Keeping the mice out

[monday]

My first time on this forum but have been lurking in the background for some time.

A simple query to start I hope: during the rewire of a new kitchen last year, the electricians made some access holes from the integral garage into a pipe duct. They have fairly substantial bundles of cables running through them but plenty of free space also. During the recent cold spell, field mice have moved in to the roof (not the first time) and it appears that on this occasion the cable access is the entry point.

The pest control company suggests that I can use expanding foam to fill the holes up. Is this OK? Will the foam affect the PVC insulation on the cabling. Is it going to be a nuisance for ever after when trying to access the cables? Given that these particular mice can apparently enter through a hole the diameter of a pencil, I can't think of any other way of doing it.

 

[EngStudent]

That is the most ridiculous 'advice' I've heard in a long time.

Expanding foam reacts with the PVC, eventually making the PVC brittle.

Silicone would be a better option but it's horrible stuff and for the extent you need it it'd be an absolute mess.

Get the sparkys back thatt installed it. How big is this hole by the way?

 

[andrew1210]

chicken wire mesh with steel wool weaved in the holes worked well when we had the little bu##ers. for some reason they left lol

edit: 100th post

 

[PrenticeBoyofDerry]

What material is the area made of, where the hole has been made?

 

[ban-all-sheds]

Expanding foam reacts with the PVC, eventually making the PVC brittle.

Polystyrene does, but expanding foam is polyurethane or polyisocyanate, I believe.

Check with the makers, but I don't think that PVC plasticiser leaching is a problem.

 

[1john]

It's PU, it's ok, the only issue would be thermally insulating a collection of bunched cables.

 

[Chri5]

Pad the hole with some rockwool and then provide a 1cm skin of mortar mix.

Strong enough to keep rodents out, but not so strong that the mortar couldn't be broken to allow future accesss.

It could be argued that the sparks should have provided such a barrier to prevent fire spread.

 

[mikhailfaradayski]

from the outside of the hole, leave a trail of small crumbs of cheese going towards the neighbours house

 

[ricicle]

from the outside of the hole, leave a trail of small crumbs of cheese going towards the neighbours house

In my experience mice actually prefer chocolate !

 

[bernardgreen]

In my experience mice actually prefer chocolate !

That apparently is true.

Some expanding foam does affect PVC insulation.

Provided the material used is only an inch or less thick ( i.e less tnan an inch length of cable is affected ) then thermal derating of the cable due to insulation need not be applied as "extra" heat will dissapated along the cable where there is no insulation.

 

[MrTinker]

In my experience mice actually prefer chocolate !

I discovered that the little blighters go bonkers for plain flower

I would be inclined to make a plug out of 1/2" plywood(or similar) and secure it in place with a bead of sealer.

 

[monday]

Thanks to all for responses. Answers to a few questions:

What material? the holes are cut through a double thickness of plaster board into a pipe duct. The duct is vertical and is between the garage and the kitchen (also connects to the roof, hence become a sort of mouse M25). The double thickness is, I believe to, create fire insulation (30 mins?) between the garage and the house.

How big? about 6" x 4" with the cable bundle about 2" dia. Seems excessive but they probably needed working space to pull cables across the duct. I have blocked the bulk of it with it a 9mm marine ply plate but can't cut it accurately enough to the cables to keep the mice out.

Fire spread? yes as above, it is a fire barrier and the electricians should probably have filled it in, or at least told the builders so that they could fill it in. Perhaps they did. So, following up on Chri5's suggestion, maybe rockwool packing with a skin of intumescent mastic might be the best option?

Mouse diet? well they seem to like whatever the pest control guy put on the table. After a noisy night moving their furniture out, they seem to have gone. Just need to keep them out.

 

[RF Lighting]

I have a 4" undergruond duct between the garage and the house, which mice were using to sneak into my house.

I tried bunging it up with rockwool, and subsequently expanding foam, both of which a mouse sized hole quickly appeared in.

Since then I pushed a scrunched up piece of polythene into the duct and then coevered the top with about 20mm of sand and cement.

I've had no trouble since.

 

[ban-all-sheds]

What material? the holes are cut through a double thickness of plaster board into a pipe duct. The duct is vertical and is between the garage and the kitchen (also connects to the roof, hence become a sort of mouse M25).

And a fire & smoke M25.

The people who did that to your ceiling are so ignorant and dangerous that it beggars belief.

The double thickness is, I believe to, create fire insulation (30 mins?) between the garage and the house.

No - a single layer gives you 30 minutes - pretty sure you need more if there's a room over a garage.

Fire spread? yes as above, it is a fire barrier and the electricians should probably have filled it in, or at least told the builders so that they could fill it in. Perhaps they did. So, following up on Chri5's suggestion, maybe rockwool packing with a skin of intumescent mastic might be the best option?

Not sure if rockwool will be a barrier to smoke & fumes...

Manufacturers of intumescent cable ducts will give you all the info you need about fire resistance etc, so augment something like that with a physical mouse barrier.

 

[PrenticeBoyofDerry]

Plaster patch it, joint repair tape and completely fill the hole in, with some universal one coat, that should sort that out and also still offer you your 30 min fire barrier.