Old House-dry lining versus insulated slabs?

eamon11

hello folks,

its a 1946 bungalow with mass concrete 300 mm external walls. Small house.
Any pros or cons with the two methods above?
Was thinking 62mm insulated slabbing or drylining and using 70mm insulation in cavity.
Walls fully stripped now and No dampness as far as I can see in house.
Maybe I should also mention that walls are very uneven.

Many thanks.

TopTec

Insulating the external walls on a place like this is a given. I can't give you the science but I have almost finished insulating with similar boards and also slightly thinner boards on the internal apex ceilings.

The rooms I have done so far are TOASTY. I'm very impressed the way the rooms retain their heat. I mounted them directly to the walls using metal mushrooms then had the boards skimmed.

Worth every penny in my view.

One questions... you mention a cavity. Where is this on a solid 300mm wall?

TT

eamon11

Toptec thanks for the reply,

but I have to admit I didnt really understand it. I think you are talking about external insulation which has nothing to do with my question.
As for a cavity question, if I went with drylining its the cavity created between the wall studs.

Cheers

GreeBo

eamon11 wrote: »

Toptec thanks for the reply,

but I have to admit I didnt really understand it. I think you are talking about external insulation which has nothing to do with my question.
As for a cavity question, if I went with drylining its the cavity created between the wall studs.

Cheers

Either way you will be probably creating a stud wall away from the solid wall, if they are very uneven its your best bet.

You are going to be wasting the thermal mass of the house and your rooms will not retain heat only the air will be heated.

External insulation is the way to go.

TopTec

Sorry Eamon for the confusion. To make it clear I used insulation slabs on the insides of all external walls of my single storey cottage. No point insulating any internal walls unless you have an attached garage or similar.

I used foil backed slabs and mounted them directly onto the surface of the walls using the metal mushrooms fittings.

I used thinner insulated boards on the reveals of the windows and around the velux windows which I fitted when I had the roofs replaced. The reason for this was the outer frames of the double and triple glazing units dictated the thickness of the insulation I used.

As for GreeBo's assertion that external insulation is best, I think it depends on each property. Some will benefit more from external than others. I did a fair amount of research and choose the internal route.

Some of it has be up 4 years now and has never caused me a problem.

Hope this helps.

TT

eamon11

thanks greebo,

external insulation is not an option which is why I didn't mention it. I will not go into the reasons why its not an option as they are irrelevant.
If I understand you correctly, in your opinion dry lining is better than using just insulated slabbing against the wall?

Toptec I appreciate the detail in your post. Much obliged. Can you tell me what thickness slabs you used on the walls? And is the house very old or walls uneven? I too have an apex ceiling to insulate. I agree with you also that everything is relative and the "best" solution is never the same for every house.

Cheers

BryanF

Toptec does your house have mass concrete walls?

BryanF

eamon11 wrote: »

thanks greebo,

external insulation is not an option which is why I didn't mention it. I will not go into the reasons why its not an option as they are irrelevant.
If I understand you correctly, in your opinion dry lining is better than using just insulated slabbing against the wall?

Toptec I appreciate the detail in your post. Much obliged. Can you tell me what thickness slabs you used on the walls? And is the house very old or walls uneven? I too have an apex ceiling to insulate. I agree with you also that everything is relative and the "best" solution is never the same for every house.

Cheers

No more than 50mm insulated plasterboard

TopTec

BryanF wrote: »

Toptec does your house have mass concrete walls?

My cottage is in 2 parts. The front part built around 1945 is 9" concrete blocks, some of them made on site. The rear, older part is pre 1834, made of local stone.

eamon11 wrote: »

Toptec Much obliged. Can you tell me what thickness slabs you used on the walls? And is the house very old or walls uneven? I too have an apex ceiling to insulate.
Cheers

eamon.

On the north facing walls of the old part I used 85mm as that room gets no sun at all. On the rest of the cottage, newer and old, I used 50mm slabs on the walls that are external ones and normal 12.5mm slabs on the rest.

On the apex roof of the old parts I used 35mm slabs and used these to do the window reveals especially around the stone openings. When the roof was replaced the timber used was 5" so I used 2" celotex between the rafters and then the 35mm slabs for the apex ceilings.

The newer part has flat ceilings but I have 12" earth wool in the loft so I didn't need insulation there and used normal 12.5mm slabs.

The walls in the newer part were flat but in the old part were typically uneven but over a wide area. Despite using slabs and skimming I was never going to be able to correct the walls that were out of true but just accepted what I ended up with and I have learnt to work around the problems that causes.

Hope this helps, As I said earlier the cottage is warm, even though I still have the main hallway and a bedroom to finish refurbing.

TT

eamon11

toptec,

many thanks for the post. Your bungalow sounds very much like mine. Old part with very thick walls and a new part with a flat roof.
Tell me why did you go for the insulated slabs over dry lining?

Thanks again,

Eamon

TopTec

Dry lining to me means mounting standard 12.5mm boards either directly onto walls, using mechanical fixings or dot and dabbing, or onto a metal or wooden frame using mechanical fixings.

It is clear from the evidence that single skinned buildings lose huge amounts of heat through those skins whether they be poured concrete, blocks, wood or bricks. Cavity insulation is not an option so either external or internal insulation is the only way to reduce the heat loss. There are some demonstration vids on Youtube that show the differences.

For me balancing the costs of outer or inner insulation, together with ease of fitting were the keys and the efficiency of one over the other is argued long and hard by people who favour one of them and to be honest didn't figure in my choice.

Hope that explains things.

TT

agusta

eamon11 wrote: »

toptec,

many thanks for the post. Your bungalow sounds very much like mine. Old part with very thick walls and a new part with a flat roof.
Tell me why did you go for the insulated slabs over dry lining?

Thanks again,

Eamon

You can bond 50 mm insulated slabs to your internal walls instead of anchor fixing.this will allow for the unevenness of the walls,alternatively you could plaster or use bonding to make your walls good and then anchor the 50 mm insulated onto the walls

eamon11

thank you all for the replies,

much appreciated.

Bryan and agusta, why in your opinion is 50 mm slab sufficient? This would mean 12 mm slab with 38mm insulation. Is it not a case of more is better?

Thanks in advance,

Eamon

BryanF

eamon11 wrote: »

thank you all for the replies,

much appreciated.

Bryan and agusta, why in your opinion is 50 mm slab sufficient? This would mean 12 mm slab with 38mm insulation. Is it not a case of more is better?

Thanks in advance,

Eamon

What will the temp of the existing wall surface be after you drylin/plaster board. Either system in a retro fit scenario will allow some moisture through to this cold surface. Studies have shown (search Joseph little, breaking the mould series) that where you are insulating internally it is best to not over do it.