro Clima Intello. (Other intelligent membranes probably exist).

I have used Pavadentro quite a lot, in case you want to whisper (or ask publicly, I don't mind) any Qs.

i used steico boards over the others - a lot cheaper though not tongue and groove (not convinced it makes a huge difference - you can just foam any gaps). I went with just sand and lime rather than bagged for cost reasons (and I have luxury of space to tip large amounts of sand) - both for the base coats and finish coats (finish coats with mesh). Can offer more advice if you want to go this route.

No need to paint walls first. If putting IWI on the external walls have you considered the ceiling/wall junctions. Ideally the insulation would run all the way up the walls through the ceiling. But that is more invasive and might need the joist nearest the wall being brought in a bit to allow for the IWI to fit (if the joists run parallel to the wall). But if you are doing the floors upstairs as well might be possible. I would use inorganic insulation in the floor not sheep's wool.

Thanks again for the continued feedback.

Posted By: Nick ParsonsTaking the new SAP 'base case' U value for a solid 225mm wall as 1.7

what’s the SAP Base case?

Thanks i might ask some more questions re pavadentro. Are there alternative products? just pricing it up and its pretty pricey. i have 60sm of wall to do.

Posted By: djh If you're not planning to do the work yourself, then I'd recommend letting your chosen lime plasterer specify the product to be used.

We won’t plaster ourselves, so will speak with a plasterer re what product to use. Have been trying to research a good lime plaster to use. I spoke with Mike Wye and they suggested a lime plaster that works with Pavadentro.

Posted By: jfbIf putting IWI on the external walls have you considered the ceiling/wall junctions. Ideally the insulation would run all the way up the walls through the ceiling. But that is more invasive and might need the joist nearest the wall being brought in a bit to allow for the IWI to fit (if the joists run parallel to the wall). But if you are doing the floors upstairs as well might be possible.

I haven’t considered this. Thanks for bringing it up. Would i be able to insulate to the ceiling and then under the floor boards in the room above to the topside of the downstair ceiling, without removing the ground floor ceiling?

Posted By: Nick ParsonsRef the floor insulation, you want a VCL on the warm side. I would use Pro Clima Intello. (Other intelligent membranes probably exist).

Posted By: jfb I would use inorganic insulation in the floor not sheep's wool.

We want to use a breathable and hygroscopic insulation. Sheep wool is both of these, but i am weary of using it. what suggestions do you have?

Floor wise, will go with

Solid wood t+g oak floor
Pro Clima Intello VLC
joists with insulation (breathable hygroscopic)
layer hanging over joists to sit insulation in (what should this be)
additional layer required under joists?


What should i hang over the joists to sit the insulation in? And does there need to be another airtightness layer under the joists?



Thanks again.

Hello again. SAP is the Government's Standard Assessment Procedure for the energy rating of buildings. For many years one of the built-in assumptions was that an un-insulated 225mm brick wall with plaster on the inside had a U value of 2.1W/m2K (the 'base case'). the latest revision of SAP incorporated the results of some in-situ U value testing which showed that some solid walls performed better than had previously been assumed, hence the 'base case' U value for a 2255mm solid brick wall is no 1.7W/m2K in SAP.

There are other makes of wood-fibre available. Steico and Gutex are both, I think, cheaper than the Pavatex range. The methods of manufacture are slightly different and I think Pavadentro has been shown to be rather better at moisture-buffering, though I cannot remember the source for that assertion.