Know this isn't 'green' but I'd appreciate some advice, please, as I've searched the web and have not found any info elsewhere. I've just started fitting softwood window frames into new apertures in an extension (after the builder cleared off with my money). The windows are top hinged and have a slider mechanism down the insides of the frame. There's a 3" gap at the bottom of the mechanism which would take a fixing point. Trouble is, there's no room at the top to fix the frame to the blockwork. I've used frame fixings before, without much success - some seem to jam, bend or break or just go wrong, even after using the correct drill and clearing the dust from the hole, so I'm not confident about using them anyway. (And do you drill the pins in or hammer them??) Would it be okay to use some sort of bracket to hold the windows in place where I can't fit a conventional fixing, perhaps using simple 'L' shaped ones which would be hidden behind the plasterboard eventually? Thanks for any comments.

You can get various fixings that go directly into concrete blocks. Wedge the frame in the correct place, drill pilot hole through frame into block, screw in fixings. Be careful to get the concrete (fine thread) and not aereated block fixings ( coarse thread). The other way, I have seen it done for windows and a wooden door frame, it to wedge frame in hole, squirt in special foam, leave 1/2 Hr then trim of excess with sharp knife and point/ plaster a fillet in place. Seems to work but for how long?
Frank

Many thanks for all those ideas! I've discovered two big apertures are 1830mm wide when the frames are 18000mm, due to the crooked builder also being illiterate (he also built one side wall 50mm higher than the other and made the door aperture far too small). I suppose some wooden strips down each side of the window will fix it, though.. Thanks again, guys.
Tony, the walls are conventional cavity walls in 4" concrete blocks. I thought frame fixings didn't use plugs but had those plastic sleeves (same thing..?) Ed.

They sound interesting. No need to use wood as a packer in the first one, I've just cream-crackered myself trying to grind down the blocks as the aperture was too small and not square - after three attempts I'm almost there, but dripping. It was quicker and cheaper than buying a planer! If I shouldn't use wood as a packer on those frames which are 30mm too small, what would I use? I intended to use a couple of pieces of planed timber screwed/glued to the outside of the frame and treated to match. I guess the rendering will just about cover it..