Peter_in_Hungary

A layer of soil/sand in the attic is quite common in older houses. Removing it would remove some loading off the timbers - but if the timbers can't take the load now but could when it was built then IMO there will be other problems that removing the soil would only provide a temporary solution. The tiles I suspect will have no roofing felt under them so the attic will be quite draughty (a good thing for the timbers), the soil will stop the airflow from house to attic and so stop a lot of heat loss. The removal of the soil is a lot of work and mess and if the timbers are sound then you can insulate over, however if there is no roofing felt there is the danger of snow being blown into the attic and whilst the soil can take a bit of snow it is not the same for insulation, if you get lots of snow, with the soil at least you can shovel it out. At the moment you will be able to walk across your attic, if you insulate, unless you put up-stands as described above then you will not be able to do this. So bottom line you can take the soil out and replace with insulation or you can insulate over the top but there are considerations to the decision.

Jack_Russells4ever

There is a couple of deteriorating timbers that need to be replaced in the near future and we thought, when we have the roof replaced we will remove all the soil and replace the 2 bad timbers and then install something like rock wool in its place and also install some wood decking over that to permit walking on a solid surface in the center of the attic, we have no intention of turning the space into living space.

We don't get normally huge snows so that may not be an issue but we did think about possibly installing decking under the new roof tiles and of course some sort of vapor barrier.

Peter_in_Hungary

If you are going to replace the roof then other options arise. The new roof will have roofing felt and you can insulate at the rafters to give you an attic that is within the heated envelope which is a much more useable space. At that point it would make sense to remove the soil and board over the attic floor to give a flat surface (because I suspect that your existing ceiling boards are overlapped). Even if you don't intend to use the attic as living space having the attic warm is better and insulating at the rafters, whilst it uses more insulation won't be more expensive than insulating at floor level and then putting in decking to enable you to walk on it.

Regarding snow, it is not the amount of snow that matters it is the wind that can come with it that causes the snow drifts in the attics.

Jack_Russells4ever

Good points Peter, Thanks much for your insight, we definitely have some things to consider. Would we still be able to use the rockwool if we insulated the rafters? Or should be possibly consider using SIP? Under the roof tiles.

wolfi

A bit OT:
Peter is right - but we did take one more step.
When we realised we needed a new roof the builder brought up the idea of raising it around a meter and thereby winning enough room for a new apartment under the insulated roof.
There was however one thing, very important!
To distribute the load of the new stuff there had to be built a ring of steel reinforced concrete on top of the old walls.
So now we live in this new apartment - while the old house below is reserved for family and other guests who visit us.

Peter_in_Hungary

The reinforced concrete ring is standard building procedure now in Hungary, even on new build. Apart from stabilising old walls and distributing the roof load it is needed because of the modern way of constructing the roof timbers.

What do you mean by SIP? To me a SIP in building terms means a Structural insulated panel which is a prefabricated wall panel which as the name suggests supports the building loads and provides the insulation and is craned in one wall at a time.

Insulating under the tiles creates a warm roof, - that is all the roof timbers are within the heated envelope and the insulation, or the majority of it, is above the rafters. See Timber Frame Warm Stud Ignore the timber frame wall bit of the diagram it is the roof part that is relevant. This type of construction needs attention to detail and I would not expect the typical Hungarian roofer to be able to cope because it will be too far outside their comfort zone.

The usual option is a cold roof, called so not because the roof is cold but because the timbers are not inside the heated envelope. This is the typical roof in Hungary where the insulation is between and below the rafters. (It is also called a cold roof when the insulation is between or/and on the joists. When the insulation is between and under the rafters then usually spacer timbers are screwed to the rafters to give sufficient depth to provide the required insulation and then plasterboard is fixed to the spacer timbers BUT there needs to be a vapour control layer (aka a plastic sheet) between the plaster board and insulation and a breathable membrane under the tile counter battens. With the between and under insulation the insulation under the rafters is run counter to that between the rafters to mitigate cold bridging.

I would not use rockwool slabs between the rafters as the fit has to the very good to avoid cold bridges and it is much easier to get a good fit with standard glass fibre wool insulation.

Jack_Russells4ever

Structural insulated panels can be used for roofing also, you do have to crane them in place. Obviously you would need to have framing in place to fasten them to. Once installed roofing tiles, sheet metal panels or other roofing products can be applied.