Laying pipes in solid floor (scullery)

[JohnC]

Hi All,

I'm looking for some refurb advice on a property I recently bought. The property is an 1906 Victorian sandstone semi-detached and the majority of the subfloor is suspended timber with the exception of the utility and downstairs toilet. There is also a kitchen extension at the rear of the building which is accessed through the utility. We have plans to move the boiler into the utility room and was considering cutting a narrow track in the "solid" floor of the utility for the pipes to run to and from the boiler. The floor is currently terracotta tile and about 50mm of concrete skim with a DPM under the concrete. Below that seems to just be fill material. There was also chipboard laid on battens over the terracotta to bring this up to the same level as the surrounding rooms.

If I was to cut a track, say 150mm deep, line the track with DPM and overlap and seal this on top of the terracotta would this be enough to prevent moisture coming into the track? I understand the moisture is most likely escaping elsewhere at the moment (potentially through the adjacent walls that the DPM meets). Or would I be better removing all the fill material and lowering the entire DPM in the room? There are airbricks at the front of the house and some at the back on the exterior of the extension, however the utility area has none as it is a solid floor. However I can see an old clay pipe coming through the interior wall of the utility into the dining room and stops as it enters the dining room subfloor (which is suspended timber).I've attached a few pictures of the utility room to give a better understanding of the layout, any suggestions would be greatly appreciated!

Thanks

 

[Cubist]

Hi There and Welcome,

If I was to cut a track, say 150mm deep, line the track with DPM and overlap and seal this on top of the terracotta would this be enough to prevent moisture coming into the track?

Your approach may prevent moisture from the floor/earth/walls bleeding into the trench BUT presumably the pipes you would wish to run through the trench from the boiler would be the main feed and returns to/from the radiator network. Those pipes would typically be 22mm copper and while plastic is an option industry standards do dictate copper for at least the first meter. Whatever these pipes will warm the immediate surroundings in the trench and could induce condensation on the pipes which may then transfer to any surrounding materials - over time this could lead to loss of efficiency of the heating system and/or induce corrosion and failure of joints. In any event it is never wise to bury any kind of service pipe and certainly not in potentially corrosive materials. Maintenance can also become considerably more difficult and expensive. Do you have other options?

Sorry, for the negative feedback but your current strategy, to my mind, suggests a lot of pain for very little gain and perhaps some long term risk.

Cheers for now,
Cubist

 

[JohnC]

Hi There and Welcome,


Your approach may prevent moisture from the floor/earth/walls bleeding into the trench BUT presumably the pipes you would wish to run through the trench from the boiler would be the main feed and returns to/from the radiator network. Those pipes would typically be 22mm copper and while plastic is an option industry standards do dictate copper for at least the first meter. Whatever these pipes will warm the immediate surroundings in the trench and could induce condensation on the pipes which may then transfer to any surrounding materials - over time this could lead to loss of efficiency of the heating system and/or induce corrosion and failure of joints. In any event it is never wise to bury any kind of service pipe and certainly not in potentially corrosive materials. Maintenance can also become considerably more difficult and expensive. Do you have other options?

Sorry, for the negative feedback but your current strategy, to my mind, suggests a lot of pain for very little gain and perhaps some long term risk.

Cheers for now,
Cubist

Hi Cubist, Thanks for the welcome and reply.

The pipes would be the main gas feed and the flow/return for radiators and the domestic hot water for the kitchen. The plan was to leave the trench open and strap over the trench using timber before replacing the subfloor on top, so not actually backfilling the trench. The condensation is a good point, I'm not sure if that would start to affect the surrounding suspended timber floor in the adjacent hallway...?

I have thought about replacing the solid floor in both the Utility/Laundry and the bathroom with a suspended timber floor although more thought would be needed with regards to airbricks and having airflow between the dwarf walls in these new areas.

 

[Cubist]

Good that you were/are thinking of leaving the trench open rather than burying the pipes. that would make some aspects simpler and easier to maintain. You may want to consider re-sizing the trench dimensions to allow room for each pipe to be covered with an insulation sleeve. This would considerably reduce heat transfer from the feed/return pipes and thus also reduce/eliminate the condensation issue. You will though need also to closely examine the location where the pipes would transition through the wall into the house and how that position might accommodate the new pipe layout.

The condensation is a good point, I'm not sure if that would start to affect the surrounding suspended timber floor in the adjacent hallway...?

Would it be fair to assume that the extant heating pipework is surface mounted or do some sections run under suspended floors? Again, pipe insulation below floors can be helpful and indoor condensation at low levels is less likely to be an issue. Also, there are some simple but effective collars that can be installed around a pipes exit through a board to hide any discolouration.

 

[dinosaur]

hhello i had same problem and ran insulated pipes in boxed replacing skirting board with removable lid

 

[paulc]

presumably the pipes you would wish to run through the trench from the boiler would be the main feed and returns to/from the radiator network. Those pipes would typically be 22mm copper and while plastic is an option industry standards do dictate copper for at least the first metre.

Depending on the number and size of radiators, it may be prudent to use 28mm pipe as far as the first few big radiators. Should you ever install a heat pump, it would cut down on the amount of plumbing that would need to be modified - This assumes that the system is already a mix of 22mm & 15mm rather than microbore.

The one concern I would have is these pipes are likely to be the lowest point in the system. Quite possible that sludge would collect in the return and eventually cause a blockage. If the pipes were run above floor level, there is the option to install a drain cock that could be used to flush the system when required.