Paper roof on a functional house?

[C_N]

Planning to build a functionalist house with a low slope on the roof. Is it possible to choose a felt roof to reduce costs?

Is felt a good material?
How long does it last?
Are there any problems with felt?
Is it difficult to repair if it gets a hole?

Thanks!

 

[Hene]

Now I hope that more knowledgeable people will answer the question later, but I can start since I have at least talked to someone who claimed to be an expert about this as I have a similar project going on and where papptak was what I got.

If there is a very low roof pitch, papp is not just a good material, but the best (depending on which papp, of course).
This is reportedly because tiles are too heavy for low-pitch roofs and metal moves too much when it gets a heavy load, which it does on a low-pitch roof in winter. When the metal moves, the holes widen, and water gets in.

A proper papptak lasts about 30 years.

Problems can arise if there are holes when shoveling snow, and reportedly it is difficult to lay yourself if there are pipe penetrations because it is hard to get it watertight, but a roofer should be able to fix it.

I dare not say more.

 

[Skumpen]

Laying felt on a roof with a small pitch is like asking for trouble, I would say the durability is 15 years and it's the sun that causes cracks in the felt which is the biggest culprit.

 

[pjkw]

If the angle is sufficiently low, then cardboard is the only option, right?

 

[Skumpen]

Double-seamed sheet metal roofing is probably the best, and it lasts a lifetime and looks nice too, even if it costs more.

 

[Hene]

Double-standing seam sheet metal roofing is probably the best and it lasts a lifetime and is also nice looking, although it costs more.

As I said, I only have the word of a roofing guy to go on, but the person I spoke with claimed that sheet metal roofs on roofs with too low a slope (below 11 degrees, I think he said) don't work because the metal moves and widens the holes where the screws are. Is he wrong then?

 

[Johan Gunverth]

If a ridge of snow forms on a gently sloping roof, a small lake with water can occur. It then creates water pressure on the seam, which not even double-folded sheet metal can withstand, let alone roofing felt. Länsförsäkringar required fully welded (stainless) metal on roofs with less than a 4° slope. So it had to be on my roofs under the balconies. Extremely expensive, but as mentioned, a requirement.

 

[Skumpen]

In double-lock standing seam roofing, no screws or nails are used.

 

[Eld]

The reason you can't lay tiles on roofs that slope less than 14 degrees is simply that the water doesn't run off properly. Some of it will run around the edge of the tile and under the roofing tile. It has absolutely nothing to do with the weight.

 

[Hene]

In hene in double-folded seam roofing, no screws or nails are used

I think the TS should disregard my answers in this thread. Not a single correct figure so far. But I have learned a couple of things and I am thankful for that.

 

[Jan-Å]

What the sheet metal workers have told me about metal on roofs with a slight slope is that water can leak into the seam, which is why I have always laid whole sheets so that there are no transverse seams. I have used tp20 on both the residential house, garage, and patio, slight slope with an original felt roof. Easy to lay, doesn't weigh much. So far, I haven't had any leaks, but I did have both the garage and patio covered with only raw wood boards + underlay felt during a week of hysterical rain without any leaks anywhere at all, so then it should be sealed with the metal, I guess

 

[jocke_mejsel]

Paper or sheet is the only thing you can put on roofs with slopes under 3 degrees, and a paper roof lasts at least 40 years if properly installed.

 

[andersmc]

So far, no leaks but I had both the garage and the patio covered with only raw wood + underlay felt during a week's hysterical rain without any leaks at all, so it should be tight with the metal on, I guess

As long as it only rains fairly straight down, the water usually runs off. Problems start when it blows enough for the rain to drive sideways, or when you have large accumulations of melting snow on the roof.

 

[titanium]

I am planning to build a functionalist house with a low roof pitch. Is it possible to choose a paper roof to reduce costs?

Is paper a good material?
How long does it last?
Are there any problems with paper?
Is it difficult to repair if it gets a hole?

Thanks!

Paper is nowadays a very good material and often the only material if one is to lay the roof oneself. It lasts at least 30 years, but the new paper materials last even longer. The problem is, as with other materials, one must be extra careful with low pitches. Incredibly easy to repair if there should be a hole.

I have myself laid paper on the house, small cabin, and summer cottage. All with low pitches, 5 to 14 degrees. The first roof we laid was with the old technique - hauling up hot "tar" onto the roof. Troublesome and time-consuming. The second roof was with professional paper and a propane torch. Very smooth and guaranteed tight. The latest was with pre-glued paper. Incredibly smooth and easy. Carefulness at seams is, however, extra important.

The first "tar roof" is soon due for replacement, and it has been in place for 25 years.

If I were to lay a roof today with a 5-10 degree pitch, I would choose double-seamed for extra lifespan. Though very expensive as you have to hire a roofing company. There is indeed seamed roofing that one can lay oneself from 8 degrees, but if there are penetrations on the roof, I would avoid this. If I were to do the job myself, I would lay self-adhesive paper of the highest quality. Or if from some roofing company one can get hold of professional paper for propane laying, I would primarily choose this option.

 

[Jan-Å]

As long as it only rains fairly straight from above, the water usually runs off. The problems start when it blows to the point that the rain drives sideways, or when large gatherings of melting snow are on the roof.

But how often does that happen? There is felt under the metal that takes care of any water on the few occasions it happens. But it is correct that the seam is the problem with a metal roof, especially in strong winds.