It’s a fine old mess. . . bricks&mortar
Fifteen years ago, I built the house we still live in and put in hardwood windows with 4mm glass and 16mm air space. More than half of the 160 units have now broken down. I am told that if doubleglazed units are in contact with putty, the oil within the putty reacts with the seals. Removing the hardwood beads and fitting replacement units is going to make quite a mess and, if I have to do the same again in 15 years’ time, it outweighs the benefits. Are there some double-glazed units I could fit which will not break down? David Snell writes: Double-glazed sealed units set in timber frames are notoriously unreliable and do tend to break down quite easily. The trouble is that with a timber frame, the rebates cannot be very deep and there is not the room for expansion and contraction that there is with uPVC. Water tends to collect in the rebate and this reacts with and breaks down the polysulphide adhesive that glues the two sheets of glass to the aluminium spacer.
They should never have been set in putty. At the very least, 15 years ago, the recommendation would have been to use a non-setting mastic and to use spacers to lift the units away from the frame and spread the load. If you are not going to replace the frames, re-set the new glazing units on spacers and use a glazing tape. Is hydrofluoric acid the best way to improve the look of the brick that was used to construct many Victorian houses in our northern cities? DS: Hydrofluoric acid is ideal for the removal of dirt and grime and should not really harm the bricks. The problem is that it is not very nice to use because it is quite a nasty acid, which is why many firms have stopped stocking it.
If you do use it, you’ll have to be very careful not to overclean the bricks, as, with a Victorian house, it would not look right if the bricks looked brand new. Be careful not to leave it on too long. Dilute the acid, work in small areas and wash it down thoroughly with a pressure hose. Work from top to bottom so that you do not spoil what you’ve already cleaned. Thoroughly mask up any windows or other features, as the acid will etch these. You could use an alkali-based cleaner but it won’t be as quick and easy so, all in all, I think you’re doing the right thing. David Snell is contributing editor to ‘Homebuilding & Renovating’ magazine and author of ‘Building Your Own Home’, available at £ 23 plus p& p from 0870 155 7222.