Installing the Window and Door Frames

At stages over the last week or so, the various new window and door frames have been fitted. There is a large new French door with side lights at the rear of the new extension and a window to the new bedroom above. There are also two newly created windows in the original part of the building – one for the upstairs room and one at the side of the old part of the room downstairs which will bring more daylight into the kitchen area. Additionally, there is a rooflight in the roof section along the side of the new extension bringing in more daylight.

The large opening left in the downstairs rear wall of the extension has a lintel set in the brickwork above the opening which supports the load from above. Preformed cavity closers are fixed on either side of the opening. As the name suggests, these close the gap between the two skins of the cavity wall whilst maintaining the thermal insulation. They also have a built in damp proof course ensuring that there is an effective barrier to damp between the frame and the outer leaf of the wall. The new frame for this opening has been manufactured off site and arrives as one large unit ready for installation. The doors and double glazed panels are kept separate and will be fitted later. The builders lift the unit into position – as you can imagine, this is fairly heavy and, due to its size, not the easiest of items to manhandle. Custom joinery like this has to be manufactured to precise dimensions ensuring that there will be no nasty surprises when it comes to installation. When it’s lifted into position, you can readily see that it will fit like a glove. The builders adjust the alignment of the frame so that it’s perfectly upright and straight with the line of the wall.

Timber wedges are used between the brickwork and the frame to maintain this alignment while fixing points are made. These are drilled through the frame and into the brickwork and frame fixings driven in to secure the frame.

The new frame for the upstairs bedroom window comprises three vertical sliding sash sections. This has been carefully designed to blend in well with the original style of windows. Cavity closers are again used to seal the open end of the cavity brick work and the builders lift the custom frame into position. As you might have come to expect with this team, the unit once again fits like a glove.

The unit is aligned carefully and wedged in position so that it is vertical and straight. As with the frame downstairs, this one is also fixed in position with frame fixings. Once secured, expanding foam is used to seal the gap between it and the brickwork. This is left to cure and will be trimmed back later leaving a perfectly sealed detail. The sliding sashes with double glazed units are stored out of the way for now and will be fitted later.

A few days ago, we saw the new opening in the side wall downstairs being knocked through and a new concrete lintel being set at the top to take the load from the wall above. A new frame is now ready to be fitted here as well. The walls here are much older and are solid 9” brickwork. This means that, unlike the frames mentioned earlier, there is no cavity to be closed. There is therefore no requirement to fit vertical a dpc to the sides or jambs as they are known. The purpose of the vertical dpc mentioned previously was to prevent passage of moisture from the outer leaf of the cavity wall to the inner leaf. Here, that detail doesn’t exist. The frame is aligned and levelled then wedged with off cuts of timber before securing to the brick work with frame fixings. The small gap around the perimeter of the frame is filled with expanding foam. This is great stuff – delivered from an aerosol can, the foam expands quickly on exposure to air and fills the small voids around the edge of the frame. This is also a sliding sash window and, as with the one upstairs, the sashes themselves are stored away carefully to prevent them becoming damaged – they will be fitted later. However, the sliding sash mechanisms are somewhat more advanced than the original type. Older sliding sashes would have weights on cords mounted in the sides of the frame to counterbalance the weight of the window allowing them to easily be slid up and down. Modern designs now use sprung spiral sash balances which are pre tensioned to allow smooth lightweight operation.

The original back bedroom of the house has had a corridor sliced off it to give access to the upstairs room of the extension. It has also, therefore lost its original window in the back wall of the house so a new opening is formed in the side wall. You may remember seeing the lintel for this window being installed a couple of weeks back. The opening for the window is now knocked through. An angle grinder is used to cut through the outer part of the brick work around the perimeter of the new opening. This ensures that the edges of the opening will be clean and accurate and that only minimal making good will be required. The brick work is then knocked through to form the opening and the new frame is offered up. As with downstairs, this is a solid brick wall and the frame is simply lifted into the opening, carefully aligned, fixed with frame fixings, and expanding foam used to seal the perimeter.

In the small section of roof which returns from the rear of the new extension at first floor level, the joists have been fixed to allow the installation of a rooflight. The opening has been trimmed top and bottom with cross members. The window comes as a complete kit and installation of these is relatively straightforward. The outer frame is lifted into position in the opening and secured to the timber framework via fixing lugs on the corners and brackets mid way down each side. With this in place, the window unit is mounted in the frame. A special flashing kit is supplied separately to the window itself. The reason these are supplied separately is that different kits are available depending on the roof type and covering – in this case a slate roof. The kit comprises a flashing ‘apron’ which sits between the frame and the roof under the slates. Additional preformed flashing sections are then mounted over this rendering the whole unit watertight. The inner side of the opening is then lined with timber sections supplied as part of the kit.

If you live in the Hertfordshire area and are looking for a professional building contractor, you can get in touch with G L Smith and Sons via their website: http://www.glsmithandsons.co.uk/