I'm planning to replace 50's steel framed windows on an 18th C cottage with timber casements. On the rear elevation these are 2300 wide and 1200 high so I have some choice over numbers of casements and glazing bars. Does anyone know of any design software that would help sketch out the options quickly?
Second question, I know there is a rule requiring toughened glass for windows with cills below 800 mm. Does that apply both sides? My outside cill is only 300 mm from ground level. (Can't easily dig it out, although I would like to, because I would have to re-lay all the drains).
The toughened glass law came out in the '80's to replace 3mm glass with 4 mm float. Most modern galss is of the required standard so don't worry about that.
An immediate fix for the most likely problem you have with that sort of window is to clean the rebates on the opening casements and stuff and coat one edge with a thin lick of engine grease, brush with a pva and meths mixture, or thick washing up liquid and immediately apply a thickish line of silicon mastic to the other meeting faces.
Don't forget to silicon all around the outer edges of the window too. All being well this should last you well into the summer. Take measurements to replace the whole lot from the outside after knocking back a little of any plaster on the reveals to get the true opening size.
If you order ready made units, check they have given you half an inch overall on the height and the width before you accept delivery. And make sure that is in the contract that they will accept immediate return of the windows if US.
When closed, the silicon will fill any draughty gaps and might squeeze out past the rebates. Scrape the excess off and leave closed until the silicon has grown hard. Use an high modulus.
These casements were fitted with a very hard bedding compound. Getting them out might be a PITA. Go easy if you wish to save the timber subframe.
If you can save that, you can get ally frames to fit it. They will look a lot better than plastic windows in an old building.
Score down the reveals if they are plastered; to stop the plaster breaking past the edges of the windows and making a patch necessary and time consuming. (And almost always impossible to match.)
If you can afford it get double glazed oak windows made and pressure treated.
Finally, replace the plaster on the reveal with a sand and cement mix. Screw or wedge a lath onto the edge, so it sticks past the reveal about an inch depending on how much cover you need. (Never less than an half inch.)
Slap the mix in with a gauging trowel and brush the exces off the window straight away. If you are using aluminium, protect that with masking tape or you will regret it.
Scape the finish level and brush the finish with a soft bristled brush. You can knock the lath off straight away if you are half competent. Then brush excess from behind that.
It could be left a day or so if you are a newbie and a trowel or wire brush used to scrape off any excess from under the lath.
Thanks for the suggestion; it looks quite neat, but there are a few general "house design" packages out there and there's not much detail of what it will do on windows. I'm hoping to find a user recommendation.
On the steel windows, previous owners did many extraordinary things which I am gradually reversing. However I could be grateful they didn't let it decay to the point where it had to be pulled down and replaced with new build. Across the road there is a terrace of assorted cottages which go back several hundred years, with sections re-faced in Georgian, Victorian, and Queen Anne. One of a pair of the latter was allowed to decay to the point of uninhabitability, and the planners allowed it to be pulled down and rebuilt as a modern fake. So now between a fine Victorian brick house and the other QA there is this monstrosity in modern brick, cavity walled in stretcher bond, with windows slimmed down to meet insulation requirements and thus only two thirds of the width (although the same height) as windows in the adjoining properties.
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