Costs of Making The Lean-to or Outhouse Part Of The House?

Costs of Making The Lean-to or Outhouse Part Of The House? 1

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Hi all,

Me again! So the house got a structural survey today which I should hopefully hear the results back from this week (im still very 50/50 on whether it will actually happen), and went back today to take some pictures to help me better plan the project while the sales process goes on.

It would appear alot of my plans hang on making the current lean to/outhouse part of the house itself. At the moment the house is in its original form, with an outside toilet and fuel storage. So what Im wondering is what is involved and the potential costs with making this lean to a more permanent part of the house which I see is done very commonly- ie to make it into a utility room and downstairs toilet/ extension of the kitchen, etc etc. Ie are the current walls fit for this purpose? Or would it be better to knock this down and rebuild with bricks with appropriate cavity insulation? The roof will need doing either way as ive noticed a big hole above the entrance to the back door (which I really hope isnt going to be a reflection of the condition of the main roof)- but cant figure out if its as simple as simply bricking in a new external door and rendering around, or if its a rebuild job?


Grangey :)


  1. Thanks Marc I hadnt seen Ed’s picture- certainly seems very likely its blockwork which makes my life alot easier! Although I still have to replace the roof to it which I assume is also asbestos (its not flat).

    The good news is the property passed the valuation survey so clearly its mortgageable so assuming my structural survey doesn’t come back with anything too negative that Im not expecting then it’ll be full steam ahead! As soon as I get the results through I’ll get some builders round to get some proper quotes to get this done and then I will release my full renovation plans Smile

  2. Hi Marc,

    Thanks so much for your response. Obviously its late so Ive not had a proper chance to digest what youve said so will give it a proper read tomorrow but I do have one simple question from what youve said. You clearly stated your outhouse/lean to was wood…. Was it obviously wood? Ie could you tell it was wood from looking at the outside?

    The reason I ask is Ive seen a number of diagrams that make it appear that this outhouse would be obviously boarded up with wood, however mine looks more like this one:

    apart from this one has had done what Im asking (external door is where I currently have a gap with the toilet to the left and fuel storage to the right).

    So did yours look like the above picture or was yours obviously wood? Im half hoping yours was obviously wood clad so there is a chance mine is breezeblock or something saving the need to rebuild….

    Would be interested in hearing from you! Smile


    1. Hi Grangey
      Yours looks like it could be block like Ed’s outhouse.
      He has previously posted some images in this post HERE

      Mine was visibly exposed and treated wood. I have some images will I will try to root out tomorrow of a neighbouring outhouse to show you.

      I’m just about to log off at the moment but will catch up tomorrow evening.

      Marc Smile

    2. I managed to hunt out the outhouse image before signing off for the night.
      This was a vacant neighbours house undergoing renovations by the council. They kindly let me take a couple of snaps of this timber outhouse in almost original condition.

      As you will see, it’s instantly noticeable Smile


  3. Hi Grangey
    I have recently finished this exact same project on one of my properties, (well that’s if 12 months is recent).

    The original house had a wooden outhouse standing on a raised concrete plinth, There was a narrow flagstone path and then a neighbours garage wall.
    Doing the majority of the work myself I would estimate that the cost of the project was around £3500.00.
    I ripped out the old outhouse and toilet. Caution here as the toilet walls are often covered in asbestos cement board. The path was located about 6″ below the plinth so I removed all the slabs and dug down about 2-3ft if recall correctly and then dug out the foundation trench for the walls. I laid concrete in the trenches and hardcore over the remaining surface area where the path was.
    A local builder friend then built the walls out of block and brick but had a heart attack half way through so I completed the rest. I laid around 2ft of concrete over the hardcore bringing the level up to the plinth. I then covered the entire floor area with a concrete screed and of course I forgot to mention a damp proof membrane was added.
    I had another friend install roof joists for a pitched roof which I over boarded. On top of that I laid a Firestone membrane which was bonded to the roof boards as this was much cheaper and easier than felt.
    I purchased two UPVC doors for the front and back and fitted both. BTW even though the outhouse was built from timber the front and back elevations were the standard single brick skin walls that had been rendered. These were in good condition and left in place. The new brick work was then tied into these.
    Inside I installed a new toilet and sink, some great designs can be found online at reasonable prices.
    I built a new enclosure for the toilet and to save space I installed a sliding wood door which work very well. The roof void was insulated with Kingspan and over-boarded. The walls were lined with a damp proof membrane, studded, insulated and boarded with silver backed plasterboard. The electrics were installed before boarding and I installed all the plumbing including washing machine and sink points, although I haven’t used these yet.

    All in all it has made a massive difference to the house and of course doing the majority of work oneself saves on labour.
    In my view it was much easier to work with what was already there and it saved me at least £1000 keeping the existing walls and foundation plinth.
    If you decide to do it yourself, buying a used cement mixer will save you a fortune. Also having a trade account can be an advantage for buying materials. I had access to a shared trade account at Dewsons for members of a Landscaping Forum that I use, this saved me around 30% in costs.

    Much will depend on what you already have in place but overall the process is pretty easy.
    Obviously this is a condensed account but I hope it helps.