Replacing worn out patio doors with Bifold doors

Pre-purchase decisions

Bifold doors are a beautiful addition to any home and can bring the outside in but there are some things I had to consider before deciding to go ahead and replace my existing patio doors with bifold doors.

Doors and windows are a controlled install and therefore require that the installer is either FENSA registered or that the person installing the doors and windows will let building control know before the install or get a Certificate of Regularisation if applying to building control retrospectively.

This blog post records my experience of installing bifold doors as a replacement for old uPVC sliding patio doors.

Assessing the lintel

The existing opening of the old patio doors was the same size as that required for the replacement bifold doors. If it had not have been then there could have been a few tricky alterations to the lintel above the door and the surrounding brickwork. This would involve acrow props and temporary beams and would most definitely have required consulting the professionals. The opening being the right size for the new doors didn’t mean that I could take the lintel requirement for granted. I still had to assess the loading rquirements to make sure the lintel was capable of accepting the extra load of the new bifold doors. This can vary by manufacturer and door type i.e., top hung, bottom hung, uPVC, hardwood etc. The instructions for the doors should specify a Uniformly Distributed Load or UDL which is expressed in Kilo-Newtons per metre.

In my case the Jeld Wen Bedgebury 3 door 1800mm wide bifold doors were described in the instructions as having a UDL of 0.5KN. The existing cavity lintel was a heavy-duty type made from steel with a material thickness of 3mm and the end bearing onto the brickwork (how much the lintel overhangs the opening) was 150mm which is the minimum prescribed by the instructions. In this case it was assessed that the existing lintel had a load which was equal to that of a standard load scenario for a single-family residential dwelling room. This equates to a load of a typical timber floor applied to the lintel, via joists resting on the lintel or on the masonry immediately above the lintel. As a guide, the following construction gives the above dead load: Typical 50x220mm I Beam Composite joists at 400mm centres, 18mm chipboard floor, underlay & carpet, 13mm plasterboard ceiling with finishes, partitions (non-load-bearing stud walls) and services/built-ins such as typical plumbing, storage shelves, sinks & lights. This live load is typical for a more highly loaded domestic room floor. (Refer BS 6399) This gives a total lintel load of 6.0kN/m, which is taken over 1.1x the clear opening span for the load tables, as per BS 5977-1.

Load Details:

–              Dead load of 1.0 kN/m2

–              Live load of 2.0 kN/m2

–              Joist span of 4.0m in total

–              Giving 6.0kN/m on the lintel

Since the instructions specify a UDL of 0.5kN which would add an additional load to the existing cavity lintel of approximately 8.5% which was deemed to be within tolerance for the type of cavity lintel which was present in my installation.

Checking the fit

The doors were listed as being 1794mm wide and 2094mm high. The instructions recommended a +10mm tolerance for the size of the opening. We measured the ends and middle of the opening for height and width. My opening gave a width of 1804mm in the middle and 1800mm at the top and bottom and 2090mm across the entire height of the opening but we knew we had the ability to remove some of the mortar below the existing sill so we could get the required size. We checked the diagonal sizes as well to confirm we could get a true installation of the frame i.e., all sides (left, right, top and bottom) parallel and straight.

Once the doors have landed

The doors are delivered in separate boxes with the frame in pieces in their own box ready to be made-up. The fixtures and fittings are also in a separate box with the with the screws and packers in their own bag. There is a set of instructions on the manufacturers  website that also contain a kit list. I spent some time verifying that everything in the kit list was contained within the parts delivered.

Although two sets of the same door were ordered one set had an addendum sheet tucked into one of the frame boxes saying that sealant needed to be applied to the faces of the frame joints. The other frame came with rubber pads stuck to the faces of the joints which negated the need for sealant to be applied and therefore no addendum sheet. Luckily, I unpacked the box with the addendum sheet first.

I decided which way round the doors should open and in my case the decision was driven by the need to maximise the view out to the garden and to give minimum interference with the traffic around the patio. At this stage I read through the fitting instructions supplied online and made myself very familiar with the installation process and requirements. It’s worth spending some time going through the instructions step by step as this could save a lot of time later on and also prevent costly mistakes. I also found some youtube videos that documented the fitting process and gave some insight into areas that might need special care and attention.

The doors came with the multipoint locks round the right way for my configuration but I might have had to flip them if I had wanted to install the doors opening the other way and with the hinges on the opposite frame jamb.

Demo Day

First job was to unscrew all the fixtures and fittings from the old patio doors and remove them from the opening. As much of the structural integrity as possible was retained of the old patio doors to allow them to be reinstalled in the opening if the new patio doors were not ready to install at the end of the day.

The door casements of the old patio doors lifted out of the tracks without too much bother once the lower plates had been unscrewed from the outside, not very secure. Something the new bifold doors will not suffer from.

Some drywall had to be removed to get to the frame of the old patio doors. The builders had used doors where the frame was fixed to some specially made plastic cavity closures. I am sure this was done for quickness but does seem to lack a bit of structural integrity and the closers did not contain any insulation. Newer versions of these structural cavity closers have fixings into the blockwork to secure them and contain insulation to give the correct thermal barrier.

Adjusting the opening

Once the old patio doors had been removed it was time to turn my attention to the opening. The new patio doors sit back slightly further in the opening than the old ones requiring that a strip of tile and subfloor to be removed to accomodate the new bifiold doors. The original builders had filled the cavity under the old sill with concrete, so it was just a case of running an angle grinder along the tile to the required depth and width and then using a cold chisel the concrete, subfloor and tile was knocked out.

The sill on the new bifold doors is secured with metal strips so three holes were cut in the tile and subfloor ready to allow the metal strips to be sunk to the correct depth and screwed into the concrete subfloor below.

A smooth mortar bed was laid across the concrete below where the new sill was going to make it level ready to accept the packers that would be used to fix the new sill at the correct height and level. A piece of DPC was laid across the mortar bed to go underneath the sill. It was overlapped on the floor and the exterior and would be cut down to size eventually during the making good at the end.

Constructing the frame

It was now time to make the frame up and offer it up into the opening to see how much if any work needed doing to the opening to get the frame to fit square and true. The frame head of the doors has holes pre-drilled with the positions of the screws that will be inserted into the lintel and blockwork above. Strangely though they are not of a big enough diameter to accept the lintel screws that are supplied with the doors, so the first job is to drill the holes out to a diameter just big enough to allow the lintel screws to pass through. The lintel screws that were supplied in my pack were mixed and had two different diameters, so I made all the holes to the size of the largest diameter lintel screw.

This is where my sequence of construction differed slightly to that of the official version in the instructions. The reason for this is because the bottom pivot block is screwed into the sill using a pre-drilled pilot hole therefore it is vital that the block is accurately located over the hole to produce a firm and square fixing, and this may not be the case if the jamb is fitted into the sill a fraction of a millimetre out of alignment and doesn’t butt up to the pivot block perfectly. So, I fitted the bottom pivot hinge block by sliding it into the gully in the sill and aligning the hole in the block with the pre-drilled hole in the sill and driving home the screw. I did use a slightly smaller screw than the one that was supplied in the pack as the origianal screw supplied sheared off when I was screwing it in. Fixing the bottom pivot block in place first allows the frame jamb to be butted up to it and therefore accurately placed when constructing the frame.

With the frame head screw holes enlarged and bottom pivot block in place it was time to screw the frame together. We were installing two sets of doors as mentioned earlier one set came with an addendum specifying that silicone had to be applied to al the mating faces of the frame joints. The other set of doors had rubber pads on the mating faces so did not need silicone. I had to cut the weather seal at either end of the head as it protruded beyond where the jamb would be fitted.

On the first set of doors to be installed they didn’t require silicone on the joint faces because the frame jambs had rubber gaskets applied to them. It was now time to push the joints into their respective housings and make up the frame. I found it easier to elevate the frame off the floor using blocks of wood. This made it easier to tap the sides, head and sill together using a rubber mallet.

Once all the frame pieces were together, I checked the trueness with a square before inserting the frame screws into the pre-drilled holes in the frame and driving them home with an electric driver/drill.

Closing up the cavity and frame installation

The new cavity closers were cut to the correct length and inserted into the cavity. They have an adjustable insulation strip that you cutdown with a Stanley knife to the width of the cavity between the blockwork and brickwork. The closers then have an interference fit in the cavity so that they can be pulled in and out quite easily.

At this point I needed the help of a second person to lift-up the frame and offer it up into the opening. The frame was quite tight on the sides at the top so I took out the cavity closers and used an angle grinder to shave a small amount off the brickwork to accommodate the frame more easily. This would also allow me a little bit of leeway to adjust the frame with packers when squaring it up.

With the frame now being able to fit nicely into the opening I repositioned the cavity closers and we re-inserted the frame into the opening. I made sure the lintel was 1mm proud of the head of the frame all the way along and this also gave me about 35mm of reveal for the brickwork around the frame.

Using a long spirit level I checked the sides, head and sill to make sure they were true and adjusted with frame packers as necessary and made a note of how many and where the packers were inserted so I could easily true up the frame again after I had removed and reinserted it.

I then used a laser measure with a block of wood sawn at 45 degrees and a white label stuck to the face to measure the diagonal distance between the two corners of the frame. After some jiggling around and rechecking that all the sides, head and sill were true I managed to get the readings within 4mm of each other which was as close as I was going to reasonably get.

Fixing the frame into the opening

I then marked on masking tape stuck to the sill where the metal tie straps were going and removed the frame from the opening laying it down on the floor on blocks of wood. Using the positions marked on the sill I drilled pilot holes and used my own self-tapping screws to fix the metal tie straps in place on the sill.

Now it was time to re-fit the frame into the opening hopefully for the last time. With the frame in place and the packers inserted back into the positions I had noted above I rechecked the trueness with a spirit level and also checked the measurements diagonally from corner to corner. All was in order, so the next step was to start drilling the pilot holes for the screws that secure the head but first I just needed to secure the sill and stop the frame from swinging around at the bottom by screwing the screws into the metal tie straps. I only partially screwed them in as the sill will rise-up slightly when the head is screwed into the lintel.

The instructions stipulate that there must be a bow (or camber as they refer to it in the instructions) of 5mm in the head between each end of the head and the middle. I am guessing this is to allow the doors to run in the track without fouling and so they stay in the correct position when fully opened. When you look at the head it is hard to imagine it will bend easily considering it is a solid piece of hardwood 80mm by 140mm in thickness but by driving the screws in bit by bit for each screw working from the outside in it does eventually develop the required gap at either end.

Being careful not to move the frame now it is square and true I started drilling the pilot holes through the existing holes in the head and into the metal cavity lintel. I was careful to make sure the holes were deep enough to accept the full length of the lintel screws that had been supplied. The lintel screws in the pack that had bee supplied required that I drill a 6mm hole through the metal cavity lintel and then to a depth of 80mm in the brickwork above. This meant the drill bit needed to be a minimum overall length of 180mm. This part of the install took some time and drilling upwards into the lintel and brickwork above certainly gave me a good workout as there are 12 screws to put into the lintel.

When the holes had all been drilled in the lintel and brickwork, I was ready to start driving in the screws. I made sure that some 5mm packers were placed at the ends above the head and then some 2mm packers almost halfway to the middle before I started gradually driving in the lintel screws. I was glad I had consumed a big breakfast as driving the lintel screws home took some doing. I Kept working from the outside in until the head was tight against the packers, and I had the desired bow running from then ends of the head to the middle.

With the head screwed firmly into place I added some packers under the sill to make sure it was resting nicely on the mortar bed. It was now time to secure the jambs. This involves drilling five equally spaced 6mm holes through each jamb using a brad-point wood drill and then drilling 100mm into the brickwork using an 6mm masonry drill making sure the hole was deep enough to accept the framing screw. The hole was then countersunk, and the self-tapping framing screws driven into the brickwork. Before and after driving each framing screw in I kept checking the frame for squareness.

Getting to know the bifold doors

At this stage I had to work out if the intermediate carrier hinge pivots were screwed in the right way round for my installation and adjust, as necessary. Now was also a good time to get familiar with the doors and place them in the right order and orientation ready for drilling and fitting.

I went round each door making a note of the housings and how they related to the door numbers and what way round the doors went. Below are the notes that I used to identify each door to make it as easy as possible to select the right door in the correct orientation when it came to fit them. 

1st Door

–          Slide bolt housings on right at top and bottom.

–          No weather strip seal on slide bolt side.

–          Window glazing bars/beads on outside.

 

2nd Door

–          2 Weather strip seals on both sides.

–          Window glazing bars/beads on outside.

 

3rd Door

–          Multipoint lock on right.

–          Spring latch above deadbolt.

–          Spring latch flat side facing out.

–          Weather strip seal on outside.

–          Deadbolt below spring latch.

–          Window glazing bars/beads on outside.

 

In the installations I performed the doors were hinged to the jamb on the left hand side of the frame and the multipoint lock was fitted to the door on the right with the hook and latch keeps on the right-hand jamb as you look from the inside. 

Next, I fitted the top block for the pivot hinge by sliding it up into the cut-out in the track and pushing it along to the end. Then I offered up the fixing plate (it can be a bit fiddly to get over the spigot in the top block) and marked the position of the screw holes and pilot drilled them with a 3mm universal drill bit. The screws that were supplied in the pack were too big for the 3mm pilot holes and would have protruded too much also to make them fit would have required a bigger pilot hole which in my view would have compromised the integrity of the metal in the track, so I used smaller screws. If you have the opposite handing to the way I have fitted my doors, then you may need to do the intermediate carrier step first (see next paragraph) because the top block fixing plate will cover the cut-out in the track and stop you from inserting the intermediate carrier hinge.

Place the intermediate carrier hinge into the track via the cut-out at one end of the track and leave it hanging in the middle of the track.

Fitting the hinges

I spent a fair bit of time working out what hinges went where checking the instructions and images on the Jeld-Wen website.

Using the notes in the previous section to select door number one, I placed it on trestle tables with the glazing bars facing up. I removed the weather strip from the side where the hinge was going to be attached and made a note on some masking tape and stuck it round the strip so that I knew where it came from. Using a piece of wood 15mm thick as a spacer at each end of the door I placed the pivot hinge against the door hinge face hard up against the spacer making sure the knuckle of the hinge was tight against the door edge and that the hinge was on the correct face and side of the door. Holding the hinge firmly with one hand I then drilled the 3mm brad-point bit pilot holes using the hinge as a template. This process was then repeated for the second pivot hinge. I then drove the screws in using the torx bit supplied with the doors.

 

Moving on to door number two, removing and labelling the weather strip and placing the door glazing bars facing down this time and using a tape measure I measured and marked 60mm from each end to position the cranked hinge large leaf side against the face of the door so that the knuckle was hard up against the edge of the door. Holding the hinge firmly in place as a template I drilled the pilot holes and drove in the screws. Then I measured and marked 936.5mm from the top of the door and fixed the middle half offset cranked hinge with handle in the same way.

Door two in my configuration has the pivot hinges on the other side so I flipped the door over on the trestle tables and measured 39mm from the top and bottom of the door and with the knuckle firmly up against the edge of the outside of the door drilled and screwed the small leaf of the hinges, with the three screws, into position. The carrier hinge being at the top and the intermediate guide hinge at the bottom. Then I measured 960.5mm and drilled and screwed the small leaf of the middle flat hinge into place.

 

Hanging the doors

Now with all the hinges fixed on the doors they were ready to be hung into position. This definitely required the services of two people. The first door to hang was door number one. The key to an easy install is for one person to hold the door in position having placed the bottom hinge over the pivot post and resting it in an upright position and the other person guides and screws the top pivot bolt into the top block housing. The yellow plastic lock ring needs to be screwed on the pivot bolt to stop it falling out of the hinge cylinder while the door is being positioned. I used an 8mm ball end allen key hex bit fitted to a socket adapter and extension on a square ended socket screwdriver to make the adjustments to the pivot bolt.

 

Next, I hung the second door. This is a similar process to the first door but this time, still using two people, we placed the intermediate guide into the gully in the sill and holding firmly onto the door positioned the intermediate carrier hinge below the housing and while one person steadied the door the other person screwed the bolt up into the carrier housing.

 

While one person maintained a firm grip on the door the other person used a hydraulic jack raised up below the two doors with a piece of flat wood in-between the jack and the doors just touching the bottom of both doors to make sure they remained together at the same height. Then the small leaf of the cranked hinges was placed against the face of door one and used as a template to drill pilot holes and then drive home the torx screws.

 

To hang the third door requires creating a platform to support the door while it is screwed into position. As per the second door we used a hydraulic jack to raise and support the third door to the height of door one and two. Other ways to bring door three to the correct height might be bricks, kitchen steps or blocks of wood while utilising packers to attain the desired height. Once door three was at the correct height one of us steadied the door while the other made sure the large leaf of the door two hinges were flat against door face and drilled and screwed the hinges into position.

Then I pushed the weather strips back into their channels on the doors making sure to get the correct weather strip into the right groove and the right way round (There are three types of weather strip with different profiles). The strips have to be cut to size where they butt upto a hinge. There are some small strips of 15mm at the end of some doors where there is a small gap at the top between the hinge and the top of the door.

Adjusting the doors

 

We are on the homeward stretch having fixed the frame and hung the doors. The next job was to adjust them to make sure the gaps at the top, bottom and sides are set to the correct tolerances. Using a long reach large size screwdriver I adjusted the screws in the top and bottom block so that the side gaps were parallel and around 8mm at the multipoint lock end.

Using the ball end allen key I adjusted the pivot block and intermediate carrier bolts so that the gap along the top and bottom of the doors between the door and sill and door and head was about 5mm.

 

Fixtures and fittings

The doors now have a good fit in the frame so this is when I added the fixtures and fittings. First the keeps in the jamb that will accept the multipoint lock latches, deadbolts and hooks. For my installations the blanking plates and keeps were round the wrong way so I had to swap them over remembering to swap the spacers as well that go behind the blanking plates. Then I fitted the drop-bolts which need to be fitted with the single screw accessible through the hole in the slide when the slide is two thirds down or up dependent on whether it is the bottom or top one.

Last fixture to be fitted is the handle. For this I made a template up using the handle as a template. The two bolts that screw the handle together I drilled using a 12mm brad-point drill bit. For the keyhole I drilled a large 20mm hole and a smaller 12mm hole one above the other and joined them up by cutting the sides out with a multitool fitted with a wood plunger. I painted the freshly drilled timber with some exterior wood paint that matched the colour of the doors which was Anthracite Grey RAL 7016. Then after allowing the paint to dry for a while it was a case of fitting the handle with spindle and screwing in the bolts.

 

Final adjustments to the doors

It was time to see if the multipoint lock was lined up with the keeps and if so would the doors shut properly? I pulled the doors shut throwing the drop bolts top and bottom and attempted to pull the handle up on the multipoint lock. It didn’t want to go so now its was a case of identifying where it was binding with the keeps.

 

It was easier to pull the weather strip off the third door so I could see the path of the latch, deadbolt and hooks when I pulled the handle up. The deadbolt and latch were binding on the side of the keep and were not being allowed to penetrate the keep. There was adjustment on the latch keep but none on the deadbolt keep. I adjusted the latch keep and that now went fully home into the keep but the deadbolt was still binding. No matter how hard I pulled the door into the frame I could not get the deadbolt to shut. The only option was to shave some of the side of the deadbolt keep away which I did and that allowed the deadbolt to go all the way into the keep.  

 

The hook at the top of the multipoint lock was also catching on the top of the keep so I dropped the doors down ever so slightly by screwing the bolts down on the carrier and intermediate hinges. This allowed the top hook to engage in the keep but now the bottom hook was binding on the keep plate. There is no vertical adjustment on the keep plates so it looked like the only option was to machine a little bit of metal off the bottom edge of the lower keep plate. I removed it from the jamb and used a cone shaped metal rotary rasp in an electric drill to remove some of the keep plate lower edge. Removing about 1.5mm was enough to allow the lock to work properly and now the doors operate very smoothly. I did apply some white lithium spray over the hinges and in the carrier and track to aid operation and help preserve the finish over time against the elements.

 

Making good

The kit supplied comes with a lot of white and brown screwcap covers. I’m not sure why they are included in the fixtures and fittings pack as they do not match any of the colours that are used in the manufacture of the doors. I purchased some large flat 20mm disk screw cap covers that had a slight grainy texture to them. Although they were grey the match was not good for the colour of the frame so I glued them over the ten framing screws in the jambs and then painted them with the Anthracite Grey RAL 7016 paint that I already had.

Next on the make-good list was the dry wall around the opening. For this I nailed up some battening just to give the drywall some structural stability at the junction with the frame as I wasn’t planning to put any cloaking strips round the outside, so I needed to make sure there were no gaps or play in the drywall. I butted the drywall up to the old dry wall and the plastered the joint to form an external corner. I then ran a bead of CT1 down the joint between the drywall and the frame and smoothed it over with my index finger dipped in water.

 

Once the plaster was dry I cut up the four skirting boards which in my case had a profile called Ogee and then dot and dabbed them into place and filled in the gaps with some filler.

 

When the filler that I had used to fill the gaps in the skirting board was dry I gave the boards a quick sand down just to remove any blemishes and then it was ready for paint. A couple of coats of primer and then two of the topcoat gave a good finish on the walls and primer and white gloss on the skirting boards.

 

The final part of the project was to cut the cloaking strip, which I managed to source with an Anthracite Grey finish that matched the doors quite well, to length and stick it down over the joint between the tile that had been cut with the grinder and the frame using some CT1 sealant.

 The process was somewhat complex requiring precision and patience and a alot of effort in places but the end results were both rewarding and satisfying.