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What fails on a house, why it fails, and what it should cost

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Roofing · Before you get quotes

Roof over an addition with a different pitch

Additions on old houses commonly meet the main roof at an awkward transition, and that junction is where leaks concentrate. Point it out specifically when getting quotes so it is priced rather than improvised.

More on pre-1940 roofs
Quick answerWhere an addition’s roof meets the main roof at a different pitch, water changes speed and direction, and the flashing has to handle an awkward joint. That junction is where leaks concentrate. You can handle this one yourself. No call needed: find the transition, check for signs of leaks, and name it in every quote so it’s priced rather than improvised on the day.

This is most common in homes built before about 1940. Many old houses gained a back room, a porch enclosure or a kitchen addition decades after they were built. The addition’s roof was often built at whatever pitch fit, not the pitch of the main house.

1Why the junction leaks

  • Change in pitch. A steep slope running onto a shallow one dumps fast water onto a surface that drains slowly.
  • Improvised flashing. The joint between the two roofs, or between a roof and a wall, is often flashed with whatever was at hand.
  • Low slopes. If the addition’s roof is very shallow, standard shingles may not be the right material. Check what the shingle maker allows.
  • Different ages. The two roofs may have been built and reroofed at different times, with different materials.

2How to check it yourself

  1. Find the transitionFrom the ground, find where the addition’s roof meets the main roof or the main wall.
  2. Look at the jointWith binoculars, look for heavy patching, tar, sealant, lifted shingles or rusted metal along the joint.
  3. Look inside below itStains on the ceiling or wall right where the addition joins the house point at the junction.
  4. Note the pitchIf the addition roof is noticeably flatter than the main roof, mention it so contractors can confirm the right material.
  5. Name it in every quoteAsk each contractor to describe how they will flash the junction and to price it as a line item.
Doing it yourself

This is all looking from the ground and from inside. Don’t walk on a low-slope roof or the joint itself to inspect it.

3What to do with what you find

What you handle

  • Find and photograph the junction
  • Note any interior stains below it
  • Ask for the junction to be described and priced in writing
  • Compare quotes on how they’ll handle it

What the crew does

  • Remove improvised patches
  • Install proper flashing at the junction
  • Use a material suited to the addition’s pitch

4What drives the cost

The junction itself is a small part of a reroof, but the cost moves if the addition’s roof is too shallow for shingles and needs a different material, or if the deck at the joint has rotted from past leaks. Getting it named in the quote keeps it out of change orders.

Roofing cost

5Questions

Why should I point it out if the roofer will see it anyway?

So it’s priced and planned, not improvised on the day. Naming it also lets you compare how each contractor will handle it.

Can shingles go on a very shallow addition roof?

Shingles have a minimum pitch. Below it, a different roofing material is used. Ask the contractor what the pitch is and what they recommend.

Written by Jaylan Jones. I Like To Exterior Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.