Catflap for patio door

I did this twice, a doggie flap, once on a wooden door and once on a PVC door, knocked a hole it in based on the template on the box. Fairly easy. For glass though might be a different story

If you're talking about a laminated glass patio door this is impossible, unless you replace the entire glazed panel with a new panel made to order.

WIth our older single-glazed door with sidelight, we had the glass in the sidelight replaced with a single-glazed pane with a hole in it. The guy who cut the glass for us was someone whose name we pulled out of the Golden Pages. He was sceptical that it would work, but he gave it a go and it worked out fine. He needed the dimensions of the glass pane, the diameter of the hole required for the cat flap, the position of the hole relative to the bottom of the glass, and he then cut the glass before he called to the house.

When we had our windows and door replaced, we asked several companies whether they could provide a fixed double-glazed unit with the appropriate hole in it. Some of them immediately said no, one of them even started a row with me and told me to forget about a cat flap (needless to say, we didn't use his company), but the company we went with were able to do it and it has been great. Mind you, they never gave us a breakdown of the cost of making that glazed unit (it was made in the factory in Denmark where the windows were made) so we don't know how much it added to the cost. I also don't know whether they would have considered doing this unless we had been buying a full set of windows from them. Further still, if you are looking for this in a moving patio door, that may raise some issues too.

One option to consider is replacing the entire section of glass with a wooden/pvc/whatever piece, and make the hole in that. If it is a large area, maybe you could have the door adapted so that the portion that takes the catflap is partitioned off from the rest of the door so that the catflap area is non-glass and the rest is glass. Yet another option is to put the cat flap through a wall - there are flaps available that are designed for this, but you would want a reliable builder to do this for you if you are to avoid letting dampness into the house.

One other thing to bear in mind: we opted for windows with a very good U-value for a high level of insulation, but the area immediately around the catflap is one of the main places where condensation appears. It makes sense that the presence of the catflap reduces the insulation in that area, but I often wonder whether it has a bigger (negative) impact than I had anticipated (not helped by the fact that the catflap is in a door set into a north-facing wall though).

Thanks everyone. I'm the friend, by the way! I'm happy to get a custom made double glazed unit if I can find someone reliable and at the right price. No-one I've spoken to so far is willing to do the job, but I'll keep trying anyway. If not, I guess I'll look into replacing all or part of the door with PVC.

If anyone has any more thoughts on the subject - keep 'em coming!

Well I wondered what sort of cat flap you were thinking of fitting? We had cat flaps in two previous houses and other cats in the neighbourhood were coming in. You can buy the type that locks shut but then that defeats the purpose. The flap lets in a lot of draughts and several times our cats came flying through and brought the whole lot with them leaving just the hole in the door where the flap was. There is another type that is operated by the cat collar which has a magnet and is only supposed to let in the resident cat. We have never had much success with cat flaps however well they are fitted. I would never put a cat flap in a double glazed door knowing the problems which we have had before. Now pussycat goes out and stays out until let in as she can always go to the shed which is left open slightly. All in all I dont think cat flaps are worth the trouble and look unsightly.

The company that we used are [broken link removed]. I would be surprised if they were able/willing to do just the glazed unit, and at a reasonable price for such a once-off, but they may be worth getting a quote from.