Thinking about building a loft conversion? Even with two identical houses, no two lofts are ever the same and there will always be slight variations. This page contains the general building process I follow and the stages at which the building inspections are made. Obviously I have all the necessary planning permission in place and in writing (I did it on building notice, as it fell within permitted development rights) before starting, and get the scaffolding up.
There is much less mess made in your house if you cut through for the loft conversion staircase at the last possible moment when the first fix is done and all the walls in the new loft are plaster-boarded, ready to fit the stairs.
Begin the floor structure - Depending on the size of the house and design, the floor structure includes the timber and/or steel beams, purlins and purlin wall, new floor joists hung from beams on joist hangers, trimming around the stairwell with double/treble joists, noggins/bridging and sound insulation. I removed the fiber-glass insulation when I was Joisting and put it back after all the noggins went in (these need to be tight and solid to prevent squeaks and to stiffen the floor structure up). I then added 100mm rock-wool sound insulation on top of that.
Building inspection – before the flooring goes down a visit is made by the building inspector to check that you are building a loft conversion properly, to the approved plans and that the build quality meets relevant building codes.
Lay the floor once the inspector is happy with the structure and insulation, and the pipework is in place. I used 22mm moisture resistant chipboard 2400x600mm sheets.
The rest of the structure includes doubling up rafters, building any dormers (if there is a large flat roof dormer going up this may need to be built before the joisting can be finished in stage 1), ceiling collars (sometimes need to be bolted), flitch plates, purlin wall and purlin, pinch binders, (internal stud walls aren't always structural), fit door linings and trim out a loft trap if needed.
First fix electrics - the electricians can fit all the cables for lights, sockets, T.V. aerials, smoke detectors and phone lines etc. when the walls are up.
*Insulation regulations are always changing make sure you are up to date and follow the approved spec when building a loft conversion*
Other loft conversion insulation will include solid sheet/board insulation like Celotex to purlin walls(100mm) and skeelings (underside of rafters/angled ceilings - 70mm), 100mm rolls of rock wool sound or Fibre-glass heat insulation in between studs of internal walls and above ceiling collars. Multi-layer insulation like Thinsulex over rafters. This will need to be counter battened for the plasterboard as you can't screw through Tri-iso/Thinsulex, the screws just get wrapped up in wool. Some flat roof dormers need 70mm between ceiling joists and 35mm over the top, before plasterboard.
Once the loft is insulated the building inspector will make another visit to again check that the construction and insulation is to the required standards.
Plaster-boarding – Once the insulation is installed the 12.5mm plasterboard can be cut and installed. Foil backed plasterboard is used on the skeelings to prevent condensation seeping through. Use foil backed plasterboard on ceilings and bathroom walls if you're not using aqua board or marine ply where the tiles will be.
Once everything that can be done before breaking through into the main house is done, cut out the stairwell ready for the staircase to go in. You'll need a mask no matter what, but if it's a plaster and lathe ceiling it will be a seriously messy job. Vacuum as much crap off the top as possible first. The dust is black and gets everywhere, so dust sheet everything up, and seal all the doorways shut. I've even in some instances nailed a tarpaulin with battens to the wall underneath to catch everything as it's kicked down then cleared it from above. Another thing you can do is screw a tarpaulin to the ceiling with battens around the stairwell (bang nails down from above in the corners so you know exactly where to batten) and the tarp acts like a shower curtain guiding all the mess straight down onto the floor.
Trussed roofs with plasterboard ceilings are nowhere near as messy.
After you install the new loft conversion staircase, it is pretty rewarding walking up the stairs for the first time when the two levels are linked. The underside will need to be plaster-boarded and if there's a turn like in a winder flight you may need to form the curve with battens and EML mesh. I cut little bits of strapping off the strip to use like washers when fixing the mesh to the battens with 40mm plasterboard screws. If it's not tight the plasterer won't be able to finish it.
Once the staircase is in and the first fix work is all complete the plasterers can start. It really begins to look like a room/part of the house at this stage
When building a loft conversion whether a DIY project or professional job, the finishing stages are all about seamlessly tying the new loft conversion into the existing home, like in the picture above. Done properly and with matching materials and mouldings, the new loft can seem like it just 'grew there', and decorated seem like it has always been part of the house.
Put your feet up, relax and enjoy! Oh, and get all the furniture up..
Have a comment or question about building a loft conversion?