We replace worn or broken letterboxes and fit new ones in uPVC and composite doors, and fit cat flaps into uPVC door panels or into new double glazed units made with a hole for the flap. How it is done depends on what the flap or letterbox is going into: a uPVC infill panel can usually be cut on site, while glass has to be made with the opening already in it, because toughened glass cannot be cut once it has been toughened.
Letterbox replacement and fitting
A letterbox gets used every day and sits in the most exposed part of the house. Over the years the spring weakens so the flap rattles or will not close, the outer plate fades or cracks, the internal flap breaks off and cold air streams through. On uPVC doors the letterbox usually goes through the infill panel, while on composite doors it passes through the GRP skin and insulated core.
Common letterbox problems
- Flap stuck open or rattlingA weak or broken spring, or a hinge pin that has worn. Usually the answer is a new letter plate rather than a repair of the old one.
- Draughts through the doorMany older letterboxes have no internal flap or brush. A replacement with an internal flap or brush seal cuts draughts noticeably.
- Cracked or faded plateCheap plastic plates crack and fade in the sun. A replacement in a finish that suits the door freshens it up.
- Letterbox in the wrong placeSometimes a letterbox needs to move, for example when a door is fitted with a new panel. Our uPVC door panel replacement page explains how panels are made with or without a letterbox opening.
Letterbox security
A letterbox is a known weak spot: a thief can use a tool through the opening to reach keys left near the door or to operate the inside handle. Simple steps help. Keep keys well away from the front door, and consider a letterbox guard or cage on the inside, or a letter plate with a built-in baffle. A door with a lever handle that can open from the inside without a key is more at risk, which is something to keep in mind alongside lock security. Our anti-snap lock upgrade page covers the cylinder side of door security.
Cat flap fitting
The right way to fit a cat flap depends entirely on the door or window it is going into. We can explain the options before anything is ordered.
| Fitting into | How it is done | Things to know |
|---|---|---|
| uPVC door infill panel | We cut the opening on site and fit the flap with the correct liner or tunnel for the panel thickness. | Usually the simplest option. If the panel is in poor condition, a new panel with the flap can be better. |
| Double glazed unit in a door or window | A new sealed unit is made with a round hole already in it, then the flap is fitted at the second visit. | Toughened glass cannot be cut after toughening, so the existing glass cannot be cut on site. |
| Composite door | Depends on the door and maker. Some can be cut, others are not designed for it. | Check the door’s guarantee paperwork first; cutting the slab may affect it. |
Cat flaps in glass
A cat flap in glass is a popular choice for back doors and lower windows, because it avoids cutting into a door panel and keeps the door looking tidy. The existing unit is removed and replaced with a new sealed unit made to measure with a hole in the right position. In a door, or within 800 mm of the floor, that unit must be safety glass, so it will be toughened or laminated. The cat flap is fitted through the hole with an adaptor suited to the overall thickness of the unit. This uses the same process as our glass replacement work, so the old unit is measured at the first visit and the new one fitted at the second.
Choosing a flap
Many people now choose a microchip cat flap so only their own cat can come in. These are usually larger than a basic flap and need a mounting adaptor for glass or thick panels. Tell us the make and model you want, or ask us before you buy, so we can check it suits the door or glass. Position matters too: the flap needs to be at the right height for the cat on both sides, which can be different if there is a step outside.
How a letterbox or cat flap job works
- We call you back. We ask what you need, which door or window it is, whether it is uPVC, composite or aluminium, and whether there is glass involved.
- Photos. A photo of the door from inside and out, and of any existing letterbox, helps us plan the work.
- Visit and measure. We check the panel or glass, the thickness and the best position, and confirm the parts.
- Written quote. We explain the options, including whether the panel or glass needs replacing, and give a written quote.
- Fitting. A letterbox in a uPVC panel can often be fitted at the first visit if the part is carried. Cat flaps in glass need the new unit made first.
- Checks. We check the flap opens and closes freely and that the door still opens, closes and locks properly.
Around Liverpool and Merseyside
Most of the front and back doors we see on inter-war and post-war semis are uPVC replacements fitted from the 1980s onwards, often with letterboxes that have now done decades of service. That is common in places such as Norris Green and Huyton. Newer estates around St Helens and elsewhere have more composite doors, where checking the maker’s guidance before cutting matters. We take on this work as part of our double glazing repair in Liverpool and across the region.
What affects the cost?
A replacement letterbox in an existing opening is a small job. Cutting a new opening, adding a letterbox guard or fitting a cat flap through a uPVC panel takes more time. A cat flap in glass involves a new made-to-measure sealed unit, so the unit size, glass type and any obscure glass are the main factors. We quote once we know the door, the glass and the flap.
Need a new letterbox or a cat flap fitted?
Call 07777 659786 or leave your details with the door type, whether it is going into glass or a panel, and the flap you have in mind. We will call you back and arrange a visit with our Merseyside window and door repair team.
Frequently asked questions
Can you fit a cat flap in double glazing?
Yes, but not by cutting your existing glass. Toughened glass cannot be cut after it has been toughened, so we measure the opening and have a new sealed unit made with a hole for the flap. It will be safety glass if it sits in a door or low down. The flap is then fitted with a suitable adaptor.
Can a cat flap be fitted into a uPVC door?
Usually, yes. If the lower part of the door is a uPVC infill panel, we can cut the opening on site and fit the flap with the right liner for the panel thickness. If the panel is old or damaged, a new panel with the flap fitted can be the tidier option.
Can you fit a cat flap in a composite door?
Sometimes. Composite doors have a GRP skin over an insulated core, and some makers do not support cutting into the slab. Check your door’s paperwork first, as cutting it may affect the guarantee. We can advise on alternatives, such as fitting the flap in a glazed panel next to the door.
How do I stop draughts coming through my letterbox?
Replacing an old letter plate with one that has an internal flap or brush seal usually makes a clear difference. If the letterbox is in good condition, an internal draught excluder may be enough. We can look at the door as a whole, as draughts can also come from worn door seals.
Is a letterbox a security risk?
It can be. Thieves sometimes reach through a letterbox for keys left near the door, or try to operate the inside handle. Keep keys away from the door and consider a letterbox guard or a plate with a baffle. These simple measures make the letterbox much harder to misuse.
Can you move a letterbox to a different position on the door?
On a uPVC door, the simplest way is often to replace the infill panel with a new one made with the letterbox where you want it, rather than patching the old opening. On a composite door, options depend on the door. We will explain what is practical after seeing it.