Why do I need an underlay carpet for soft shingles?
Is it necessary? Can this underlayment be avoided and save money?
Answers
Under the laying of the soft shingles is equipped with a continuous crate.
This can be OSB (is oriented chipboard, sheet material from wood chips), or moisture-resistant plywood, plywood is glued wood veneer.
Or, as the basis is used board, which is attached practically to the joint, but with a small gap.
That is, in any layout between the sheets of OSB, plywood, or between the boards are seams (compensation).
That same "underlay carpet" does not allow soft shingles (and when exposed to high temperatures, the surface of the roof is heated in the sun, if simpler, it becomes very elastic) to repeat the outlines of those same seams.
Plus underlay carpet can further level the base on which the shingles are laid.
And plus it can act as additional noise insulation, to put it simply, the noise of rain will not be heard, although this is not the main indicator, but something like "extra bonus.
This is especially true with large areas and not enough quality laid (with gradients) solid battens.
Next, "underlay carpet" is also an additional waterproofing material protecting the roof from leaks.
But it is important to consider that the same "underlay" carpet is not the only waterproofing material in the "roofing pie.”
In addition to the "underlay carpet" there is another layer of roll-seal waterproofing (under the continuous furring) protecting the insulation from moisture, we are talking about mineral wool.
The whole "pie" looks like this:
Soft shingles, under it "underlay carpet", then continuous battens.
Under the furring roll waterproofing, then insulation and insulation from the room (attic or loft) is set as a vapor barrier.
As you can see "underlay carpet" must be present in the "roofing pie," if of course the quality and durability of the roof.
Faced with a variant of laying shingles without an underlay mat, the customer is in this economy, but the durability of this roof is questionable. In my opinion, do not save on the underlay mat.
There is a roofing felt "armored", i.e. sprinkled with stone chips on the outer side.
This allows you to strengthen it, make the color lighter, so that it is not so heated in the sun, so that, being in a roll, it does not stick during transportation, etc...
According to modern technology, it must be glued to the mastic, applied on the "underlay" soft roofing felt.
It is beneficial to the manufacturers, so that instead of one roll you buy two. The same story with soft shingles, but has a place to exist, because. One – it strengthens the thickness of the roof. Second – the first layer will be solid. Third – does not spoil the appearance of expensive soft shingles. Fourth – a guarantee of waterproofing coverage.
I would, in the case of conventional roofing felt, not buy a substrate, and for soft shingles I consider its use is necessary. It's up to you to decide.
