Keeping Rats Out: An Exclusion Guide for Fremont Houses

Why exclusion is the step that lasts

Devices remove the animals that are present, but an opening they used stays open until it is closed. Exclusion removes the route, so a new animal finds the house closed.

A trap that catches a rat removes one animal. The gap the rat used remains, and the next animal that finds it will come in as the first one did. Exclusion is therefore the step that stops the cycle of catching and returning.

The work is done in the same place the identification and the runs have shown. A closure placed on a route the rats do not use is wasted, and a closure placed on a route they use stops the return.

Which openings to check on a Fremont house

The openings are at the roof line, the eaves and the soffit, the gable vents, the rim joist, the utility penetrations, the garage door seal, the threshold and any gap under a shed or a gate.

At the roof line, the soffit vents and the gable vents are the usual openings. A torn screen or a missing one is a route. The eave where the fascia meets the roof is checked from a stable position, and any branch that touches the roof is recorded.

At ground level, the rim joist where the foundation meets the framing is checked, along with the weep holes in brick veneer and the penetrations for cables, pipes and gas lines. The garage door seal and the threshold are checked along their full width.

What materials to use, and how to fix them

Metal mesh is fitted over vents and small openings, and sheet metal is cut to cover larger gaps. Both are fixed with fasteners into sound material and sealed at the edges. Foam is used only behind the metal.

A plate or a mesh that is fixed loosely is chewed around. The fixing matters as much as the material. The mesh is fixed on at least two sides, and the plate is screwed into sound wood, not into rot.

The foam is placed behind the metal to fill the space and to keep out draughts. On its own, foam is gnawed through, so it is never the only barrier. Exposed foam is covered where sun can reach it.

The order of the work

Close the openings in the order the routes require: the ones used most often first, then the ones that feed them, then the rest. Closing a route in the wrong order can push the animal into an opening that is still open.

The identification and the runs show which openings are in use. Those are closed first, then the openings that connect to them. An opening that the animal has used only once, or that was found by chance, is closed in the last stage.

A sealing plan written as a list, with each opening numbered, lets the homeowner see which are closed and which are waiting for access. The list is updated at each visit.

How to check the work

Each closure is checked by eye, by a light test where it can be reached, and by a check for chew marks at its edge. A closure that has been opened again is repaired with a stronger fixing and recorded.

The check after a storm is the one most often needed, because a storm can lift a fixing or open a joint. The homeowner walks the outside after each heavy storm and notes any closure that looks loose.

A chew mark on a closure is a sign that the animal has tested the edge. The report records it and the repair, so the history of the route is kept.

What the homeowner can keep up

Keep the vents and screens intact, keep the garage door seal in good repair, keep the trees trimmed back from the roof, and keep the feed and the compost away from the walls.

A monthly walk with a torch takes less than fifteen minutes and finds most of the changes that matter. The homeowner notes any new gap, any torn screen and any new chew mark, with the date.

The trees near the roof are cut back by a qualified tree service, and the homeowner keeps the branch clear of the roof edge between cuts. The feed is kept in a sealed bin, and the compost is kept away from the wall.

Closing the eaves and the roof line on a Fremont house

The eaves and the roof line are the roof rat’s route, and they are closed with metal at the vents and the soffit joints. The work is done from a stable position, and the report records each closure by its side of the house.

A soffit that has a gap at a joint is closed with a sheet of metal fixed to the framing behind the board. The metal is cut to cover the gap with a margin on each side. The joint is then sealed at its edges, so no line of entry remains between the metal and the soffit.

A gable vent with a bent screen is repaired by replacing the mesh. The mesh is fixed to the frame, not held in place by the vent cover alone. The report records the vent by its side and position.

A tree branch that touches the roof is recorded, and the report recommends that a qualified tree service cut it back. Until it is cut, the eave beneath the contact is checked more often.

Closing the ground level on a Fremont house

At ground level, the rim joist, the weep holes, the utility penetrations and the garage door are closed with metal. The gap under a shed or a gate is closed with a strip fixed to the base.

The rim joist is checked from inside the crawl space or the basement where possible. A gap at the joint between the joist and the foundation is closed with metal fixed to the sill and sealed at the edges.

Weep holes in a brick veneer are covered with mesh that lets water drain and keeps the rat out. A cable or a pipe that passes through the wall is fitted with a collar of metal, and the gap around it is filled with foam behind the collar.

The garage door seal is replaced where it is worn, and the threshold is checked for a gap. A strip of metal or a rubber seal fitted to the threshold closes the gap, and the report notes the position.

What to do when an entry cannot be reached

Some entries cannot be reached safely: a gap high on a wall, a space behind a fixed cabinet, or a gap under a deck that is built too low to enter. The report records each one as not reached, and the homeowner decides how to make it accessible.

A gap behind a fixed cabinet can be closed only when the cabinet is moved. The report recommends the move and the closure, and the homeowner decides with the cabinet’s owner or installer.

A gap under a low deck can be closed from the side, by fitting a metal skirt or a strip along the edge of the deck. Where that is not possible, the deck is noted as an open route, and the monitoring period covers it.

Materials that have failed in practice

Foam alone, thin plastic mesh, wood filler and a single screw in a soft board have all failed on Fremont houses. A rat chews through each of them, and the report records the failure when it is found.

Thin plastic mesh is gnawed within a short time. A metal mesh of a suitable gauge, fixed at its edges, is the material that holds. The report names the gauge used, so a later repair can match it.

A single screw into a soft board pulls out under load and leaves a gap. The fixing is made into sound material, with more than one screw, and the board is replaced where it is soft.

Why the order of the closures is written down

The closures are written in order so the homeowner and any later technician can see which were made first and why. A written order also shows which closures were waiting for access, and that is useful when the work is done over several visits.

A list that numbers each opening and gives its side of the house, its material and its status is the working document. It is kept in the house file and updated after each visit.

When a closure fails and is repaired, the list records the repair against the number. The history of each opening is then visible, and a repeated failure at the same opening shows the route is still in use.