Osb like all other wood will expand when exposed to moisture and i assume the contractor spaced the panels the required 1 8 along the 4 edges and installed h clips along the 8.
Is it ok if roof felt gets wet.
Having wet sheathing covered with tarpaper or membrane will trap the water in the sheathing very bad practice and contrary to industry standardss for roofing.
That s why planning is so important during a roof installation.
Felt will often get wet with a cedar shake roof since this type of roof is designed to soak up then shed water.
It is safe to walk on.
Roofing felt should ideally be dry when shingles are installed to avoid ripping but it s still possible to install when wet.
The decking sheathing should have been tarped and work stopped as soon as it was evident enough rain was going to fall to wet the wood or water barrier felt.
During clear 70 degree days we have more flexibility in our schedule.
Any moisture trapped in the roof will flow down and out.
Roofing felt that has gotten wet can be covered with shingles as long as it is allowed to dry out first the surface underneath did not get wet and it did not wrinkle bubble or rip.
However when the rainy season is here we make sure to work quickly efficiently and safely.
The bubbled felt can cause a minor lump on the finished roof depending on what sort of roofing you re using.
When the felt gets wet it will crinkle up and not lay flat which may not be noticed if you have a thick comp shingle 30 year.
This shortens the effective life of the shingles and can adversely affect the roof sheathing.
The felt collects and then repels the water allowing the roof to breathe.
So yes roofing underlayment can get wet.
Certainly it would have been better to have covered the roof with a tarp or roofing felt before it rained.
Waterproof roofing felt gives the roof temporary protection from rain while you apply shingles tiles or other roof coverings.
But not for long periods of time.
Roofing felt is not designed as a permanent exterior barrier against water.
Roof replacement is expensive.
I ve tried covering the roof to protect from rain with plastic or.
This moisture can lead to mold and mildew forming underneath the shingles.