Gassy smell in house - Gassy smell in house

[cbt01]

I have a really strong nauseous odour that has started in my house. The house has suspended floors, which we have insulated with kingspan insulation between the joists, leaving the void underneath clear and ventilated. But now there is a really strong smell in one room, like a methane type smell. The house was a self build 25yrs ago, and we have just completed renovating it 8 weeks ago. There was no smell before renovating/insulating the house. The soil stack is at the rear of the house with all the gullies running into each other to the septic tank and soakaway. Can anyone suggest any possible causes or solutions??????

[flowjoe]

There could be a few reasons especially if you have had recent works carried out.

An external blockage should not allow smells into the property if everything (toilets, bath, sinks) have traps on them, but a blockage could well cause water loss from the system into the sub-floor.

Has the recent renovation works involved moving the plumbing around, has an open vent been left into the property by moving waste pipes without capping the old ones off ?.

Start outside and lift the septic tank lid and any manholes, then its time to get somebody into the sub-floor for a look around, if the sub-floor is wet carry out dye testing on the drainage system.