Isoleren dak wooden roof

[Rdougan]

Hopefully some of you helpful folks will be able to help this English speaker in Haarlem. Thanks in advance!

I have been doing renovations to our house here in Haarlem since December (bought the house in September 2013). The bottom floor is a large garage, and the back part of that is a terrace on the first floor.

It is difficult to get information in English as this design is not common in the UK or US. Normally, if you have a flat roof, you would not have a decking on it. I am trying to learn Dutch, but it is not so easy. :)

Picture when we bought the house:

Picture in it's current state:

The roof was never insulated as it was always a cold room (no heat). There are no leaks. I'm not sure of the material, but I believe it is bitumen.

We plan to install a large skylight at the back (5x1m), and we also need to insulate the roof. I am wondering is the current coating OK, or should I replace it with something better? Or will I simply cut out the hole and coat the pieces around the skylight?

If I can keep the coating, how to insulate? Can I just add some isolatie from below, rockwol or similar. Or is it no so simple?

And finally, could anyone suggest, or let me know what the name is for a contractor to check the structural rigidity of the roof? I would like to know how much weight it could witthold (maybe a hot tub? tegels?)

Dankjewel!
Robert

 

[IJkenhout]

Is it a wooden roof or concrete?

You better ask a roofer (dakdekker) to check if the roof is still ok. It's better to insulate from above. Even a "reverse roof" (omgekeerd dak) is better. Then the insulation is on top of the bitumen.

If insulation from the outside is not possible, you can insulate from the inside. Than a foil (dampdichte folie) is necessary to keep the moisture out of the roof.

A constructional engineer (constructeur) can be asked to check if the construction of the roof is sturdy enough.
A contractor is a (aannemer).

 

[Rdougan]

Thanks!

The roof is wooden. Wooden joists, then wooden cross beams under the bitumen.

I will contact a dakdekker to see what they say about the structure.

When would insulation from the outside not be possible? Because of costs (because you would have to re-lay the bitumen)?

I will look into omgekeerd dak and dampdichte

 

[IJkenhout]

When the bitumen is pretty new, than it's not cost-effective to renew it with insulation. Mostly it is possible. Check if there is space near doors en roof edges for the extra height of the insulation.