After stripping the original siding from a 30 year old house and preparing to install fiber cement panels a contractor wonders if he can use a waterproof synthetic roofing underlayment instead of housewrap behind the panels.
Roofing felt as house wrap.
Drive staples and trim.
Substituting synthetic roof underlayments for housewrap.
Traditionally metal roofs have used standard 30 pound felt paper underlayment.
When and why condensation occurs inside buildings explains the problems caused by excessive indoor condensation explains how moisture enters building wall and ceiling cavities and summarizes the best approaches to prevention of indoor moisture and condensation problems.
Explain what is wrong with using roofing felt under siding.
The main purpose of the sheathing wrap whether building felt or plastic housewrap is to prevent water leakage into the building structure.
The main advantage of house wrap over felt paper is the superior strength and durability of house wrap.
Asphalt felt tar paper the standard requirement is type 1 felt meeting astm d 226 standards.
The first goal of roofing underlayment is to keep the roof deck dry before installation of the metal roofing material.
Working with a helper install the bottom piece of felt so it extends 1 or 2 inches below the sill.
Here s what an expert had to say.
How to do it install bottom piece.
House wrap and felt paper when properly installed and undamaged are both weather resistant barriers wrb that create permeable and water and air resistant exterior walls.
Underlayment must also act as a secondary weather barrier in case the roof fails.
Then install vertical nailers over the wrapped sheathing and attach the panels to the nailers which will create an air space between the panels and the wall sheathing.
The original wrb was asphalt impregnated felt paper or tar paper the same material commonly used as an underlayment under roof shingles.
No you should not use roofing felt as a house wrap for siding but you can use gaf underlayment call deck armor for wrapping the exterior of a home before siding is installed.
It s both breathable which will help solve problems with moisture and waterproof.
A high quality house wrap like barricade building wrap is more resistant to ripping and tearing during installation than felt paper.
More recently the term house wrap is usually used to describe plastic fabric wrbs such as tyvek.
The use of roofing felt or 15 pound felt as a building house wrap or vapor barrier and the permeability moisture problems and indoor condensation problems that may occur vapor barriers and condensation in buildings.
It is critical therefore to cover the entire shell from roof to foundation including gable ends and band joists and always to lap upper layers over lower layers shingle style to shed water.
First cover the sheathing with asphalt felt or a nonperforated housewrap like tyvek or typar which will protect the sheathing from moisture but also allow the wall assembly to breathe.
