Wood Repair and Substrate Priming Standard

Purpose

Get every bare, repaired and replaced piece of wood on the job to a sound, dry, fully sealed condition before a topcoat touches it, and decide honestly which pieces are past repair. Two failures come out of skipping this. Filler troweled over decay that was still soft gives a patch that pushes off the wall in a year with the rot still growing underneath, and bare wood left open past its priming window, or primed on the face only, wicks water through the back and end grain and peels the new coat off in sheets while the front looks perfect.

Scope

Exterior and interior wood on residential and small commercial buildings: siding, trim, casing, sills, fascia, rake, corner boards, columns and porch members, covering decay assessment, the repair-or-replace call, epoxy consolidation and filling, replacement piece preparation, and the priming of all bare wood.

It does not cover structural framing repair, which goes to a carpenter or an engineer, the wash and drying that precedes exterior work (exterior wash and prep day standard), joint sealant renewal (caulking standard), the meter method behind a moisture number (moisture and adhesion testing standard), or paint removal on pre-1978 substrates, which is RRP work (RRP containment standard).

Roles and responsibilities

Procedure

1. Probe and map every suspect piece before deciding anything. Press a blunt awl or a stiff probe into each suspect area at moderate thumb pressure, working the ends, the bottom edges and any joint where two members meet, since those wet first. Acceptance: record each area as sound if the probe does not enter, degraded if it enters up to a shop default of about 1/4 in, and decayed if it goes deeper or the member gives. What wrong looks like: a piece that looks sound because its paint film is intact while the probe drops in with no resistance behind it. Stop rule: any structural or load-carrying member that gives under the probe stops this SOP and goes to a carpenter, because a painter's filler is not a structural repair. Hazard: probing porch and rail members can put weight on something already failed, so nobody leans on a rail or a column to reach, and the ladder carries the weight rather than the building.

2. Make the repair-or-replace call against the map, not against the schedule. Repair pieces that read degraded and are dry, sound behind the degraded zone, and small enough to be filled without becoming the member. Replace where the decay passes half the member thickness, where the piece has a joint that can be opened cleanly, or where the same area has already been filled once. Acceptance: every mapped area assigned repair, replace or monitor in writing, with the reason. What wrong looks like: a sill filled for the second time in three years, which is a replace that keeps being deferred. Stop rule: a piece moving from repair to replace goes to the customer as a change order the same day, before it is cut out. Hazard: none, a decision made off the map.

3. Cut out and remove failed pieces with the assembly understood first. Identify what the piece carries and what sits behind it, cut with a blade depth set to the piece thickness, and pry rather than lever against neighboring trim. Acceptance: the piece comes out with sound substrate exposed behind it and neighboring members undamaged. What wrong looks like: a fascia removed to reveal soaked sheathing, which is a different job than the one you priced. Stop rule: wet or decayed material behind the piece stops the work and goes back to the customer with the source question before anything new is installed. Hazard: cavities carry cables and the cut is blind, so a shallow first pass and a look come before a full-depth cut; if a blade contacts a cable nobody pulls it free, the area is cleared, the circuit goes off at the panel and an electrician assesses before work restarts.

4. Prime replacement pieces on every face and every cut end before they go up. Coat the back, both edges, both ends and the face of each new piece with the primer selected at step 7, and re-prime any end cut made during fitting. Acceptance: no bare wood visible on any face of the piece at installation, including the freshly cut end. What wrong looks like: a new board primed on the face only, which drinks through its back. Stop rule: a piece cut to fit after priming does not go up until the new end is primed, even if that means the piece waits for the dry time. Hazard: cutting and sanding wood, and especially preservative-treated wood, puts wood dust into the breathing zone, and wood dust is a recognized respiratory hazard rather than a nuisance, so cutting is done outdoors or with dust collection at the tool and any respirator is worn under a written program per 29 CFR 1910.134.

5. Consolidate and fill repair areas to the product's own label, in that order. Remove all soft material back to sound wood, apply the consolidant where the label calls for it and let it penetrate, then fill in the lifts the filler's label specifies rather than one deep mass. Acceptance: the filled area is proud of the finished profile before shaping, hard to a thumbnail at the label cure time, and shows no soft spot when re-probed. What wrong looks like: a filled area that dents under a thumbnail hours after the stated cure, meaning it was mixed off ratio or applied cold. Stop rule: a soft fill is dug out and redone, never sanded and primed; and if the second attempt is soft the product or the temperature is wrong and the piece goes to replace. Hazard: epoxy resins and their amine hardeners are skin sensitizers and the hardeners are corrosive, so chemical-resistant gloves and sealed eye protection go on before the parts are opened, contact is washed off with soap and water rather than solvent, and once someone is sensitized further contact provokes a reaction at low exposure, so a tech who develops a rash comes off the product and gets medical evaluation.

6. Shape, sand and confirm dryness before any primer goes on bare wood. Shape the cured fill to the original profile, sand the transition, then take moisture readings on each repaired and each bare piece per the moisture standard. Acceptance: a profile that matches the neighboring run when you sight along it, and a reading at or below 15 percent on every bare wood piece, taken at the wettest point rather than a convenient one. What wrong looks like: an average taken across a piece that hides a wet end. Stop rule: any single reading over the gate holds that piece, whatever the rest of the elevation reads. Hazard: power sanding filler and old coatings generates dust in the breathing zone and grit into upward-facing eyes, so sealed goggles and dust collection at the tool; on a pre-1978 substrate this abrasion is a regulated renovation under 40 CFR 745 Subpart E and stops here for a certified renovator and that rule's containment under the RRP containment standard.

7. Prime all bare wood inside the primer's own recoat window, with the primer matched to the wood. Choose a stain-blocking primer where tannin-rich woods such as cedar and redwood are exposed, a bonding primer over hard slick surfaces, and the primer named by your topcoat's data sheet elsewhere; give end grain and cut ends a second pass. Acceptance: full hiding of the bare wood with no visible starved areas, end grain wet out enough that it does not drink a second application, and the topcoat applied inside the recoat window the primer's label states. What wrong looks like: brown bleed showing through white primer on cedar within a day, which is tannin the primer was not chosen to block. Stop rule: bleed means the correct blocking primer goes on next, not a heavier topcoat; and primed wood left past its stated recoat window is scuffed and re-primed rather than coated over. Hazard: solvent-borne and shellac primers give off flammable vapor heavier than air, so ignition sources near the work go off, work stays out of confined bays without ventilation, and solvent-wetted rags go into a closed metal container because they self-heat and can ignite in a pile.

8. Release each piece in writing, with the repair class it ended in. Record each piece as repaired, replaced or monitored, with its final moisture reading, primer used and priming date, and confirm anything removed for access is back. Acceptance: every piece on the step 1 map has a disposition, a reading and a primer entry, and the count of pieces removed for access equals the count re-installed. What wrong looks like: a map with fourteen mapped areas and eleven dispositions. Stop rule: a piece with no disposition is not released to coating; it goes back to the lead. Hazard: none, it is a desk step, and it is called out because the map is worthless if it is not closed out.

The record this produces

Per job: the step 1 probe map with each area classified; the repair-or-replace decision and the reason; change orders raised for pieces that moved to replace; consolidant and filler products with cure times; back-priming confirmation on every replacement piece; final moisture reading per piece; primer product, date and whether the topcoat landed inside the recoat window. The probe map is what a customer sees when they ask why a sill was replaced, and the back-priming line is what answers a peeling call on a piece that is only two years old.

One run of this procedure, filled in

A 1998 two-story exterior repaint, south elevation. Step 1 probed 14 areas: 9 sound, 4 degraded at up to about 1/4 in, and 1 window sill where the probe went in past 1 in with no resistance and the member flexed under hand pressure.

That sill fails the step 1 acceptance outright, so the stop rule chain ran. The sill was not a load-carrying member, so it did not go to a carpenter, but at step 2 it met the replace criteria twice over: decay past half the thickness, and a filler ridge from a previous repair. It moved to replace, the change order went to the customer that afternoon, and it was cut out the next morning. Step 3 exposed sound framing behind it with no wet sheathing, so the work continued.

Step 4: the replacement sill was primed on all six faces before installation, and the end cut made during fitting was re-primed before it went up. Step 5 handled the four degraded areas with consolidant and filler to the label, in two lifts on the deepest one; all four were hard to a thumbnail at the label cure time and re-probed with no penetration.

Step 6: readings on the five bare pieces came in at 12, 13, 11, 14 and 19 percent, the 19 on the lower end of a fascia return that sits behind a downspout. Against the 15 percent gate that is one piece held, not an elevation held, and it was not averaged: the mean of those five is 13.8 and would have released a wet piece. The fascia return dried two more days and read 13 percent before priming.

Step 7: cedar trim took a stain-blocking primer, the balance took the primer named by the topcoat data sheet, end cuts got a second pass, and the topcoat landed inside the stated recoat window on every piece. Step 8: 14 mapped areas, 14 dispositions, 9 monitored, 4 repaired, 1 replaced.

References

• 29 CFR 1910.134, OSHA respiratory protection, which gates every respirator behind medical evaluation, fit testing and a written program.
• 40 CFR 745 Subpart E, the EPA Renovation, Repair and Painting rule, where sanding or removal disturbs pre-1978 paint.
• Epoxy consolidant and filler labels and safety data sheets, the binding authority on mix ratio, application temperature, lift thickness and cure time.
• Primer technical data sheets for tannin blocking, bonding and the stated recoat window over bare wood.
• See related: the exterior wash and prep day standard, the moisture and adhesion testing standard.