5 Mistakes to Avoid With Self-Tapping Screws in uPVC (and the Fixes)

The short answer

The five mistakes that cause most loose handles, hinges and keeps on uPVC:

Using wood screws instead of self-tapping uPVC screws
Overtightening, which strips the thread the screw has just cut
The wrong length: too short to reach the steel, or long enough to hit the glass
No pilot hole when going into the steel reinforcement
Putting the same screw back in a hole that's already stripped

Most of these cost nothing to avoid. The last one needs a repair screw.

A uPVC frame is a hollow plastic profile, usually with a steel reinforcing bar inside. A screw only holds well when it bites into that steel, or into enough plastic. Every mistake below comes down to the screw not getting a proper grip.

Screws and fixings for uPVC

Most jobs

Self-Tapping uPVC ScrewsFrom £2.99

Cuts its own thread
25, 32, 38 or 45mm
Zinc-plated, countersunk

Choose this if: you're fitting something new into sound uPVC.

Choose your length

Screw won't tighten?

uPVC Repair ScrewsFrom £2.99

Thicker, deep-cut thread
Re-uses the same hole
Hardened steel core

Choose this if: an old screw spins in its hole.

View repair screws

Best-selling fixing

Jack Nut & Machine Screw 5.0 (1 reviews) £0.60

Opens out behind the wall
Gives a metal thread
Machine screw included

Choose this if: there's nothing behind the plastic to grip.

View jack nuts

Do it by hand

STANLEY 6-Way Screwdriver£10.05

6 bits in one driver
Double-ended bits stored in the handle
Finish by hand, no stripping

Choose this if: you want to avoid overtightening with a drill.

View the screwdriver

Not sure which screw you need?

Send a photo of the fitting and the hole to info@homesecureshop.co.uk, or bring the old screw to our Aintree counter and we'll match it.

Call 0151 521 8089

4.8 from 1,000+ reviews
Same-day dispatch, order by 2pm
Trade counter in Aintree, Liverpool
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Compare uPVC fixings

Feature	Self-Tapping uPVC Screws	uPVC Repair Screws	Jack Nut & Machine Screw	STANLEY 6-Way Screwdriver
Our verdict	Most jobs	Screw won't tighten?	Best-selling fixing	Do it by hand
Use it for	New fittings	Worn or stripped holes	Hollow sections	Screwdriver
Customer rating	New	New	★ 5.0 (1)	New
Length	25, 32, 38, 45mm	25mm	One size	—
Comes as	Packs of 25 or 1,000	Packs of 25 or 1,000	Sold individually	6-in-1
Goes into	uPVC, aluminium, steel	The existing hole	Thin, hollow walls	Hardened steel bits
Price	From £2.99	From £2.99	£0.60	£10.05
Shop	View	View	View	View

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Our counter tip

When a screw won't bite, don't keep winding it in. Stop, work out whether the hole's stripped or you've hit the steel, then reach for a repair screw or a pilot drill. Forcing it is how one loose screw turns into a cracked frame.

The Home Secure counter team, Aintree

1. Using wood screws

Wood screws have a coarse, tapered thread made to push wood fibres apart. In uPVC, that wedge shape can split the profile, and the coarse thread strips easily.

Do this instead: use self-tapping uPVC screws. They cut a clean, fine thread into the plastic and the steel behind it, with a countersunk head that sits flush.

Fitting something new?

Self-tapping uPVC screws in 25, 32, 38 and 45mm. Packs of 25 from £2.99. From £2.99.

Choose your length

2. Overtightening

A self-tapping screw cuts its own thread as it goes in. Keep turning once the head is tight and it strips that thread straight back out, leaving a screw that just spins.

Do this instead: stop as soon as the head is flush and the fitting is firm. On a drill driver, use a low clutch setting and a slow speed, or finish the last turn by hand.

3. The wrong length

Length matters both ways:

Too short and the screw only grips one thin wall of plastic. It'll feel fine at first, then work loose as the handle gets used.
Too long and, on a window, it can hit the glass unit or the seals, or come out the other side of the profile.

Do this instead: match the length of the screw you took out. If you're fitting something new, 25mm suits most handles, hinges and keeps. It's our most popular length, about half of the self-tapping screws we sell. Our self-tapping screws also come in 32, 38 and 45mm.

4. No pilot hole into steel

Into plastic alone, a self-tapping screw doesn't usually need a pilot hole. But when it hits the steel reinforcement, it has to cut through metal. Force it and the screw can snap, the head can strip, or it wanders off line.

Do this instead: if you feel the screw hit something hard, back it out and drill a small pilot hole through the steel first. A pilot hole also helps near the edge of a profile, where the plastic is more likely to crack.

5. Putting the same screw back in a stripped hole

If a screw spins without tightening, the hole has worn too big for it. Putting the same screw back, or another one the same size, just spins again.

Do this instead: fit a repair screw in the same hole. It's thicker, with a deeper thread that bites into fresh material. If even that won't hold, use a jack nut, which opens out behind the wall and gives you a metal thread, or move the fitting a few millimetres to fresh uPVC.

Screw spinning in its hole?

A repair screw bites into fresh material in the same hole. Packs of 25 from £2.99. From £2.99.

View repair screws

Two more to watch

The wrong bit. Many uPVC screws are pozi, not Phillips. A Phillips bit in a pozi screw slips out under pressure and chews up the head. Check the bit matches, and swap worn bits.
Screwing at an angle. An angled screw grips less of the profile and can crack it. Keep the driver straight, and let the fitting's holes guide you.

Which screw for which job?

The job	Use
New handle, hinge or keep in sound uPVC	Self-tapping screw, usually 25mm
Screw spins and won't tighten	Repair screw, in the same hole
Thin hollow section, nothing to grip	Jack nut and machine screw

Our guide to screws for uPVC windows and doors explains each type in more detail, and why screws come loose in the first place.

Need help?

Send a photo of the fitting and the hole to info@homesecureshop.co.uk, or call us on 0151 521 8089. You can also bring the old screw into our Aintree trade counter and we'll match it.

View all tools and fixings

Helpful guides

Screws for uPVC Windows & Doors: Self-Tapping, Repair or Jack Nut?

How to Fix a Loose or Dropping uPVC Door Handle

Are uPVC Window Handles a Standard Size? What We Actually Sell

How to Identify & Measure uPVC Door Handles: Type A vs B, PZ & Screw Centres

FAQ

uPVC is hollow, so a screw that only grips one thin plastic wall works loose as the handle or hinge is used. The usual causes are a screw that's too short, overtightening that strips the thread, or the wrong type of screw. A repair screw in the same hole usually fixes it.

Just tight enough for the head to sit flush and the fitting to feel firm. Any more and the screw strips the thread it has just cut. Use a low clutch setting on a drill driver, or finish the last turn by hand.

Match the screw you took out. For new fittings, 25mm suits most handles, hinges and keeps, and it's our most popular length. On windows, avoid going longer than you need, as a long screw can hit the glass unit or seals.

Match the bit to the screw head. Many uPVC screws are pozi, and a Phillips bit in a pozi screw slips out under pressure and damages the head. Pozi heads have small extra lines between the main cross.

Not usually into uPVC alone. If the screw is going into the steel reinforcement inside the frame, a small pilot hole makes it much easier and stops the screw snapping.