Insulating an old cottage

[Bluesky32]

Hi there, we have just bought an old blacksmiths cottage which is around 200 years old, its a brick built cottage with a 1930s/40s extension on the back and a granary which we are incorporating into the main house. at the moment we are stripping back the layers of new plaster/cement and other things that were on the walls so we can basically start again. Building regs have been out and said that we need to insulate all the external walls internally with a 25mm gap, 75mm kingspan (or similar) and then plasterboard and plaster to meet their regulations. My only concern is the external walls are all damp and our damp and timber surveyor recommended repointing externally with lime (a lot of it has been redone in cement) and plastering in lime internally to help with the damp, he has also recommended that we don't have a damp course which building regs were suprised about. But my question is if we have to meet building regs (who don't seem to consider the age of a building and building materials that were used) how do I prevent the damp leeching through the insulation and plasterboard and causing problems again. Can I just add that the house has never had any heating, had leaky guttering and has been empty for about 4 years so our surveyor has indicated that alot of the damp is condensation and the fact its not been lived in. I hope this all makes sense.

 

[AMc]

It does make sense

First you need to familiarise yourself with Parl L1B of the regulations and which version you need to meet (probably the latest one unless you have an earlier building control approval).
http://www.planningportal.gov.uk/buildingregulations/approveddocuments/partl/approved
You are obliged to insulate if you're renewing the wall coverings & aren't prevented by Lisiting but you are not obliged to meet the full compliance figures if it isn't "reasonable, feasible or economic".
What has been suggested is dry lining the wall which we did, but we had no evidence of damp problems. Notionally the kingspan should form an impermeable layer that prevents moisture moving into the house from the wall but unless the wall is also ventilated it could still build up and cause problems at the junctions or with the exterior.

You do need to consider the breathability of the insulation if you have a damp problem now and aren't going to be able to assess if it's going to be a long term problem. Breathable a.k.a. vapour permeable insulation is likely to be more expensive and less space efficient - using hemp board, sheeps or mineral wool and lime plastering. You'll need to do a bit of homework on the options and present your case to building control if the modern methods aren't appropriate in your house.

Good luck and keep posting!

 

[Keithj]

There is no such thing as a silly question - only silly answers!

The problem with the Building Regulations is that they were established primarily for new builds, where they make sense and can be applied. Trying to enforce them on far older buildings can be a futile exercise. We were "ordered" to fit large amounts of Celotex in our (Tudor) roof when we had some excessively heavy concrete tiles replaced with more suitable pantiles (we elected not to go back to thatch). It was only when the roofers came to do to the job and asked "where exactly are we supposed to put it?" that Building Regs realised there was nowhere for it to go and agreed (with no further debate) that it needn't be installed.

The presumption seems to be that you will comply with the regulations, unless there is good reason not to. If you have a listed property, you have some strong allies in the Conservation Officer, English Heritage, etc who can advise you. Otherwise, you need an "expert" to stand alongside you as you talk to the Building Regs people to identify what makes sense.

Unfortunately, in this green and PC world, cost is not a relevant consideration. Thus, while good technical advice may not be free, it can work out cheaper in the long run. Certainly, do not allow anyone to fit a "damp proof course" in a wall that did not have one. There are countless warnings about that, and we saw the futility of one that had been "installed" here when the rotten sole plates were removed. It didn't do what it was expected to do, it caused more damage than good, and looked pathetic when it was removed.

Building Control officers will normally respond to good logical advice. Putting waterproof materials into walls that were designed to breathe is often not a good idea, and they will see that.

 

[Bluesky32]

Thank you both for the advice. It's so confusing knowing what to do. We visited the Home renovation show earlier this year as we thought we would be able to get some advice and we came away even more confused!

 

[Flyfisher]

Lots of good points above. It is confusing because what may be good advice for a new property might be very bad practice for old houses, which are usually built according to quite different principles. So it's not really that any particular materials or methods are intrinsically bad, it's their inappropriate application that can do so much harm.

I'd certainly agree that "there are no silly questions" (and I've asked plenty of them!!) - the only silly thing is not to ask them! Seems to me that the house in question has found a sympathetic owner keen to do the right thing after a significant period of neglect. I'm sure it'll repay such thoughtful attention.

 

[middi]

I agree with the fact that some " modern " builders are not adept at using contemporary construction materials in order to benefit old buildings. The principles of their construction and materials used are not understood.

The perfect example has been highlighted in Keithj example regarding the use of DPC in a wall sole plate. There is nothing wrong in using a dpc under the wall plate of an old building, stupidity kicks into play only if the installer of the DPC fails to evaluate the fact that it totally useless to install this DPC if water can gain entry within the wall that is built above it.

( as Einstein quoted when asked what was the difference between stupidity and genius, he replied " there is a limit to genius"

Middi