DIY Doctor UK DIY Forums

I am now thinking about laying the concrete flooring. I have laid a plastic membrane on top of polystyrene sheeting (no concrete yet though). Does the plastic membrane need to be tied into the existing damp course of the house? I can quite easily cut out a grove with my steel saw and feed the plastic membrane into existing house damp course (then pack with cement). Also should the plastic membrane also over lap the internal wall of the conservatory and sit under the new DPC that I am going to introduce?

I also have to continue an air brick under the conservatory floor. I am intending on using plastic downpipe, cutting a big hole in the existing air brick and sliding the downpipe inside and under the new floor (to be) to continue the airflow outside and capped with a new air brick. Should I lay the plastic membrane over the top of the downpipe or underneath it? If I lay it underneath it will mean putting the downpipe in direct contact with the concrete flooring and therefore I will have to pierce the plastic membrane by the existing house wall (to feed the pipe though) and then the outside conservatory wall to continue the airflow outside of the conservatory.

Any advise will be gratefully received.

Everthing you described is correct.You dont need to cut the dpm into the house though,just let it lay against the wall.
And Lay the dpm over the pipe for the airbrick.

hi welsh bricky I'm having conservatory done on raft foundation what should I look out for. can you please explain step by step of the foundation to the floor screed. its it dump proofing first and then concrete slab and then hard core and the top of flooring. please give some idea of what to look out for.

1.excavate ground the depth of the foundation depends on ground conditions.
2.If its a raft foundation reinforcing mesh is required the area may also be shuttered with timber
3.building the brickwork to dpc height.
4.laying hardcore and compact with vibrating machine.
5.laying insulation, its usually 50mm thick,then dpm (plastic sheet)
they may put sand down first, then dpm then insulation.
then concrete minimum of 100mm thick.
6.sand&cement screed laid on top of the floor to match the floor level from the house.
the screed may not be nessasary,aself level compound may be used to finish the floor.
7.brickwork to desired height.
8.conservatory fitted
9.dryline the interior&plaster.
10.flooring, Laminate,tiles etc

Thank you very much welsh brickie for the info!
!

hi welsh bricky welsh! I'm having my conservatory done at the moment they already done with the raft foundation and brick wall, my only concern is there is no damp proofing on the floor after they laid the cement on the raft foundation thats it no second layer or as you said it have a hardcore and dpm. can they still do the damp proofing effectively even if the wall is already erected. the second phase now is the installation of the conservatory. can I have some advice on this please

So there is no sign of any dpm (Plastic) is there a timber floor being installed,and airbricks fitted in the walls??There should also be dpc (damp proof course) laid to match the level on the house,usually 2 bricks above the exterior ground level.

Don't forget you can install a liquid dpm which is painted on the concrete.