I have just discovered this site & hope someone can help. I have re-read my mail & appreciate it is quite long, I would appreciate your patience.
I have just has an extension built to a 1965 house. Our existing floor is suspended timber with a void of approx three foot. The base on this void is concrete. The Building Inspector thinks the house is built on a raft.
I have been down under the floor a number of times in the eight years we have been here & it's always been dry.
When the electricians came in they said there was water under the floor. I went to look and found a relatively large area of water, puddling to nothing. It is at a point on my rear original wall adjacent to the new extension.
The best I can tell you is that it is 35 bucket fulls (builders buckets) of clean water. I removed the water and found the source lightly gurgling in at the concrete floor - rear wall junction. This location is at a point on my rear original wall adjacent to the new extension. This point has to be at least two feet down from ground level if not a little more. The water "replaced" itself slowly.
The building inspector was called and said it's nothing to do with the building work, it must always have happened and we just did not notice it. This indeed may well be the case as he has pointed out the evidence of water ingress in the past.
There is a gentle downward gradient towards the house from the back garden. This gradient continues past the house to the road about 20 meters away.
During construction, and I have digital photo's, remnants of two small land drains were found in the now extended building. The inspector saw them at the time, they were broken (crystallised I think he said), and not doing anything. I should point out these land drains seemed isolated and not connected to anything.
I asked him since that as there was existence of a drain in this specific area, should not the issue of drainage be made but he said no.
He advised me to wait approx nine months and to monitor the situation & if I still was unhappy to consult an independent surveyor. Please note I am not critising any one here. He said that there is no structural damage-taking place to my property. He is of the opinion that this is the natural water level and is coming up from below, not through my new extension, which has a solid suspended floor. The builder agrees with this. He also said that during digging it was noted that the area was generally wet at that the earth was green at certain levels which indicated wet land. Please note I am liberally quoting here.
I think it has reached a stable level and I think it did rise during the day after a “full day of rain� but it may be my imagination. I am now starting to monitor it seriously.
The width of my house is approx 6m, the extension almost matches this length & extends to a new depth of 3 meters.
We think we have eliminated mains water, by turning it off in the road but it still gurgled in. However if a “reservoir� of water had built up this may be a false test. I also do not think it is sewage.
I hope this does not sound a stupid question but is this a problem, does it need to be resolved ? Any further ideas for testing what the water actually is ? I have started reading about land drains on this site but I just do not know if this is relevant.
I hope I have not “gone on� too much & all help will be sincerely appreciated.
Drainage since extention built
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84-1093879891
I think you have to follow the advice of the BCO and your builder, who have had the advantage of observing the problem at first hand.
It's not sewage - believe me: you'd know if it was raw sewage! It's unlikely to be mains water as there'd be a more or less permanent level, not a rise and fall, which does rather suggest that it's groundwater.
It may be that the intercepted land drains are involved in some way, or it could be that the building work has interfered with the natural pre-existing regime, but it's impossible to be sure without extensive, and expensive, testing.
While living over a damp or wet sub-floor is less than ideal, it's not a major problem. You could install a sub-floor pump, but I'm not convinced there's anything to be gained. I would certainly monitor the situation over the next 12 months or so, keeping a record of weather/precipitation and water level to see if there is a correlation. This time next year, if there's any sign of oit getting worse, then call in a building surveyor, but for now, stop worrying, as there's almost nothing you can do about it.
One simple test would be to dig a trial hole out in the garden to see if you can find the water table level and cross-check the level with the level of the sub-floor. This will tell you whether it's a simple groundwater reservoir or whether there is a spring beneath your extension.
It's not sewage - believe me: you'd know if it was raw sewage! It's unlikely to be mains water as there'd be a more or less permanent level, not a rise and fall, which does rather suggest that it's groundwater.
It may be that the intercepted land drains are involved in some way, or it could be that the building work has interfered with the natural pre-existing regime, but it's impossible to be sure without extensive, and expensive, testing.
While living over a damp or wet sub-floor is less than ideal, it's not a major problem. You could install a sub-floor pump, but I'm not convinced there's anything to be gained. I would certainly monitor the situation over the next 12 months or so, keeping a record of weather/precipitation and water level to see if there is a correlation. This time next year, if there's any sign of oit getting worse, then call in a building surveyor, but for now, stop worrying, as there's almost nothing you can do about it.
One simple test would be to dig a trial hole out in the garden to see if you can find the water table level and cross-check the level with the level of the sub-floor. This will tell you whether it's a simple groundwater reservoir or whether there is a spring beneath your extension.
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danensis
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