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(833) 751-2102
Serving Washington County

Flat and Low-Slope Roof Repair in Hillsboro, OR

Repairing flat and low-slope roofs in Hillsboro and the towns around it, starting with the drains and the seams where water collects.

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  • Roof repair and full replacement
  • Moss, wet-season leaks and wind damage
  • Pitched roofs across Washington County

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Flat Roof Repair

Flat Roof Repair: what it covers

Quick answer

A flat roof is built to drain by a slight fall toward its outlets. The repair starts with the drains and low points where water stands, then the seams, blisters and flashing, and the record shows what was done.

Flat Roof Repair illustration for Hillsboro, OR

A flat roof depends on its drains. Its fall is small, and it relies on outlets and scuppers to carry water away. When an outlet is blocked or sits above the low point, water stands in a basin and works into the membrane, and the damage is often out of sight until a ceiling shows a stain.

The FACTS sheet gives no share of flat roofs for Hillsboro, so this page does not say how common they are. Moss and leaf debris are a particular problem on a flat roof under trees, because they block the outlets and hold water on the surface.

This page explains the common flat roof repairs and the order they are done in. The quote lists each line, so the drainage work is visible as its own item.

Service area
Hillsboro & Washington County
Availability
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Warning signs

Signs you need flat roof repair

Do not walk a flat roof in wet weather or near an unprotected edge. Keep off any roof with soft spots, and call the line if the ceiling below is at risk.

  • Water standing at a drain or in a low spot for more than a day after rain
  • Moss, leaves or grit packed around a drain or scupper
  • Blisters or soft spots in the membrane that give under foot
  • Seams that have lifted at the edge or split along their length
  • Cracked flashing where the roof meets a parapet or a unit
  • A stain on the top-floor ceiling directly below a low roof edge
Our process

How our flat roof repair visit works

  1. Walk the roof and map the ponding

    The roofer walks the roof after a dry spell and, where possible, after rain, marking where water stands and how long it lasts.

  2. Clear and check the drainage first

    Drains and scuppers are cleared of moss and debris and checked for height. A drain set above the low point is corrected before the surface is touched.

  3. Probe the seams and the blisters

    Seams are probed by hand and blisters are opened and checked. Wet insulation found under a blister is cut out and replaced rather than sealed over.

  4. Repair with the named product

    Failed seams are cleaned, primed and patched with the product the membrane maker names, and the patch laps the sound membrane as the detail requires.

  5. Test the drainage and record it

    The drainage is tested with a measured flow of water, and the record lists each drain, seam and repair with photographs.

Why does a flat roof hold water after the drain is cleared?

Because the drain may sit above the low point. Clearing it empties the basin only to the level of the drain, and the rest of the water stays.

A drain cleared at the surface can still hold water when its height is wrong. The basin fills to the drain and no further, so clearing changes nothing below that level. The fix is to measure the difference between the drain and the low point, and then to move the drain or form a sump.

Either change is a deliberate alteration, and it is written into the scope with its reason.

  • Measure the drain against the low point
  • Record the pond depth after a dry day
  • Decide between moving the drain and forming a sump

Why do seams fail first?

Because seams are made in the field and age faster than the sheet. When a seam opens, water finds the gap, and the first sign may be a stain well away from the seam.

A membrane is one sheet across the roof, but the seams are where sheets meet, and they age first. Sealant dries and shrinks, and a seam edge lifts. A seam that is intact underneath can still leak at its lifted edge, so the edges are the first place to look.

A roofer probes each seam, marks the failed ones on a numbered plan and repairs them with the product the membrane maker names.

  • Probe each seam along its length
  • Mark failed seams on a numbered plan
  • Use the named product on a clean, dry surface

When is a repair not enough?

When the ponding covers most of the roof, the membrane splits when lifted or the insulation is wet across a large area.

A repair is right where the damage is local and the membrane is flexible. If ponding covers most of the roof, the membrane splits or the insulation is wet over a large part, replacement is the honest question. The roofer says so in writing and explains the options.

A replacement is a separate quote, and this page covers the repair only.

  • Ponding across most of the roof
  • A membrane that splits when lifted
  • Wet insulation over a large area

What belongs in the flat roof record?

The drains by position and height, the seams by number, the repairs made, the materials used and the drainage test after the work.

A flat roof record names each drain and scupper, states the height found and the height after any change, and lists the seams and repairs by number. It records the test and the materials used. Photographs before and after show the roof at each visit.

Keep the record with the roof file. A roof with a documented drainage history is easier to maintain and to insure.

  • Drains named by position and height
  • Seams numbered and repairs listed
  • The drainage test after the work

Why a low-slope roof behaves differently in a wet season

Because a low-slope roof sheds water by its small fall and its outlets, and a wet season tests both. A blocked outlet in the wet months becomes a pond that the membrane must carry.

A low-slope roof has little fall to work with, so it depends on its outlets. In a wet season the outlets collect moss, leaves and grit, and the pond deepens faster than in a dry one. A deep pond adds weight and presses water into any seam that is already open.

The roofer clears the outlets before the wet season and checks them after the first heavy weeks. A drain set above the low point is recorded, because it will hold water every winter until it is moved.

  • Clear the outlets before the wet season
  • Check them after the first heavy weeks
  • Record any drain set above the low point

What a drain repair does to the membrane

The membrane is cut around the drain, the new flange is sealed to the membrane and the lap is tested before the surface is closed.

Moving or replacing a drain means cutting the membrane around it, and the new flange must be sealed to the sound membrane with the product the maker names. The lap is tested by hand and with water before the area is closed.

The record shows the cut, the flange and the test, so the next roofer can see the work and where the membrane was altered.

  • Cut around the drain carefully
  • Seal the new flange with the named product
  • Test the lap before closing the area
Options

Types and options for flat roof repair

Drain and scupper correction

Clearing, re-setting or replacing outlets. Often the cheapest flat roof repair and the one that prevents the next leak.

Seam and membrane patching

Repairs to single-ply or modified bitumen seams, and patches over splits or blisters.

Insulation and deck replacement

Wet insulation or decking under the membrane is replaced, added to the quote only after the wet area is shown.

Washington County

Why flat roof repair is different in Portland metro

The FACTS sheet gives no share of flat roofs for Hillsboro, so this page does not state how many buildings the work applies to.

Flat roofs under trees in the wider Washington County area are cleaned of debris more often than roofs in the open, and the roofer sets the check interval on the record.

The Portland-side towns, including Beaverton and Tualatin, are repaired on the same method, and the travel is shown on the quote.

Skip the guesswork. Call for a straight answer.

Tell us what's happening and we'll tell you honestly whether it's a quick fix, and what flat roof repair should cost.

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Where we work

Flat Roof Repair across Washington County

Not sure if you're covered? Check your ZIP code.

Related

Roof Decking Repair

Replacing damaged roof sheathing in Hillsboro and the towns around it, sheet by sheet, so the new covering sits on a sound deck.

Flashing and Chimney Repair

Repairing the flashing at chimneys, walls, vents and skylights in Hillsboro, where moss, debris and wind most often open a roof.

Windstorm Roof Inspection

A written roof inspection after a windstorm in Hillsboro and the Washington County towns, with wind damage separated from moss and wear.

FAQ

Flat Roof Repair FAQs

Can a flat roof be repaired without replacing it?

Often, if the deck and insulation are dry and the failures are at drains, seams or penetrations.

How soon should ponding clear?

Within a day or two. If it does not, call a roofer, because the cause is usually the drain or the roof's shape.

Should I clear the drains myself?

From the ground with a long tool, if it is safe. Do not reach over the roof edge.

Will a repair void the membrane warranty?

It can, depending on the manufacturer and installer. Ask for the terms in writing before the work.

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