Digging through slab to replace pipework

[MissyB]

Hi All,
In one of our extensions we have 2 drain holes, was previously a carport/garage but previous owners enclosed it into part of the house. We are now getting some of its issues sorted and making sure in meets building regs but before we blocked the manholes and moved them outside we wanted to check the pipe which runs the length of the extension about 4.8mts. It occasionally (every 2-3 months) blocks up so I had one of those camera things down it and it looks like we are going to have to dig it all up as the first metre of pipe is displaced and kicks back causing the water to sit and not helping the paper move along the pipe.

So my questions relates to the foundations. Can anyone advise on tying in reo from the old to the new where we repour once having laid new pipe? What happens if we dig and find the slab has no reo? What happens if we find a double slab, base with reo top layer without? It's really just a gut feel but we know part of the extension was redone on insurance claim some 13yrs back due to a tree root in neighbours garden and knowing that building regs were not applied for at the time we are concerned that this could be an issue we have to deal with.

Any help on the foundations much appreciated.

Thanks
Belinda

 

[Joe Malone]

Have you investigated the possibility of simply getting the defective pipework lined by a specialist company? It could save you a lot of time and expense and may even be covered on your buildings insurance.

 

[rssteve]

whats reo?

 

[Joe Malone]

I'm guessing it's steel reinforcement?

 

[MissyB]

Hi,

Thanks for the replies. Regarding the repair, the company who did the survey of the drains does this but they said the liner only fixes sliped pipes or broken pipes, as ours falls backwards he said it would prob not remedy the issue. He is going to get someone else to look at the DVD of the drains but said it was not hopeful and felt excavating was the answer.

Yes reo is steel reinforcement, sorry, originally from Oz old habits die hard. If anyone can answer these questions would really appreciate it as we just want to know what the worst case could be, I am guessing if there was no steel reinforcement then we would have to redo the entire slab??

Thanks
Belinda

 

[Joe Malone]

Belinda, it's not that easy to understand the problem; I'm guessing that's why you haven't had much response.
Are you simply taking up a floor slab in the garage because if you are then I'm failing to see the issue with the foundations or the reinforcement?
We really need more details on the construction, particularly the type of foundations?

 

[MissyB]

Hi Joe,

Sorry for any confusion, partly this is because we are working on assumptions as when we bought the property there were no records of this extension. The house is a 60's bungalow and the extension in question we believe was originally the carport or garage however are not entirely sure.

It is a flat roof construction and we believe may have been built in the 70's. We do know in 1995 it was subject to an insurance claim from one of the previous owners due to tree root damage from a neighbours property however at the time no building regs were obtained.

Because of this we really do not know what type of slab it has or how thick the slab is. My husband feels it may have had a second slab poured on the orginal to bring the finished floor level up to that of the existing bungalow but we can not be certain. I guess with 2 manholes in this extension we could remove the bricks surrounding to at least see the depth of the slab.

I know this is a load of assumptions but if the orginal slab was done with the house as a carport/garage then are we right to assume that it would have steel reinforcement? However if a second slab was poured over this to bring the floor level up does this need to have steel reinforcement? We have never really dealt with UK foundation issues until now so only know what we would expect based on Australian regs.

Any questions please ask, hope this makes sense.

Thanks
Belinda

 

[Joe Malone]

Belinda, have you considered digging a trial pit at the side of the garage to investigate what foundations you have; it's a relatively simple task and could answer a lot of your questions.
My guess is that the garage was laid on a trench foundation and has a separate floor slab. This would make things easier for you. The garage floor may or may not have reinforcement, my guess again is that it won't but you you can either get it checked using a covermeter or a metal detector or simply start and dig it up.

 

[Joe Malone]

Pictures might help if you can post some!

Also, I don't know whether this is possible but have you considered an alternate route for the new drainage, i.e, is it possible to disconnect before the garage and lay the new drainage around the garage?

 

[MissyB]

Hi Joe,

There no way we can divert the pipe elsewhere, it's the soil pipe and the bathroom is internal now because the extension closed it in. To go in the opposite direction would mean finding if there is a sewer line in the next street, digging up about 15mts of our driveway and getting permission to go through the neighbours garden as we are at the end of a cul-de-sac prob worse than digging our own slab up.

Will get some pics and post after dinner.

Thanks
Belinda

 

[MissyB]

Untitled

• MissyB
• 26 May 2008
• 1

Ok, I hope the image works. This shows where we dug at the rear of the extension. There is approx a 6inch concrete footing with the 8inch block on it then the brickwork starts. The DPM sits at the top of the block and thats roughly where the internal slab is. This was the only place hubby was able to dig to see how deep the concrete was as there was alot of concrete about 1ft out from the wall but not solid just appeared to be spilt over perhaps from the footing.

Hubby had a look in one of the manholes and now thinks the carport/garage may not have had a slab pre the extension as the bricks are only 2 courses high, raised from the original level which we think was likely tarmac. All the other bungalows in the street only have tarmac carports.

Does this help? Can you advise any further? You suggested that not having steel reinforcement was not that much of a problem, is this the case as we thought if we dug the chanel up to fix the pipe and found no steel reinforcement we were concerned that we would have to dig the entire slab out and start again but thats because we are going on Aust regs.

Thanks
Belinda

 

[Joe Malone]

We're only dealing with a garage floor here Belinda. I'm pretty sure that there are no requirements for reinforcement in the floor but I'm sure someone will correct me on that if i'm wrong. The picture and what you describe strengthen my initial thoughts that it was installed after the foundations and is a separate slab. You've really got to start and dig it up and see what you've got. As it's only a garage floor why not just patch repair the concrete once the job is done.

 

[MissyB]

Thanks for the reply. Sorry I should have made it clearer that this was a carport/garage. Its now part of the main house and we are about to start making this into Bed 4 / Breakfast room / WC & Utility. At the moment what will be Bed 4 is a workshop with no double glazing or cavity walls so quite cold. The rear section follows on from the kitchen so the fridge, a small breafast table and the washing machine are here. Again no double glazing but double brick walls.

As it's part of the house and we are about to spend quite a bit on it to get the insulation and double glazing sorted that's what worries me about what it should have. Before we dig we just want to know a bit more about UK regs regarding slabs.

If we dig and there is no steel reinforcement will we need to dig out the entire slab?

Thanks
Belinda

 

[Joe Malone]

Hi Belinda, if thats the case then the whole slab will have to come up anyway. I'm very doubtful that the slabs insulated or that it will comply with the requirements in regard to resistance to moisture. Can you get hold of a copy of approved document C? All the technical requirements are in there for floor slabs. I can send you a copy if you have an e-mail address.

 

[Richard C]

Can you get hold of a copy of approved document C? All the technical requirements are in there for floor slabs. I can send you a copy if you have an e-mail address.

Down load a copy for free here:

http://www.planningportal.gov.uk/england/professionals/en/1115314110382.html

Just to chip in, you could be on diminishing returns here & it may be cheaper to knock the whole lot down & start again, especially if you’re planning other works! I had to make just such a decision when considering the suitability of extending into an old brick built car port attached to the side of my 60's property; I didn't have drain problem (as such) but the foundations turned out to be little more than an un-reinforced 8 inch slab of concrete; I did manage to re-use most of the bricks though!