Insulation PIR vs Wood Fibre

[BlindPete]

We got this for the harl coat.

https://www.womersleys.co.uk/shop/renders_and_plasters/lime-green-stipple.

It was a runny messy job, but gave a really good key.

We then got ready mixed sand and lime backing at 1 to 2 1/2 with hair from the same place.

That followed with fine stuff ready mixed. (Unsure of the ratio)

Our plasterer has done a great job specialising in lime plaster and restoration works. He wasn’t keen on the insulated lime stuff. He said it was very strange to work with.

It’s been on about 6 months. Still not painted it. It’s full of depth and texture. Looks great alongside exposed stoneworks too.

Womersleys were well priced and delivery was seamless.

 

[malcolm]

1 part lime to 2.5 parts sharp sand should be safe. The Celtic lime putty looks fine.

I've never bothered to harl coat (that's thrown on to the wall rather than trowelled). I wet the wall with a garden sprayer, let it dry unti it is thoroughly damp but there is no water on the surface, then use a small 8 inch trowel so I can press the lime in nicely. It only gives you a thin coat but you can bung the rest on top with a normal trowel.

 

[stamas01]

1 part lime to 2.5 parts sharp sand should be safe. The Celtic lime putty looks fine.

I've never bothered to harl coat (that's thrown on to the wall rather than trowelled). I wet the wall with a garden sprayer, let it dry unti it is thoroughly damp but there is no water on the surface, then use a small 8 inch trowel so I can press the lime in nicely. It only gives you a thin coat but you can bung the rest on top with a normal trowel.

You mean 1 part lime putty to 2.5 sand right?

 

[stamas01]

You mean 1 part lime putty to 2.5 sand right?

Sorry you already edited. My fault

 

[fernicarry]

What sort of final finish are you going for? Flat like the lath and plaster that used to be there? Bear in mind that some people on here will have gone for a more rustic look where they don't mind some undulations in the finish and others will have gone onto brick that is pretty flat to begin with.

Are you doing the external wall to the left as well? The window reveal is probably the biggest source of heat loss but difficult to do much with as you can't get much depth of insulation into the reveals. Are you going to relocate the pipe chase? Is it ground floor with a ventilated solum underneath?

Tbh I think I would be putting in stud work with the insulation inserted into that. Two reasons, much easier to get the finish flat but also I'd be quite uncomfortable plastering onto the hard if the wall is likely to get saturated by the weather. The gap between the stone and the laths in the original construction was there for a reason. I know that means its going to be ventilated behind your insulation but that's just the way buildings in our part of the world are intended to work.

I'd also try to get a breather membrane under the floorboards and tape that onto the wall insulation to give an airtight seal between floor and wall.

 

[stamas01]

What sort of final finish are you going for? Flat like the lath and plaster that used to be there? Bear in mind that some people on here will have gone for a more rustic look where they don't mind some undulations in the finish and others will have gone onto brick that is pretty flat to begin with.

Are you doing the external wall to the left as well? The window reveal is probably the biggest source of heat loss but difficult to do much with as you can't get much depth of insulation into the reveals. Are you going to relocate the pipe chase? Is it ground floor with a ventilated solum underneath?

Tbh I think I would be putting in stud work with the insulation inserted into that. Two reasons, much easier to get the finish flat but also I'd be quite uncomfortable plastering onto the hard if the wall is likely to get saturated by the weather. The gap between the stone and the laths in the original construction was there for a reason. I know that means its going to be ventilated behind your insulation but that's just the way buildings in our part of the world are intended to work.

I'd also try to get a breather membrane under the floorboards and tape that onto the wall insulation to give an airtight seal between floor and wall.

Thanks for the comment much appreciated. It is one of the upstares room. The external "wall" to the left is not really a wall but rather the roof. I am planning to put Rockwool there.

Once I have a good finish I will install the woodfibre insulation. On top of that I am looking to achieve a flat finish just like the lath and plaster used to be there.

 

[stamas01]

How much lime putty do you think I will need per square meter if I mix it 1:2.5 ratio?

 

[noj]

Depends how thick you want the plaster!

By my reckoning, every litre of putty plus 2.5 sand will actually give a little over 2.5mm of plaster per square meter (the putty fills the gaps between the sand grains).

 

[lizziecupcakes]

Here in the UK they don't enforce it with old buildings, my BC officer was more than happy with my plan for 60 - 80mm wood fibre on the ground floor. It depends who the officer is I guess but if they understand old buildings then they should realise that's as good as it gets.

Why is there a BC officer involved in your project anyway? A bit of insulation doesn't warrant a notice.

Hi @Lacan07 and everyone else, I am researching wood fibre boards right now. I have a 3 bed semi-detached Edwardian house that has no insulation (solid wall).

I think I will be going with wood fibre boards. I live in the Kingston Local Authority area. May I know which company you used and brand of wood fibre boards for your home?

Thank you.

 

[lizziecupcakes]

Hi @Lacan07,

I was about to post this question as a followup today but you were quicker. I just need a few more details before I start this.

So:
1. What is a standard base coat lime mixture? Could you also please link example products for each component? I believe it is 1 part lime putty and 2.5 part sharp sand?
For example is this lime putty good? Or am I better of with simply using a readily mixed Lime mortar like this?
2. Do I need to do a "Harl Coat" to give my stone masonry wall key? If so is "Harl Coat" just a base coat diluted to the extreme?

Here is an image of a wall I am planning to insulate with woodfibre.

View attachment 10668

Thanks

Hi @stamas01 - how did your wood fibre insulation go?

 

[Lacan07]

Hi @Lacan07 and everyone else, I am researching wood fibre boards right now. I have a 3 bed semi-detached Edwardian house that has no insulation (solid wall).

I think I will be going with wood fibre boards. I live in the Kingston Local Authority area. May I know which company you used and brand of wood fibre boards for your home?

Thank you.

Hi, there actually aren't that many brands to choose from although plenty of stockists! 'Steico' is the most well known, 'Pavatex' is another. Unfortunately these products usually arrive on a pallet regardless of how much you buy so it doesn't really matter where you buy it from, the carriage charges will be roughly the same. I live in Surrey so I have the 'Lime Centre' near me in Winchester which is quite handy as I often buy and collect 5 or 6 bags of plaster / mortar at a time for various smaller projects.

'Mike Wye' also seem to be very popular amongst the restoration crowd and having spoken to them previously they're very friendly and knowledgable.

Its recommended that you go for between 40 - 80mm thickness only. The reason for this is you're moving the condensation risk into the fabric of the building, and also you need to allow some heat to escape into the wall during the worst of winter to avoid freeze thaw of the bricks. Of course this won't give you the same insulation qualities as modern rigid foam board, but at the end of the day its your house and you can go as thick as you want!

 

[lizziecupcakes]

Thanks so much @Lacan07 - I'll give them a call and check my closest Steico stockists.

My house is about 1115 sq feet (104 sq metres) .
It is a 3 bed semi-detached Edwardian house - 1906 - each room is on average 3m x 4m.
I think I will only insulate the bedrooms and reception rooms.

Do you know roughly how much it would cost me to insulate the house? Or, maybe it's better to ask how much you paid for your house and number of rooms (only if you don't mind sharing?). I am just working out rough costs right now.

 

[lizziecupcakes]

I've also just called a STEICO stockist just now. He was very helpful and said the costs are:

STEICO 60mm thickness: 600 mm x 1350mm board - is 11.38 + VAT. It seems very expensive, but I am thinking about protecting the house for the longterm.

Lime Skimming mix: £20.75 per bag - for a 3m x 3m room it will need about 4 bags

Does this sound about right?

 

[Kearn]

Hi @Lacan07.

I think the building regulation states that I need to achieve 0.25 W/m2K in Scotland. I doubt that 100mm wood fibre will achieve it let alone the 80mm option. How serious should I take this building reg?

Old buildings are exempt if you would damage the historic nature of the building by chasing daft regs - can’t remember the specific section, but it apples to all historic buildings not just listed.

 

[Lacan07]

I've also just called a STEICO stockist just now. He was very helpful and said the costs are:

STEICO 60mm thickness: 600 mm x 1350mm board - is 11.38 + VAT. It seems very expensive, but I am thinking about protecting the house for the longterm.

Lime Skimming mix: £20.75 per bag - for a 3m x 3m room it will need about 4 bags

Does this sound about right?

I'm in the middle of my renovation and haven't even started downstairs so can't help you too much on pricing. If you contact someone like Mike Wye he will give you a proper quote based on your 1115 SQF. Here's an old quote I got a couple of years ago (can't remember who from) for my ground floor which just covers external walls:

For 33m2 you will require:

42no. 40mm Warmshell boards @ £9.91 each = £416.22 + vat
2no. boxes Ejot H3 075 fixings @ £31.84 each = £63.68 + vat
29no. 25kg bags Duro @ £11.90 each = £345.10 + vat
1no. roll white fibre mesh @ £49.00 + vat
24no. 25kg bags Solo @ £14.90 each = £357.60 + vat
Delivery of 2 ½ pallets = £173.00 + vat
TOTAL = £1404.30 + vat

The Duro is a base plaster because all my walls are back to brick.

 

[Zebra]

So:
1. What is a standard base coat lime mixture? Could you also please link example products for each component? I believe it is 1 part lime putty and 2.5 part sharp sand?
For example is this lime putty good? Or am I better of with simply using a readily mixed Lime mortar like this?
2. Do I need to do a "Harl Coat" to give my stone masonry wall key? If so is "Harl Coat" just a base coat diluted to the extreme?

Here is an image of a wall I am planning to insulate with woodfibre.
Thanks

For a base coat lime mixture I would go 3 parts plastering sand to 1 part lime putty by volume. I would use a mixture of soft and sharp sand a bit like malcolm suggested for bricklaying mortar, but you don't need the interlocking strength of sharp sand when it's just a coat of plaster, and it's much harder to use.
That putty is fine, yes. You could buy ready mixed, it's extra money for something that's largely sand, but mixing on site is also hard work so up to you. I did both, started off buying Old House Store's Coarse Stuff .....then switched to mixing on site using a paddle in an electric drill.
You shouldn't need to pre-coat with anything. Just wet the wall down so it's damp not running with water. The plaster should key in fine.