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Posted: Wed Aug 03, 2005 10:49 am
by KRIS
Bought an old house recently, its got a path down one gable end wall from front to back. This wall was rebuilt in blockwork (rest of house is sandstone) 10 years ago and pebbledashed. The path is 4ft wide and goes between the house and a 6ft retaining wall holding back soil, trees and bushes. A WC soil stack at ground level goes under this path, which is stone flags and concrete.
Problem 1:- on inspection of the gable wall from inside, some damp is getting through from floor to waist level at back of house, forming black damm patches on wall.
Problem 2:- On exposing some of the blockwork indoors, it seems that the DPC, which consists of rubber mat bonded into the blockwork, is above the floor level of the interior of the house.
Problem 3:- The path on the exterior side of this blockwork wall is high than the interior floor level.
Problem 4:- We want to move the WC upstairs to a point obove the downstairs WC and have a common soil stack which serves both WC's. This soil stack would also take bath and sink waste. This means that the current upstairs WC soil stack (on a different elevation) would be removed and capped off or blocked off.
Can we do the following:-
1. Excavate the path to lower the level of the path to a point lower than the interior floor level? Would this cure the internal damp problem?
2. Use a common soil stack serving 2 WC's on different floors?
3. If we can do 2 above, can be put any slight bends in the soil stack between ground and 1st floor to make it line up OK?
4. How do we cap off an existing soil stack connection following removal of vertical soil stack?
Posted: Wed Aug 03, 2005 1:33 pm
by danensis
1. If you have got damp three feet up a wall it is unlikely to be rising damp. Indeed there is a school of thought that says rising damp is a myth, and has only appeared since the appearance of the damp-proofing industry. No where else in the world seems to suffer from it - just think about Venice!
Most causes of so-called "rising damp" are either "falling damp" or condensation. Dampness coming down a wall is due to either a leaking roof, leaking gutters, or leaking pipes - internal or external. Condensation is due to lack of ventilation.
If the wall is rendered, it may be that an inappropriate cement-based render has been used. A render has to be either totally waterproof - difficult with a cement based render, as hairline cracks appear with thermal movement, or breathable, as with a lime-based render (that is a render based on lime, not a cement render with lime added). Older houses that are built with lime mortars should always be rendered with lime renders as these promote autogenous healing - hairline cracks that do appear allow carbon-dioxide to get into the render and reform the calcium carbonate substrate.
Clearly you should lower the path below the internal floor levels, especially if the floors are on wooden joists. Are there air bricks, are there enough, and are they all clear?
2. There is no reason why you cannot have a common soil stack serving WCs on different floors, this is a common arrangement. You may want to incorporate an access point near the base of the stack. This can be part of the lower WC branch connector.
3. Why not extend the branch pipes slightly rather than having a wiggle in the soil pipe?
4. It depends how convinced you are you will never need the old connection again. If very permanent, put a balloon in the bottom of the pipe and fill above it with concrete. For less permanent measures, wedge a piece of slate or tile in the top of the pipe and cement over it.
Posted: Wed Aug 03, 2005 2:12 pm
by KRIS
Thanx for reply
The render appears to be cement based, but not 100% certain of this.
The internal floors are solid (stone flagged or concrete). No air bricks are present in the blockwork gable wall.
Digging up the ouside path and lowering it by approx 300mm will set the path about 150mm lower than internal floors.
The soil stack from the downstirs WC comes out of the wall and goes straight down, there is no vent pipe for this.
Also, how deep is the buried horizontal section of soil pipe likely to be? I know that from the point where the soil stack enters the ground, there is at least 8 ft between this level and the level of the IC foul waste inlet. Distance is approx 25 meters from soil stack to IC. (drainage IC seems to be a combined system with foul water and some surface water piped into it, some surface water goes elsewhere from guttering but thats another matter, I'll find out later)
Can I connect to the top of the boss on the ground floor WC pipe, extend straight up, connect the upstairs WC to the pipe with an angled branch connection, if necessary, then extend to roof level for venting?
Another modification required will be to put an upstairs en-suite WC and shower/sink in a bedroom on the same gable wall about 4 metres horizontal distance from where the proposed soil stack extension will be. Will I require another vertical soil stack (and extend the existing soil pipe buried horizontal run until it meets the new stack?) or can I branch off the existing and have two 1st floor WC's and a ground floor WC on the same vertical pipe?
As you've probably gathered, I am DIY man who is looking for easiest/best solution but with limited practical experience of drainage matters. Theres probably a lot of work involved but ive gotta do it, if it means lots of digging and faffing around with pipes then so be it, I only want to do it once, though.
The soil stack to be capped off will be very permanent, do I cap it at ground level or lower?
Posted: Tue Aug 23, 2005 11:26 am
by Tony McC
Depth of rest bend on SVP - impossible to say, as it could be anywhere from 300mm to 2 metres deep, but on these older properties, they are usually around 600-1000mm deep.
The above-ground section of the SVP should be straight, with any accommodation being provided by the connecting pipework from WCs, bath/shower/sink outlets. You should be OK in connecting two WCS plus the other household grey water outlets to the one SVP.
Posted: Thu Aug 25, 2005 9:58 am
by KRIS
Thanks for the reply - any sensible answer helps a lot to me as i'm a rookie. And a big "well done" to the administrators and technical experts who 'run' this site. keep up the good work!!
Posted: Fri Aug 26, 2005 6:29 pm
by Tony McC
Why do so many people assume there's a team of admins and experts behind this site? It's just me, I'm afraid, in me back bedroom, one a single pc. Mrs Taz occasionally brings me a mug of tea, but that's about the only help I do get!
That's the power of t'internet - we can be whoever we want to be! 