Composite Doors Advice and Questions Answered
Will the door frame be replaced ?

In most circumstances all of the old door frame, threshold, and cill, must be removed whether they’re timber, aluminium, or UPVC.

The new door comes pre-hung in its new UPVC frame ready for installation.

What Frame options are available ?

The standard UPVC outer frame is approx 70mm x 70mm with a chamfered or bevelled decorative detailĀ  or an ovolo or sculptured decorative detail.

Frames sizes and shape do vary between suppliers but all are very similar to Door-Stop’s options shown in cross section below.

Outer Frames Detail

If your brickwork opening is narrow (885mm or less in width) then Croydon Doors recommend a slimmer outer frame to maintain as much passable width as possible and ensure you can choose from the widest range of styles available.

Door openings less than 835mm wide are limited to those designs with smaller centrally located glazing.


Will the frame be draightproof ?

The new frame will incorporate an external rubber (or neoprene) gasket to prevent water ingress.

Inside the frame will be one or more brush-strips to reduce draughts and prevent heat loss.

The energy rating of your new door will vary depending on manufacturer, design, and options chosen, but all new composite doors will be a significant improvement on any older timber, UPVC, or aluminium doors.

What about borrowed lights and sidelights ?

When removing your old door frame you will most likely have to replace any windows or fixed panes of glass above or either side of the door.

Using Croydon Doors Door-Designer you can select from a list of different fixed top lights and sidelights when designing and pricing your new front door.

Small top lights can be a welded addition to the new door frame whereas sidelights will be a separate frame that we couple together on site.

Top lights will be fitted with a new double glazed unit in a glass pattern of your choice; we are also able to supply and fit numerals using bespoke etch effect film from Purlfrost.

Sidelights can also be fitted with a double glazed unit in a glass pattern of your choice. If size allows (450mm wide or greater) we can supply and fit a composite side panel in matching style and colour to your new front door.

Ask your surveyor on site for more Composite Doors Advice on sidelights, toplights, minimum and maximum sizes, and glazing safety regulations.



What Threshold options are available ?

At Croydon Doors we recommend a Low Aluminium threshold whenever possible as pictured below.

Aluminium Threshold

The aluminium thresholds typically come in white, silver, or gold as standard, some other colour options are available.

Tall UPVC welded thresholds draw attention to the UPVC frame and look less like traditional timber door as well as being a potential trip hazard. Care must be taken when measuring the internal floor level to make sure the new door has plenty of clearance. See links to cill options.

What Cill options are available ?

Normally a 30mm x 150mm drop nose UPVC cill is supplied as standard but other sizes include 85mm, 180mm, and 225mm.

If your internal floor level is much higher than outside then we might specify a “Radlington” cill. The Radlington UPVC cill is taller (55mm) and helps resolve any internal floor level problems. Sometimes when removing a heavy hardwood timber cill it is better to fit the stronger Heritage cill to help support the aluminium threshold and prevent deflection from people standing on the threshold.

If you have a stone or tiled cill then we can fit the aluminium threshold directly to that or we can fit a 30mm x 150mm bull nose cill which will fit flat onto the masonry below.



How is a standard composite door made ?

At Croydon Doors we would describe a standard composite door as being a framed reinforced slab with rigid foam core and GRP skin.

Our most popular door is from Door-Stop’s standard range of composite doors which are secure, thermally efficient, and competitively priced.

It can be difficult to get unbiased Composite Doors Advice and solid core doors are being heavily promoted by the respective manufacturers so I would suggest examining all the products we have on offer at Croydon Doors and forming your own educated opinion.

What is a solid core composite door ?

Solid core doors are made up of engineered timber with a GRP skin.

Solid Core Make Up

Solid core leafs are thicker at 48mm (compared to 44mm), are perceived as more rigid, and perhaps more resistant to a sustained attack with cutting tools.

Because they are more rigid they can also accommodate a larger glass area and so you find some designs in solid core that you dont get in standard composite.

Click to see Solidor Video showing how they are made.


How is Rockdoor different from other composites ?

Rockdoor slabs are made to measure with a carbon fibre reinforced frame and rigid foam core and are 50mm thick compared to 44mm for standard composites.

Rockdoors are also permanently glazed compared to cassette glazed so the glass can never be removed and doesnt have the raised moulding that come with standard and solid core composites.

Because Rockdoor slabs are made to measure they come in larger sizes than most other composites so if you have a taller door opening (2150-2250mm) the new door and frame can be made to fit without the use of large thresholds or add-ons.

Rockdoor also have some unique styles and glass options and are visibly different from all other types of composite door.

For a Contemporary or modern style of door the Rockdoor range looks more sleek and minimal because of the lack of raised glazing cassettes. Choose a modern design from the Rockdoor Ultimate range with a long pull handle and slam lock for a fantastic looking door.

Click to see Rockdoor Video showing how they are made.

What are the Energy Ratings ?

All omposite doors have much improved thermal efficiency compared to older doors of all type.

Energy ratings vary depending on the style of door and area of glazing usually ranging from A+ to D and every door fitted with have its own energy rating certificate.

Can the glass be changed ?

Door-Stop, Solidors, Endurance, Hurst Plastics, and generally most types of composite doors, are all “cassette” glazed which means an external and internal raised bead or moulding retains the double glazed unit in place.

Cassette glazed doors can have the glass removed and replaced although it sometimes might require a new “cassette”.


Rockdoors are manufactured differently and factory assembled around the glass so it cannot be replaced.

If you need to change the glass we would strongly recommend on site composite doors advice from a glazier with appropriate experience.


What is safety glazing ?

Building regulations require that glass fitted in or close to a door confirms to safety testing.

Safety glass protects against injury due to impact.

Toughened glass is treated to shatter into very small pieces when broken.

Laminate glass has a thin plastic film between two sheets of glass and this keeps the glass intact where it to be broken.


Which glass is more secure ?

Although toughened glass is hard to break it does shatter into very small pieces so laminate glass is better for security and a requirement to meet police Secure By Design standard.

If you are having a thumbturn cylinder installed then it would be standard Composite Doors Advice to get laminate glass.

How thick is the double glazed unit ?

The double glazed unit thickness depends on the supplier but usually 24 or 28mm (some older doors might be 20mm or 22mm).

  • A toughened double glazed unit will be 4mm glass – 16mm or 20mm spacer – 4mm glass..
  • A laminated double glazed unit will be 6.8mm laminate – 18mm spacer – 4mm toughened.
  • A triple glazed unit will be 4mm glass – 8mm spacer – 4mm glass – 8mm spacer – 4mm glass.

If you need to change the glass we would strongly recommend on site composite doors advice from a glazier with appropriate experience.



How do Lever door handles and locks work ?

Lever handles and locks are most commonly fitted to all modern front doors.

Raising the handle positions the hooks in the locked position and lowering the handle disengages the hooks from the locked position.

Turning the key engages the deadbolt and locks all the hooks in place preventing the handle from being lowered.

What is a split spindle lever handle and lock ?

A standard lever / lever handle and lock will mean the handle works the latch both from inside and from outside and would mean the door has to be locked with a key to prevent someone outside gaining entry.

A split spindle is generally required for front doors which means the latch is only worked by the key from outside and prevents anyone without a key from getting entry.

How secure is a euro cylinder ?

The locking cylinder can be key outside and key inside or key outside and thumbturn inside.

Thumbturn inside means you can lock the door at night and not have to worry about finding a key to get out.

If you are having a thumbturn cylinder installed then it would be standard Composite Doors Advice to get laminate glass.

There are many types of cylinder from many manufacturers all with varying degrees of security.

The level of security boils down to how easy the it is to pick (or bump) or how easy it is to snap.


Are composite door locks easy to use ?

Composite doors multipoint locking in conjunction with multiple gaskets and brush strips can make a new composite door feel stiff to open – close – and lock but this does ease over time.

Customers who have reduced strength in there fingers and wrist do benefit from longer lever handles and will find a working lever handle (not a split spindle) easier to use than the key.

Aluminium low thresholds are suitable for wheelchairs, trollies, and prams, and remove any potential trip hazard.

What are pull handles and slamlocks ?

Modern door furniture and locking options include pull handles and slamlocks.

Pull handles include long and short straight bars,curved bars, victorian centre knob, and simple escutcheons.

All of these pull to close handles require a slamlock.

A slamlock works when the action of closing the door triggers spring latches to engage the hooks in the locked position and remove the need for any lever type handle.

A simple escutcheon and slam lock (no lever handle outside) looks much more like a traditional timber door and the key can be positioned further up the door rather than the standard middle cylinder.

Pull handles and slam locks are more expensive than standard lever handles and locks.


Can you fit a catflap ?

It is possible to fit a catflap to some styles of composite door.

Easier if you choose a solid core door and pick a style that doesn’t have any recessed moulded panels.

Choose a cottage style door from the Door-Stop solid core range or from Solidor’s Flint range of designs.

We can supply and fit a Staywell four way locking catflap which we stock or you can supply your own but we do recommend buying a new catflap rather than trying to re-use your existing.