Homes & villas - UK

How does Homes & villas - UK work, step by step?

1. 1

   Step 1: Survey the openings as built, not as drawn

   Every opening is measured on site before the order goes out, because openings built in blockwork or timber frame move around within their tolerances and a schedule taken off the drawings will not match what is standing. The survey records width, height, squareness, plumb of the reveals, the position and condition of the cavity closer or the frame sheathing, cill level and any deviation between one opening and the next on the same elevation. Discrepancies are resolved before manufacture - either the opening is corrected or the unit is made to suit. On a typical house that is an hour of work; skipping it commonly costs weeks, because manufactured units are made to order and a wrong size is not adjusted, it is remade.

2. 2

   Step 2: Agree the schedule, the glazing and the ventilation

   The schedule of openings pulls together every unit on the project: size, opening configuration, handing, glass specification, restrictors where the design calls for them, ventilator provision, ironmongery and finish. The designer sets what each unit has to achieve and the specification records it; the installer builds to that schedule and does not substitute. Because glass and ventilator provision are made into the unit at the factory, this is the last comfortable point at which they can change. On most projects the schedule is signed off by the design team and the client before manufacture starts, and every later change is treated as a variation with its own lead time.

3. 3

   Step 3: Check the opening and prepare the interfaces

   Before a unit goes near an opening the interfaces are made ready. Cavity closers are checked for continuity at jambs and head, the damp proof course is confirmed present and correctly lapped, the cill or sub-cill is checked for level and for the fall the detail requires, and the reveal is cleaned back so a sealant will bond to it. Any packing shims are positioned in advance at the points the frame will be fixed. On timber frame the breather membrane is dressed and taped to the opening as the detail shows. This is also the point at which anything wrong with the opening gets raised, because once the frame is in, the interface behind it is buried.

4. 4

   Step 4: Set the frame, level and square

   The frame is offered into the opening and packed at the fixing points until it is level, plumb, square across the diagonals and set to the depth in the wall that the detail requires. Depth matters more than people expect - it positions the frame relative to the weathertight line and the cavity closer, and a frame set too far in or too far out breaks that relationship whatever is done afterwards. Packers go where the fixings go so the frame is supported and not bridged, and they stay in permanently. A frame that is racked to fit a distorted opening will never operate properly no matter how well it is sealed, so a badly out of tolerance opening is corrected rather than accommodated.

5. 5

   Step 5: Fix the frame back to the structure

   Fixings pass through the frame into something that will hold them - the blockwork of the reveal, the cavity closer where it is designed to take a fixing, or the studwork and sheathing of a timber frame. The type, size and spacing of the fixings come from the designer and the manufacturer for that unit in that substrate, and they are recorded in the specification rather than decided at the opening. Timber frame introduces a further consideration the installer has to work with: the frame is designed to move as it dries and settles, so the fixing arrangement and the head detail have to allow that movement without loading the unit. The installer checks the frame is still square after fixing, because tightening fixings against unsupported packing pulls a frame out of true.

6. 6

   Step 6: Seal the perimeter - the part that actually stops water

   The perimeter seal is what keeps the house dry, and it is normally built in layers rather than as a single bead: an insulating fill in the gap between frame and structure, an air seal on the inside face, and a weather seal on the outside that is designed to shed water and to accommodate the movement between frame and wall. Surfaces are dry and clean before anything is applied, backing material is used where the detail calls for it so the sealant can move properly, and the weather conditions are within what the product allows. Sealant applied over dust, over frost, or into a joint too narrow to flex will fail in the first year, and it will fail invisibly until it appears as damp on an internal reveal.

7. 7

   Step 7: Finish the cill, the reveals and the ironmongery

   Externally the cill is completed with the fall and the end stops the detail shows, so water is thrown clear of the wall below rather than run back into it. Internally the reveals and head are made good against the frame. Ironmongery is fitted, opening lights are adjusted so they close evenly onto the seals all round, restrictors and locks are set where the schedule calls for them, and drainage slots are checked clear. Every unit is operated through its full range before it is signed off, because a unit that binds is either racked or badly adjusted, and both are far cheaper to correct before the scaffold comes down.

8. 8

   Step 8: Protect, test and hand over

   Installed units are protected for the rest of the build - the film and boarding stay on, because glass and frames get damaged by following trades far more often than by installation. Where the project calls for it, sample openings or completed elevations are checked against the requirements the designer set, and any air leakage or water testing is carried out at the stage the specification says. Records are assembled: the schedule as installed, the fixing and sealing details used, any variations, and the operating and maintenance information for the units. Handover includes showing the occupier how the ventilators and restrictors work, because a ventilator taped shut by a new owner defeats the ventilation strategy the designer built the house around.