Council regulation over the top?

[acurachris]

Hi

I am doing an extension and had a trial hole dug for the foundations which was to 1.4m (deep due to trying to find good ground - point 1 below). The water table was oily/contaminated and ground is obviously made up ground.

My council building inspector came out and inspected the hole and insisted that I needed a methane DPM lapped over the cavity (point 2 below). We had the ground piled and will install a block and beam floor (piling guy suggested it!). When I told the council guy we are using block and beam, he said that's fine, but you'll need two 1200g gas membranes (point 3 below).

Point 1
If we had gone to 900mm and told the inspector we were to pile the foundations, he wouldn't have seen the oily water table and probably would never even have thought about the methane barrier.

Point 2
Is there not a point to argue against the barrier based on the original house and small extension we knocked down not having one? If the house isn't protected, why should the extension be?

Point 3
Is having two barriers justifiable? Is that not major overkill on a site where the main house doesn't even have one.

Questions
How does he even know there is methane? Is there a way to test this and if so would that enable me to refuse the methane barrier if the test came back negative?

Do you think i have any right to appeal his request for two or any methane barriers?

Am i being over dramatic and should just get on with it?

Cheers, Chris

 

[Nakajo]

Would the test for methane be cheaper than installing the membrane?

 

[acurachris]

Would the test for methane be cheaper than installing the membrane?

That is an important consideration. I don't know if a test exists for this kind of thing.

 

[^woody^]

Do you live on an old tip?

 

[acurachris]

Do you live on an old tip?

Looking at the historical info it was likely an industrial site, but it's hard to pinpoint exactly. No indication it was a tip.

 

[tony1851]

You would probably be wasting your time arguing the point with the inspector.
There are tests for methane, but as pointed out, probably more expensive than installing a gas barrier.
Your point about the existing house not having a barrier is understandable, but the rule is that any extension should have a barrier
if gas is present - crazy I know.
Don't see the point of two barriers, though. If you incorporate below-floor vents discharging into a strip of gravel at the foot of the wall,
one barrier should surely be OK.

 

[lt8480]

The membrane is usually only half the "solution" the other half is then venting the gas away.

If you don't membrane, or membrane and don't vent, then you are making a problem worse, rather than "no change" which is what you are trying to argue, which is why its not accepted to omit on the grounds the existing house may not have one.

It's like an existing house having asbestos isn't grounds to continue to use asbestos in future works.

 

[acurachris]

It's like an existing house having asbestos isn't grounds to continue to use asbestos in future works.

That's not a good analogy at all! I'm not trying to use a "hazardous or banned" product. A better analogy would be "wearing a dust mask over one nostril whilst cutting a hazardous material".

The only reason I am posting back today is because the building inspector came to inspect the drains (different guy, normal one on holiday). I asked generally at what point he'd want to see the DPC, whether before or after the gas DPC/Membrane was installed and he was surprised i'd been told to put one in. He said (not my prompting, all him) "I don't see why he'd request a gas membrane when the existing house doesn't have one". In the next breath he said "he is a bit of a stickler though isn't he, and if he's asked for it, then that's what he'll be expecting".

I'm going to put it in, but it is completely pointless, when a standard membrane would do the same job the existing house is doing!

 

[lt8480]

That's not a good analogy at all! I'm not trying to use a "hazardous or banned" product. A better analogy would be "wearing a dust mask over one nostril whilst cutting a hazardous material".

I was pointing out my omitting you are potentially making the problem actually worse. Just because the existing house doesn't have a membrane continuing that approach doesn't results in a situation that it "no worse". And putting one in is certainly not completely pointless as it will restrict the problem to only the existing parts of the house.

Maybe a better analogy is it is like having damp in an existing house that's 100 years old. You however wouldn't use that logic to argue that DPCs, DPMs, cavities, roofing membranes etc. in the new parts are pointless. Obviously if you did that and then the extension gets damp there would be more damp overall and the problem would be worse... it is not no worse than in currently is.

I think people are often too laid back about gas simply thinking because you cannot see it isn't as much of a problem.

 

[mattylad]

Point 1
If we had gone to 900mm and told the inspector we were to pile the foundations, he wouldn't have seen the oily water table and probably would never even have thought about the methane barrier.

But he has seen it so he has to respond to what he has seen - he cannot just ignore it.

Point 2
Is there not a point to argue against the barrier based on the original house and small extension we knocked down not having one? If the house isn't protected, why should the extension be?

No, you cannot base new builds on how old builds were done, things change, regulations change, we learn from the past and learn to do things better.
Wiring regulations have changed since the house was wired, however you will have to wire the extension to the current regs and not the old ones just because that's what the house was wired to.

Point 3

Is having two barriers justifiable? Is that not major overkill on a site where the main house doesn't even have one.

Same response to point #2

Questions
How does he even know there is methane? Is there a way to test this and if so would that enable me to refuse the methane barrier if the test came back negative?

He may be familiar with the area and has encountered methane there before, he does not have to test just your land when for instance - he may have already have seen tests from a neighbor who did similar.

Do you think i have any right to appeal his request for two or any methane barriers?

Yes, you have the right to appeal - however IMO you'd need to show good reason for not doing so - perhaps the result of tests.

My question is, how would the cost of these tests (which may not show the presence of methane that may be present in the future)compare with the cost of complying?

 

[acurachris]

I think people are often too laid back about gas simply thinking because you cannot see it isn't as much of a problem.

Yes, fair point, although it's probably 10x more dangerous to walk around the polluted city centre than it is to sit in a house without a gas membrane!

I was pointing out my omitting you are potentially making the problem actually worse

Yes, okay, I see your point here.

No, you cannot base new builds on how old builds were done, things change, regulations change, we learn from the past and learn to do things better.

Yes I agree with this, although I think it's more pertinent for new builds rather than extensions.

He may be familiar with the area and has encountered methane there before

Possibly, although a house on the corner of my cup-de-sac (100 yrds away) had their extension done, and they haven't had a gas membrane. They had to do piling like my house due to poor ground though.

My question is, how would the cost of these tests (which may not show the presence of methane that may be present in the future)compare with the cost of complying?

Yep, I agree it's futile to go down the test route, I'll suck up the cost.

 

[mattylad]

Your extension IS a new build in the eyes of the planning dept.

 

[acurachris]

Your extension IS a new build in the eyes of the planning dept.

New development sites/houses.

 

[Leofric]

Is it a methane or a Radon barrier ?