How to Fit Replacement PVC Plastic Framed Windows

Before removing the old window, double check that the replacement window will fit in the hole. Simple I know but you would be amazed at the number of mis-measures I have come across! A lot easier to live with an old window a bit longer rather than a large hole for a few days!

To remove the old wooden window you will need a nail bar, hammer, a glass cutter and an old wood saw. Also dust sheets, dust pan and brush, buckets for broken glass, bags for timber and vents and a vacuum cleaner to clean up.

First remove the opening windows or vents. Lever the hinges away from the frame with the nail bar with the window part open and you holding onto it to stop it falling. Avoid breaking the glass – it makes such a mess to clear up.

Next, remove the fixed panes of glass. Take the glass cutter and score the glass diagonally. Push one quarter and if the putty is rotten you may be able to get the segment in one piece or at least a large piece. With one segment away remove the top segment next to avoid it coming down like a guillotine!  Don’t be afraid of glass but grip it firmly to avoid it slipping in your hands.

Once the glass is removed you saw through the frame with the intention of removing the frame in sections towards the middle of the opening – not outwards or inwards. Saw through at an angel any mullions or vertical members and wrench out from their tenons into the outer frame. Be careful of any bits of glass left in the mullion.

Next saw through at an angle the side frames. You will only be able to get 95{35765b1a37518245d093f60eec45d0b07cf240b543885738cbb8fa5e95b94af7} of the way through due to the plaster on the inside or the render on the outside. Work the straight wedge of the nail bar into the saw cut and lever the frame into the middle. Either it will split or you can finish sawing through.

Saw through the head or top of the frame and take care if the frame has ears or extensions beyond the main opening as these can dislodge bricks or render.

Saw through at an angle the bottom frame and cill taking care not to cut into the window board (the inner ‘cill’) which is usually retained. Angle the cut so that the frame can rise up a bit but removed outwards. This is because the window board is usually tongued into the frame but not usually fixed with pins so only the paint may be ‘sticking’ it together.

Once the old window is removed, snap off any old nails sticking out, flatten brick ties against the bricks and vacuum up dust and cobwebs. Clear away the debris, clean the dust sheets and replace.

Fit the New Window Frame.

You will need masonry hammer drill, screwdrivers, wedges, spacer shims, screws and plugs and the installation kit of parts that come with the window.

Remove the glazing beads and mark (where not seen) left, right, top and bottom. Remove the glass sealed unit and prop against the wall well away from the work area and away from doors opening on to it and similar dangers.

Remove all opening vents so that the hinges go with the vent.

Fit the new cill to the frame having trimmed the cill to the correct length if supplied over long.

The uPVC frame can now be quite flexible if it is the type without a steel core so care must be taken to fit the frame square and vertical without a twist, bow or racking. The glass will always be flat and will not take kindly to any attempt to twist it to match the frame!

Drill, plug and screw through the holes provided in the frame into the brickwork or timber frame carefully fitting the packing slips so that the frame is firmly secured yet not bowed and with an equal gap all round. Fit the plastic caps to cover the fixing holes. Bed the bottom caps in mastic to stop leaks.

Now is a good time to seal the frame to the brick with silicone mastic. If you are not used to a mastic gun (and there is quite a skill to use one and get a good finish) then mask up the brickwork and frame first with masking tape. Let the mastic cure a bit before removing the tape. Resist the temptation of smoothing the mastic after removing the tape or you will battle with cleaning the frames in the future by lifting the feather edge of the mastic.

Place spacers to raise and centralise the fixed sealed unit and if working alone make sure the glazing beads are within reach as one hand will be required to hold the unit in place while you clip at least one bead in.

On windows with a good design, the beads are on the inside. I have seen them on the outside but then there is nothing to stop a burglar removing the beads and the glazing to gain a very quiet access!

Next fit the inner glazing gasket. You will battle with this unless you compress the sealed unit against the outer glazing gasket first. You will need some wide timber wedges to achieve this, cut at a fine angle and with the feathered ‘nose’ cut off to allow the wedge a bit of travel. You will need to size the wedges to suit the job but that will be obvious. If you have a lot of windows to do then I cut them from oak. Keep the wedges clean and free of grit which would scratch the glass.

Start fitting the neoprene glazing bead at the top middle leaving a loop hanging as you go to avoid stretching the bead. At the end of the job the bead needs to be in compression, not tension.

Nick the back of the bead in the corners to get a nice tight turn yet keeping the bead continuous. Work round the frame till you are back to the top middle. Trim the bead nice and square so the join is almost invisible. Remove the wedges and work the bead home which will help with compressing the bead.

Fit the opening vents and adjust for a good, draught proof fit.

Run round the inside of the frame with decorators caulk to seal the frame to the existing plaster but if you made a good job of carefully removing the old frame there should be hardly any making good to be done.

Clean the window of finger prints, clear away tools, hang the curtains back and vacuum the floor.

Job done.

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