Fitting external roller shutters and blinds

This price-list item covers three systems. They are fitted in a similar way, but each one suits a different situation.

External roller shutters

A roller shutter has a curtain of aluminium slats that rolls up onto a shaft inside a box above the window. Standard slats are foam-filled, which damps a little noise and heat. Stronger extruded slats are solid aluminium profiles and make sense where security is part of the brief. A shutter can make a room almost completely dark, so people mostly choose it for bedrooms. The downside: once it is down, you cannot see out and very little light gets in.

External venetian blinds

An external venetian blind has separate slats that you can tilt. You can block direct sun and still let soft, diffused light into the room. The most common slats are C-shaped or Z-shaped and come in different widths. Z-slats overlap better when closed and give a darker room. Venetian blinds are more sensitive to wind and should be raised when it gets gusty. That is why motorised blinds are often supplied with a wind sensor that pulls them up automatically.

Zip screens

A zip screen is a strong fabric that rolls into a box and runs in side rails with a zip along its edges. The zip holds the fabric in the rail, so it does not flap in the wind and insects cannot get past. You can still see out through the screen, it shades well and it looks modern. Screens suit large glazed areas and patio doors. They do not give full blackout unless you choose a special blackout fabric.

Before you order, decide where the box and guide rails will sit. This affects how the facade looks, how demanding the installation is and whether you end up with a cold spot around the window.

Face-fixed on the facade

The box is fixed to the wall above the window and the rails to the wall on either side. This is the quickest option for finished houses where nobody wants to touch the insulation. The box stays visible, so you pick a shape and colour that match the windows or the render. On an externally insulated wall the fixings must go through the insulation into the masonry, using spacer brackets or special anchors made for insulated facades. A fixing held only by polystyrene will not last.

Fitted in the reveal

The box sits under the lintel and the rails are fixed into the reveals, the side walls of the window opening. The facade looks cleaner, but you lose some daylight because the box takes up part of the window height. The reveal has to be deep enough for the box and reasonably straight.

Concealed box in the insulation

The box is hidden in the insulation layer or in the lintel, and from outside you only see a narrow slot. It looks neat, but it has to be planned before the insulation goes on or before the windows are installed. The box needs its own insulation, otherwise a cold spot forms above the window. Some systems have the box built into the window frame and are installed together with the window. Retrofitting a concealed box into a finished insulated facade is rarely done, because it means cutting into the facade and repairing it afterwards.

The way you operate the shading affects everyday comfort and also what needs to be prepared in the wall.

• Strap is simple and needs little maintenance. It suits smaller shutters; with large, heavy ones pulling becomes hard work. It needs a winder on the inside wall and a pass-through in the frame or wall.
• Crank is used for both blinds and shutters. A rod passes through the wall or frame at an angle and a jointed handle hangs inside. It is reliable, but you will see it in the room.
• Motor sits inside the shaft or in the head rail of the blind. You operate it with a wall switch, a remote control or a smart home system. You can set schedules, group windows together and add sun or wind sensors. For large openings and for venetian blinds, a motor is now the usual choice.

A motor needs a power cable at the window. Electrical installation and connection to the mains must be done by a qualified electrician, and in many countries the work has to be certified. The shading fitter normally installs and sets up the motor, but connecting it to the house wiring is the electrician's job. If cables are added later, they often run in trunking or in a chase in the wall that then needs making good.

The installation itself is quick when everything is ready. Most time is lost when the crew finds out on site that something is missing.

• Accurate survey. Shading is made to measure and cannot be adjusted in the workshop afterwards. The supplier usually does the survey and then takes responsibility for the sizes.
• Cables for motors. The supply should be at the window before installation, ideally in a conduit so the cable can be replaced later.
• Access to the windows. On the ground floor a ladder is enough. Higher up, the work is done from inside through the window, from scaffolding or from a lift. On new builds and during insulation work it pays to fit the shading while the scaffold is still up.
• Space inside. Take down curtains and move plant pots and furniture away from the windows so the crew can drill and work.
• Power and storage. The fitters need a socket and a bit of space to unload boxes and rails.

External shading changes how the building looks. In a block of flats, ask the building management or owners' association for consent first. They often have rules on box colour and type so the building stays uniform. For houses as well as flats, check with your local building authority whether a change to the facade needs any approval under local building regulations. Do not assume nothing is required, especially for listed buildings and in conservation areas.

The procedure varies by type, but the basics are similar. First the fitter checks that the delivered size matches the opening and that the walls are as expected from the survey. Then they mark the position of the box and the guide rails. The rails must be plumb and parallel to each other, otherwise the curtain or fabric will rub.

Next comes drilling and fixing. The fixings depend on the wall: in solid brick or concrete a standard plug works, while hollow clay blocks or aerated concrete need anchors designed to hold in that material. On insulated walls the fixings go through the insulation into the structural wall, and the holes are sealed so water cannot run into the insulation. The fitter drills into the window frame only if the window manufacturer allows it; otherwise the profile can be damaged and the window warranty lost.

Then the box or head rail goes up and the curtain, slats or fabric are fed into the rails. For a crank or strap, the fitter makes a pass-through in the wall or frame and installs the control inside. For a motor, the cable is connected and the end positions are set, meaning where the shading stops at the top and bottom. If these are wrong, the motor either presses the curtain into the sill or pulls it too far up.

Finally the outside joints are sealed, the covers go on and the fitter runs several test cycles. A typical window usually takes one to two hours. Large patio doors, a concealed box or awkward access can take half a day. Sealants need anywhere from a few hours to a few days to cure fully, depending on the manufacturer, so avoid spraying fresh joints with a hose in the first hours.

The same price-list item can take very different amounts of time in practice. These things help:

• Ground floor or scaffolding already in place
• Solid, sound masonry without cavities
• Straight reveals and a square opening
• A cable already waiting at the window
• Several identical windows in a row, where the routine repeats

These make it harder:

• Upper floors without scaffolding, where a lift or work from the window is needed
• Thick external insulation that needs long anchors or spacer brackets
• Aerated concrete and hollow blocks that need special fixings
• Uneven reveals, where the rails have to be packed out
• Large sizes and heavy curtains that need two people
• Running cables afterwards and making good the chases
• Removing old shading first

Many faults do not show straight away, but after the first winter or the first strong wind.

• Wrong measurements. The rails do not sit properly, the box is too short or the curtain does not reach the sill. Often the only fix is a new part.
• Rails not parallel. The shutter rubs, the blind comes down crooked and the motor overheats. You notice noise and gradual wear.
• Fixings only in the insulation. The rails work loose over time and the whole system rattles in the wind.
• Unsealed holes in the insulation. Water gets behind the render, the insulation gets damp and the render can crack in frost.
• Cold spot at the box. A cold area forms above the window, moisture condenses on the inside and mould can appear.
• Cable without a conduit. If the motor fails, the cable cannot be replaced without opening the wall.
• Wrong end positions. The curtain is pushed into the sill or the slats bang into the box.

Mistakes in use are common too. It often happens that someone lowers a shutter in frosty weather while it is frozen in the rails, and the motor or slats get damaged. External venetian blinds suffer when they are left down in windy weather. Ask the fitter to show you at handover what the shading can and cannot cope with.

Leave the actual installation on the outside of the building, especially at height, and the motor connection to professionals. What you can do yourself is a preliminary survey and the preparation. It gives you a realistic idea of what is possible and makes quotes easier to compare. The supplier will still do the final survey and stand behind the sizes.

1. Measure the width of the opening from outside in at least three places: top, middle and bottom.
2. Measure the height on the left, in the middle and on the right, and write down the smallest figure.
3. Check with a spirit level whether the reveals are plumb and the lintel is level, and note any deviations.
4. Measure the reveal depth from the facade to the window frame to see whether a box would fit inside the reveal.
5. Find out whether the wall is externally insulated and estimate the insulation thickness from the reveal depth or the drawings.
6. Find out what the wall is built from, for example from the drawings or from old drill holes.
7. Sketch which side the control should be on and where the nearest socket or junction box is.
8. Photograph each window from outside and inside and send the photos to the supplier with your measurements.
9. Before installation day, clear the area around the windows and take down curtains and poles that would be in the way.

At handover, go round every window with the fitter. Have each shutter or blind raised and lowered several times, and on venetian blinds have the slats tilted too. Listen for jerky movement or rubbing. Look from outside as well to see that the rails are straight and the joints sealed.

• Size and type match the order, including the colour of the box and rails
• Guide rails are plumb, parallel and firmly fixed
• The shading runs smoothly, without rubbing or unusual noise
• The curtain or slats sit level at the bottom and disappear fully into the box at the top
• On venetian blinds the slats tilt evenly across the full width
• On zip screens the fabric stays in the zip along the full height and does not ripple
• The motor stops at the correct end positions and the switch or remote works
• Any wind or sun sensor included in the order is set up and tested
• Pass-throughs in the wall and holes in the insulation are sealed
• The windows open normally and the controls do not get in the way
• The area is clean, with no dust or leftover material
• You have the user manual, the warranty and, for motors, the electrician's certificate for the connection