Insulate concrete porch

[Lindgrenski]

We are planning to convert our concrete veranda into a hall, how should we best handle the floor? Cellplast, grooved particle board with underfloor heating, and then flooring on top? Flooré? Floor plates? We don't want to raise the floor more than 10 cm.
Would I gain anything by insulating the ceiling under the veranda?

 

[huggan]

Polystyrene is the easiest way. It is recommended to insulate from underneath, place 2/3 of the insulation underneath if you can. There are grooved polystyrene boards so you can avoid the particleboard, but you should still use the plates.

 

[Lindgrenski]

Looked at Flooré, which is an aluminum-clad grooved foam board, seems smart. However, I don't know if I can place that board on top of an additional 50mm of foam. I can probably put up a few boards on the ceiling below, shouldn't be any major problems. The question is how much it helps since I can't have any insulation on the sides.

 

[huggan]

You can place it on another disc but it's good if it's the same hardness. If you don't insulate underneath, you get moisture transport through the concrete slab, which is not good.

 

[Lindgrenski]

Do I need any moisture protection like Platon underneath?

What do I build first, the walls or the floor? Is it difficult to attach the sills to/through the foam insulation?

 

[huggan]

If you insulate underneath you don't need platon but you need to measure the slab so it is not too wet. You build the walls first.

 

[Lindgrenski]

If you insulate underneath you don't need platon but you need to measure the slab so it's not too wet. You build the walls first.

If you insulate underneath you don't need platon but you need to measure the slab so it's not too wet. You build the walls first.

It usually drips a bit in the space under the veranda. Otherwise, it's just the outer part that is in contact with the ground 2.50m down, typically.
How do I measure the moisture?

 

[huggan]

You need to borrow a moisture meter.

 

[Lindgrenski]

You need to borrow a moisture meter.

Who has one then? Builders?

 

[huggan]

Floor layers usually have it but some builders do too.

 

[Lindgrenski]

Floor layers usually have it, but also some builders.

Feels like it will be both easier and cheaper to lay Platon. It's only about 8m2.

 

[Lindgrenski]

Or do I need to place Platon under the exterior walls?

 

[huggan]

No, not under the walls.

 

[Lindgrenski]

Talked to my father-in-law who is an old carpenter and he thought we should just put plastic on the concrete and then EPS. But now when I'm searching around, some say that the plastic should be above the EPS?

 

[justusandersson]

If you follow @huggan's suggestion and place the insulation foam on the underside of the concrete, you won't need any additional moisture protection measures. The moisture currently in the concrete comes from indoor air and has condensed (i.e., transitioned from vapor to liquid) because the concrete is cold. If you place plastic on top of the concrete without insulating its underside, there is a risk of condensation on the plastic.