Best 7 fixings and fasteners for PVCu windows

Used to fix your PVCu windows in place, fixings and fasteners are an important part of the process of installing PVCu windows. There are many different types hopefully this blog entry will help you to choose the right one for the job at hand.

Fixing Types

  • Wood Screws
  • Self tapping screws
  • Fischer bolts
  • Anchor bolts
  • Concrete screws
  • Bay pole screws
  • Straps

Each of the window fixings and fastenings above have a suitable use and situation to be used in.

Wood Screws

wood screws for fixing windows
Shanked wood screws

Wood screws can come in many different sizes and types – for installing windows twin threaded zinc coated is what you are looking for. The sizes you will need can range from 4mm or  5mm in diameter and 40mm to 90mm in length. As the name suggests they are for fixing into wood. Most loft conversions are made from wood, out buildings (garden shed/office) and Victorians used wooden lintels . You would need to pre drill a hole in the frame of the window you are fixing through the same diameter as the screw. You then need to position the window and pack any gaps before inserting the screw and tightening. The head of the screw will determine whether or not you need to counter sink before hand for a good finish. 

40mm 50mm 60mm 70mm 90mm wood screws zinc coated twin thread
40mm, 50mm, 60mm and 70mm wood screws

Wood screws are often used to fix PVCu windows to their sills – it is important to pre-drill the frame then drive the screw directly into the sill until it pulls tight – it is a good idea to countersink to avoid the glass fouling on the screw head when being installed later. I would use wood screws for fixing any additional wood supports to wooden lintels. As for actually fixing windows they are not ideal and make for a fiddly and time-consuming installation.

Self Tapping Screws 

gold silver and white topped self tapping screws
Chrome, gold and white capped self tapping screws

Not a screw used to fix windows but to fix things to windows. Friction hinges are often held on Self tapping screws, furniture on sash windows – lifts, bow handles, fitch fasteners – letter boxes and security chains. As well items you can see they can also hold fixing straps to the window. 

One of the great things about self-tapping screws is that you do not need to pre-drill. Self-tapping screws are most effective in PVC or metal. In wood they can strip out easily and do not hold very well. 

self tapping screws for window handles pulls lifts
Self tapping screws

If you are using them to fix into aluminium or steel that is quite thick the self-tapping screw can bite in and jam in the hole making the battery drill slip. If this occurs you should discard the screw and get a new one – as it is very likely you will round out the head of the screw and never get it to the tightness required or it will become stuck. A self-tapping screw could be used to pre-drill for a wood screw if you do not have a drill bit to hand.

Fischer bolts/frame fixings

nylon window fixing for pvc timber casement or sash windows
Fischer bolt

Fischer is actually a trade name for a fixing like Hoover for a vacuum cleaner. Frame fixings come in several different designs but all have the same principle. A plastic sleeve that expands when the screw inside is tightened and pulls a plastic bung up the sleeve making it expand and grip the material it has been inserted into. There are many different sizes – for window fixing I would suggest at least 8mm diameter – thinner 4 and 6mm are available but not really up to the job. The most common lengths required 100mm, 120mm,150mm and 180mm depending on what you are fixing into and through. 

nylon frame fixing for pvcu sash windows and casement windows
Nylon frame fixing

To use an 8mm frame fixing you need to drill an 8mm hole – this will pass through the frame and into the wall – you will need two drill bits – one for the frame like an HSS and one for the wall masonry or SDS bit. You then insert the fixing into the hole until the head is snug against the frame – you may need to use a hammer to tap it home. Once in place, the frame will need to packed either side of the frame fixing to prevent bowing or distortion of the frame when done up with a large pozi drive. These fixings are best used in brick and work well in Aircrete blocks. However, they can make window installation tricky as they can move around when tightened. If a mistake is made or they do not grip and fix they can be difficult to remove – the easiest way is with a claw hammer but it will ruin the fixing.

Anchor bolts

Rarely used for window installation anchor bolts are very heavy duty. More commonly found in commercial applications where wind loading maybe a factor. You may find they need to be used on new build projects for fixing very large bi-folding doors. They are good for securing hooks for window cleaners or fire escapes – but please ensure they are fit for purpose.

heavy duty anchor fixing for bifolding doors or curtain walling
Heavy duty Anchor Bolts

Anchor bolts work in a very similar way to frame fixings expanding when tightening. They may have bolt head, flush Allen key head or tore drive. All are virtually impossible to get out once installed.

Concrete Screws

t30 concrete fixing bit for pvc sash windows
T30 bit and concrete fixing

The best screw you can use for almost everything. When discovered almost 15 years ago they were life-changing – for window installers anyway. Concrete screws will fix virtually anything. The sizes I carry for window fixing 60mm, 80mm, 100mm, 120mm, 150mm and 180mm using 120mm mostly. Most use a Torx 30 bit drive them in – usually found in the box. To fix with the concrete screw you will need to pre drill in both the frame and whatever you are fixing into – wood/concrete/brick – the hole needs to be 1-1.5mm smaller than the fixing i.e. 7.5 fixing needs a 6-6.5mm hole. If you are fixing into something soft like wood or Aircrete go for  a smaller hole but if its hard cast concrete (a lintel), steel or rock use a bigger hole. You won’t need to the pack the frame as the fixing bites into both the frame and wall holding firm – a big advantage for time and when using foam. In Aircrete they can pull out easily –  so be careful if they need adjusting.

concrete fixings for almost anything and pvc sash windows
Pan head (left) and self cutting counter sink head (right)

Concrete fixings come with either a countersink head or pan head. The self-cutting heads rarely work well and you will need to countersink before putting in the concrete screw (extra work) – We recommend using the pan head as it fits snugly against the frame and looks good with less work. You can buy little plastic caps for the countersunk fixings – but they will fall off and a neatly installed bolt looks better. Used for fixing almost everything concrete screws replace plastic frame fixings and work well in place of wood screws for strength and adjustability.

Rawl plugs

plugs for pvcu windows and straps
Using the right size screw for the Rawl plug is important

Rawl plugs seem like something from yesteryear – in window fitting they do not really have a place but they should be in your toolbox. Fixing into plaster they really are the best thing. You may also want to use them if you are fixing straps into bricks or plaster.

rawl plugs for fixing pvcu window straps
4, 5 and 6mm Rawl plugs

Working in a similar way to the frame fixings you drill a hole for the size of the plug/screw push it into the hole and when the screw is tightened the plug expands to grip the hole. These should be used for anything you are fixing to a wall – radiator brackets, large picture hooks, curtain rails, book shelves, TV brackets.

Bay pole screws

self tapping baypole screws
Self tapping pan head – no need to pre drill
pan head self tapping screws for pvcu windows
Baypole screws

An extra large self-tapping screw with a pan head. These screws are great. Best uses are fixing bay poles! As they sail through the PVC and cut easily into the aluminium support inside. They can also be used for fixing sills, straps, add-ons, frame to frame or into metal lintels. No pre-drilling is required so very quick to use. If there is any slipping with the drill when screwing in replace it straight away or risk rounding out the head. If it does become jammed halfway in a good sharp whack with a hammer will break it off – much easier than removing it with pliers or cutting it off. Bay pole screws are not very good for wood. I carry 4mm diameter 40mm, 50mm, 60mm, 80mm and 100mm.


window straps for evolve pvcu sash windows
Window straps as supplied by Quickslide for PVCu sash windows

There are a few different types of straps from widgets, lugs, cleats, brackets etc. They all do the same thing. Straps can be designed to clip onto the window – most will be screwed on. Generally, window straps are awkward to use – but for new build projects, they are ace. When the reveals are yet to be plastered the straps can be put on the window in moments – then packed and leveled all round and simply screw the straps to a wall using Rawl plugs or concrete fixings. Job done. But with replacement windows, it’s rare you will want to disturb the reveals. 

Where to find your fixings and fasteners

These are the easiest places to find fixings and fasteners for PVCu windows

DIY, trade and public suppliers

Trade only suppliers

Buy PVCu Sash windows any size from £299

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