Dear Tony,
First of all, thanks for your brilliant website, I spent over three hours reading through it on a Friday night/Saturday morning!
I’ve got several questions regarding how defects in my new house should be amended, so I hope this won't use up my quota. Our supposedly 'prestige' builders have made the ground level on our road/pavement too high, meaning that the airbricks in our building are either below, or at, ground level. This means a small strip (about a foot) in front of our house cannot be landscaped, and instead, the builders are planning to install an accodrain or linear drain. Likewise, at the side of our end-terraced house, the block paving that was against our wall, but on the adjacent house’s drive has been removed and replaced by a grating, which I am told will eventually have another acodrain under it. However, the grating on the adjacent house's drive clearly obstruct the air-bricks and dpc. Should this be the case? As I understand it, a grating should be one course below the dpc and not obstruct the airbricks. What should I look out for once the accodrain is installed at the front of our house?
Second, alongside our garage at the rear of our house, the block paving on our drive slopes upwards to the point at which it rises above the dpc by two courses (there are clear signs of damp). I have been told that yet another accodrain will be fitted here, but given the height of the paving, this will presumably remain above the dpc. Would this conform with Breg? Should I just insist on the whole drive being re-paved instead of settling for another gastly heel-trap for my wife to fall in to, (well, her shoe at least — she's not that thin) or for me to drop my car keys in to?
Finally, the rear of my garage wall joins on to the end of my garden, which rises above the bottom of the garage wall by at least eight courses. Again, there are signs of damp inside the garage, and I have been told that this is because the dpm is not functioning properly. Our builders have said that they are going to dig up our garden, apply a new dpm and replace the soil (mostly rubble actually!) From what I have been told, the dpm they have used sounds more like a brush-on application rather than a solid substance that I have read about elsewhere. Is this possible? Given that the dpm did not work in the first place, would I be better off just insisting that they lower the level of my garden to reduce the amount of earth resting on our garage wall?
Any guidance regarding any of these issues would be very much appreciated.
Regards,
Charlos
Linear drains, dpc and dpm
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84-1093879891
Using a linear drain up against the brickwork to accommodate high ground levels seems to be more acceptable to some BCOs than to others, and I'm struggling to determine whether there is a national consensus on what's acceptable and what's not, as the BCOs to whom I speak are giving me conflicting information.
When I first queried this practice, a BCO working for a neighbouring LA told me that he'd allow it in exceptional circumstances only, and that the top of the drain would never be allowed to be higher than the dpc, yet a BCO in Liverpool told me that he was happy enough with the practice if that's what the builder wanted to do. If there are any BCOs out there who'd like to add their two-penn'orth, I'd be glad to hear from them.
My understanding at the moment is that using a linear drain in this manner is just about acceptable as long as it doesn't bridge the dpc (ie - is not level with or higher than the dpc), However, blocking off an air-brick with a linear drain would not be acceptable, as I understand it.
On your second point, the paving should not bridge the dpc at all and the fact that your builder seems to view linear drains as a cure-all for correcting any drainage issue where good practice has been overlooked or side-stepped completely, is worrying.
Finally, the dpm on the rear garage wall. I'm not sure what form of dpm has been used, but a paint-on type is normally reliable, assuming it's been properly applied, but it may be that a vertical drainage composite would be a better solution in this situation, possibly "backed-up" with a tuminous or polymer-based tanking product for extra security.
As this is a new property, it will be checked over by the BCO and possibly the NHBC bod at some point, to ensure compliance with the Building Regs and to issue a habitation certificate. If you have any concerns, you should check with your local BCO for their ruling.
When I first queried this practice, a BCO working for a neighbouring LA told me that he'd allow it in exceptional circumstances only, and that the top of the drain would never be allowed to be higher than the dpc, yet a BCO in Liverpool told me that he was happy enough with the practice if that's what the builder wanted to do. If there are any BCOs out there who'd like to add their two-penn'orth, I'd be glad to hear from them.
My understanding at the moment is that using a linear drain in this manner is just about acceptable as long as it doesn't bridge the dpc (ie - is not level with or higher than the dpc), However, blocking off an air-brick with a linear drain would not be acceptable, as I understand it.
On your second point, the paving should not bridge the dpc at all and the fact that your builder seems to view linear drains as a cure-all for correcting any drainage issue where good practice has been overlooked or side-stepped completely, is worrying.
Finally, the dpm on the rear garage wall. I'm not sure what form of dpm has been used, but a paint-on type is normally reliable, assuming it's been properly applied, but it may be that a vertical drainage composite would be a better solution in this situation, possibly "backed-up" with a tuminous or polymer-based tanking product for extra security.
As this is a new property, it will be checked over by the BCO and possibly the NHBC bod at some point, to ensure compliance with the Building Regs and to issue a habitation certificate. If you have any concerns, you should check with your local BCO for their ruling.