roofing... new layer on top of old.

[kellyj00]

I have a three-tab asphalt shingle roof that I would like to re-roof myself. I've heard it is ok to just put asphalt shingles on top of the old (so you don't have to scrape up all the old shingles) as long as it doesn't go over three layers deep. Is this true? If so, should I be putting down tar paper on top of the old shingles before laying the new layer?

Also, is there any disadvantage of going with fancier asphalt shingles than three tab? I've seen some neat stuff from home depot (manufacturer GAF) that look really neat, but are definitely not three tab design.

[CJT]

Some localities have regulations affecting this.

I'd take off the old roof.

[Eric in North TX]

It has been done for years, not popular in my area as high winds are common, and the physics of the longer nails isn't as good.

The Timberline type shingles are an advantage especially for an amateur roofer; as they ares so asymmetrical to begin with that mistakes show up less.

[Edwin Pawlowski]

Many codes allow only two layers. I'd not try for three, but it has been done. More likely to have problems down the road. If you have curling shingles, definitely get rid of them.

I prefer the look of the "architectural" style over the three tab. No disadvantage at all.

[Frank]

When roofer added new shingles over old several years ago, old shingles were curled somewhat and he recommended textured type shingle to help hide any imperfections. Looks great.

Reason for not doing more than 2 layers is excessive weight on roof.

Frank

[Tom The Great]

Before you even think about it, find out if it allowed by local codes. Some places don't want that much fire fuel on your roof. So one layer might be the limit.

later,

tom @

[bamboo]

[kellyj00]

what's better than 15lb felt?

[krw]

Ice and water shield?

[Eric in North TX]

Almost anything, but then, I hate that stuff.