DIY Patio Door Installation Project BISF House

BISF House Patio Door DIY

Hello Everyone and welcome to my photographic diary showing how my good friend Matt and I installed a set of sliding patio doors to the rear of his BISF house.
During the installation we made a photographic record of the various stages of the job.

DIY Patio Door Installation Project BISF House 1

We are by no means experts in this field but we do possess basic DIY skills and we both felt competent enough to undertake this project.

A professional builder may choose a different method of installation to that which we choss, so if in doubt at any stage, please seek professional advice.
This montage is not “A How To” guide, it is simply a record of how we installed the doors ourselves as two DIY enthusiasts.

Installing a set of off the shelf patio doors into your home can make a huge difference to the living space, especially if your house has a separate dining room at the rear of the property and is fitted with a standard window as BISF floor layouts do vary. Our house had a separate kitchen with a dividing doorway into the living room. The double doors leading from the lounge area had already been removed but the dining area still lacked light and area appeared quite dark, despite being south facing.

Installing a new set of sliding patio doors costing well under £500 was the obvious choice to brighten up this area.

By doing the job ourselves we saved quite a bit on labour costs but you could expect to pay anything from £250-£500 labour for a job of this size which should take 1 or possibly 2 days to complete. Our job took 1 1/2 days, which wasn’t bad for DIY but I would expect a good builder to be able to complete this in around a day.


  • Before undertaking any work of this kind always make sure that you have the correct tools and safety equipment to complete the job.
  • The original render has stood in place for around 70 years and could well be in need of repair. Thoroughly check the condition of the existing render, especially in the area surrounding your dining room window, before you plan or start any work.
  • If you see signs of horizontal or vertical cracking, it may indicate that your render is starting to fail. Seek professional advice before you undertake any work, or a large portion of you wall could fall away and require re-building.
  • If your render does appear to be failing, you should have it professionally repaired soon rather than later and seek advice from the builder regarding the best time to install the patio doors. Preferably, just before the wall is re-rendered.
  • Make sure you have a large tarpaulin at hand in case it rains or should you need to temporarily cover part of the wall due to render failure.
  • Electric power and cutting tools will be required to complete this task. Always wear suitable protective clothing including a face mask, head, eye and hand protection. Always use a circuit breaker when using power tools outside.
  • When cutting into any wall or cavity, always make sure that there are no electrical cables running through the wall where you are cutting. Remember that electricity can be fatal.

This job does entail cutting into you rendered wall below the dining room window. Cutting into any wall has risks, much depends on the condition of your existing render which should be sound and in good condition, otherwise you could face problems with  large areas of render falling away which could be costly to repair( Another good reason to call in a professional fitter/ builder).

Matts house, was due to be fitted with external wall insulation within a week, so we weren’t too concerned if the render fell away or not. As it happens it did fall away, but more on that later. It’s also worth noting at this point, that I have installed several patio doors in the past without any problem but I can’t stress enough, that render collapse is a very real possibility, so be prepared to undertake significant repairs if you choose to fit patio doors yourself. You may also need to undertake a small amount of rendering to the newly created reveals too so keep that in mind.

That’s the precautionary warnings out of the way – now to the job itself.

Inspection of our render
Our render was in a pretty bad shape. We could see 2ft wide  but very narrow horizontal cracks in the wall itself,  located to the left side of our window  which spread all the way down to floor level. When then conducted a tap test on the wall and found large areas that sounded hollow underneath. This was a sure sign that our render was failing as it was also ballooning outward slightly, with the top layer separating from the underlying rib lath mesh framework underneath. It was highly likely that rain water had entered into these cracks and frozen causing expansion and cracking once thawed. We also suspected that the supporting rib mesh was badly corroded and this was found to be the case once we started to cut into the wall. Note: Cracked render and corroded mesh doesn’t always mean that the steel frame of the house will be corroded too. In our case the steel support stanchions were found to be in excellent A1 condition which is not bad for a 70 year old property.

bisf cracked render
The appearance of horizontal cracks in the rendered wall is a sign of failing render, due to water ingress and possible corrosion of the internal mesh support

If you see signs of cracking to either side or below your existing dining room window, please think again before undertaking any work such as this. If you do, a large part of your wall could break away and this will require a considerable amount of work to repair. Plus the outside of your house will not be watertight until the repair is completed so please inspect the area carefully and tap the walls first. If you hear an occasional hollow sound when tapping, you may well have underlying issues.


Please let us know what you think in the comments below.

Sadly we did forget to take photographs whilst we were putting together the Patio Door kit as it was starting to get dark and we needed to make the property secure overnight. Assembly was pretty straight forward but I would say that it is definitely a two man job.

We hope you enjoy watching our project and find it helpful.


  1. @leejones05

    Fantastic Lee!
    It looks like you did a great job too, without suffering from any breakaway render.

    I think the biggest issue that we face, is not knowing exactly where the side stanchions are to the nearest millimetre. Of course, we have a general idea thanks to the location of the window frame surround, but it can still be a little nail biting once the work is started, as there isn’t really any turning back once the first cuts have been made.

    I’m glad you persevered, as the door looks great in its new location.

    I can see where the old encasement overlapped the render on the top half of the opening. Out of interest, what was the size difference between the outer edge of the frame, to the inner edge of the stanchion as highlighted in the image below? 


  2. Hi Lee, the stanchions sit pretty much just behind the area that you have highlighted. They are located behind the inner reveal of the windows, which in most original properties are constructed from timber board.

    Take a look at the image below. Despite this photo being of the larger rear window, if you look closely you will see the stanchions on each side of the frame.

    Just remember that looking at the Crittal hope window casing from the outside of the property can be a deceiving as the moulded frame surround is L shaped and overlaps the underlying stanchion edges, making the window opening width appear larger from the outside.

    Also Lee, please make absolutely sure that the render below the window is in good condition. Tap it with a screwdriver handle and try to listen for any areas that may sound hollow. It’s the hollow sections that may cause issues if and when you try to cut out the door opening. I have installed several patio doors myself with no problems but in the instance shown here, we did have a large area of poor render to the lower left side of our intended door opening. The render had separated from the metal render support mesh onto which the original render was applied. It was evident to us that we could face the possibility of part of our wall breaking and falling away, due to the fact the render sounded extremely hollow when tapped along with the presence of wide horizontal cracks running across the surface where water ingress had occurred.

    Once we started to cut the render for our door opening, our concerns became a reality as a large portion of the render that we did not want to cut fell away, leaving a large hole in our wall.(see below image) Fortunately this was not a problem for us as the property was also due to be externally insulated so the entire wall section of degraded render could be removed and replaced with OSB board onto which the external insulation could easily be fixed. However, had the property not been due to be fitted with EWI, we would have been left with a gaping hole in the wall which would have to be repaired by other more traditional means.

    So before you even start a project like this, you should be aware of this risk and have a contingency in place should a large area of render fail, or break away.

    I have included several more images below to assist you. Several depict the stanchion once the inner timber reveal has been removed and one shows the area of render that broke away during the job. What is not shown here is the true extent of the failed render that we had to remove, which was around the size of a full sheet of OSB which covered an area from floor level up to the the start of the steel cladding.

    Please ask as many questions as you like because the more you know, the easier it should be. I wont be able to reply till later this evening but I look forward to your reply.


    1. Hi Marc,Thats great info and to be honest im not sure what situation i would be in now if i had never seen your video, most likely panic stations with a big hole in my wall boarded up ? ? i can laugh now.Well i have managed to sell on my french doors that would have been way to big and now im searching for some french doors 40 inch width max, they are available with a few companies that do made to measure but a bit expensive so im hoping and searching on selling sites for a second hand set, i will keep you updated on how things go but again thank you so much for your help keep up the great work ? Thanks alotLee.

  3. Hi Lee and welcome.

    I can confirm that there will be vertical stanchions running down each side of the existing window frame from floor to eaves level. I have not yet seen anyone install patio doors where the smaller window is located which is probably due to the width restriction caused by the stanchions which cannot be removed.

    Vertical stanchions run alongside all window and door openings in these houses.

    I’ve included several images below to give you an idea of the locations.

  4. Hi Guys,              I was due to install some patio doors and thought i best do some research first and luckily came across your photo video, but i am now worried after seeing your video about the stanchion supports either side of your window, i have uploaded a photo of our house and circled the window i wish to replace with patio doors, could you tell me if you think we will have stanch

    ion supports either side of the window we wish to put patio doors please?Our window frame inside house measures 40 inch wide but our doors measure 46 inch wide, so im worried if we have stanchion supports they wont fit.Thank you for your video i found it very informative, i am a diy’er  myself but will now hold fire until i hopefully have some info from yourselves.Will appreciate any help. RegardsLee.

  5. Thanks for the post! I am keen to know what runs across the top of the opening. I want to remove the steel cases when we get new windows installed so was wondering if this is ok to do without compromising the structure?