Re finish bare brick walls

[Mscott]

I’ve just bought a 1903 detached house that needs some restoration, and I’ve got a few questions for those with more experience—so apologies in advance for the long post!

 

The house has cavity walls that have had blown-in insulation at some point the white fluffy stuff. I’ve stripped back all the old plaster on the inside of the exterior walls due to a previous damp issue around the chimney from old, poor repairs. I’ve now sorted these problems, but some brickwork is still drying out from years of moisture exposure.

 

I’m looking for the best way to re-skim these walls and possibly improve insulation while I’m at it. I understand how damp works in relation to condensation, but I want to make sure I take the right approach to avoid future issues.

 

Options I’m Considering:

 

Option 1 – No Additional Insulation:

• 2x1 battens for a service void

• Plasterboard and skim

 

Option 2 – Light Insulation Upgrade:

• 2x1 battens on the wall

• Space blanket insulation

• Additional battens on top for a service void (as recommended by YBS SuperQuilt)

• Plasterboard and skim

 

Option 3 – More Insulation:

• 3x2 stud wall set slightly off the external wall

• Flexi-batt insulation between studs

• Plasterboard and skim

 

My main concern is whether any of these options could create condensation issues on the internal brickwork. I’d really appreciate any advice or alternative suggestions from those who’ve tackled similar projects.

 

Thanks for reading, and I appreciate any insights!

[Mike]

If it's feasible, then external wall insulation is always the preferred option.

 

27 minutes ago, Mscott said:

My main concern is whether any of these options could create condensation issues on the internal brickwork

They could, but the chances are significantly lower if you have cavity wall insulation. However are you sure that you do have it? it was pretty rare in 1903.

 

If you actually have solid walls and they are rendered + painted + in good condition, then the risk goes down, but if you have porous brick / stone / render then the risk goes up. Exposure to rain also affects the risk of wetting & ability to dry.

 

If you're adding MVHR (mechanical ventilation with heat recovery) then the risk drops significantly, as that reduces the humidity of the air and so the condensation risk.

 

The best option is to ask advice from the the insulation manufacturer / vapour control layer (VCL) manufacturer, or to commission someone to undertake a WUFI analysis.

 

38 minutes ago, Mscott said:

Option 1 – No Additional Insulation:

• 2x1 battens for a service void

• Plasterboard and skim

Would work, though it would be a shame to miss the insulation opportunity. But add a parge coat to the brick for airtightness (and read up on the importance of airtightness in general - lots of thread here.)

 

40 minutes ago, Mscott said:

Option 2 – Light Insulation Upgrade:

• Space blanket insulation

No!

 

42 minutes ago, Mscott said:

Option 3 – More Insulation:

• 3x2 stud wall set slightly off the external wall

• Flexi-batt insulation between studs

• Plasterboard and skim

Preferable of the 3, but add a parge coat, keep the insulation fully in contact with the wall, and consider a service void. A 'smart' VCL may also be advised (especially if you ask a VCL manufacturer).

 

Alternatively you could do similar in metal stud, which (having done both) I prefer to timber. See my comments in this thread (the rest of the thread is relevant too):

 

 

[Mscott]

2 minutes ago, Mike said:

If it's feasible, then external wall insulation is always the preferred option.

 

They could, but the chances are significantly lower if you have cavity wall insulation. However are you sure that you do have it? it was pretty rare in 1903.

 

If you actually have solid walls and they are rendered + painted + in good condition, then the risk goes down, but if you have porous brick / stone / render then the risk goes up. Exposure to rain also affects the risk of wetting & ability to dry.

 

If you're adding MVHR (mechanical ventilation with heat recovery) then the risk drops significantly, as that reduces the humidity of the air and so the condensation risk.

 

The best option is to ask advice from the the insulation manufacturer / vapour control layer (VCL) manufacturer, or to commission someone to undertake a WUFI analysis.

 

Would work, though it would be a shame to miss the insulation opportunity. But add a parge coat to the brick for airtightness (and read up on the importance of airtightness in general - lots of thread here.)

 

No!

 

Preferable of the 3, but add a parge coat, keep the insulation fully in contact with the wall, and consider a service void. A 'smart' VCL may also be advised (especially if you ask a VCL manufacturer).

 

Alternatively you could do similar in metal stud, which (having done both) I prefer to timber. See my comments in this thread (the rest of the thread is relevant too):

 

 

Hi thanks for the detailed reply.

 

yes it’s 100% a cavity wall which has had cavity wall insulation added (removed a few walls due to extension and also changed the windows an can clearly see it’s insulated.

 

okay I will have a read over that post now. 
 

So a parge coat Is needed in every option? 

[Mike]

10 hours ago, Mscott said:

So a parge coat Is needed in every option? 

Yes, it's a necessary part of airtightness (there's more on that in that thread).