BISF House with Brick cavity wall

BISF House with Brick cavity wall 1
BISF House with Brick cavity wall 2

Hi There, Been lurking for a few weeks and have a question for someone in the know.
We bought our BISF house about 6 years ago and realised very quickly that during the autumn / winter it would get very cold (our heating bills were astronomical for that first year) we decided to have the entire house externally cavity walled.
We got planning permission and had everything done correctly (proper foundation work, a DPC layer 2 or 3 bricks up, anchored to the house correctly, concrete lintel by the waste, full insulation in between)

We are now selling the property and the buyers valuation surveyor has come back saying that he wont value the property because the air bricks are in the wrong place (initially he said that he wouldn’t value it because there wasn’t evidence of a certificate (which he refused when I offered it to him when he came round to do the survey) and he said there were no air bricks (of which there are 4 near the kitchen)).

Firstly I haven’t seen any other BISF houses that have an external cavity wall, and secondly where should air bricks in a cavity wall be located?

Thanks for any advice.


  1. Hi

    I think everything is ok!

    The buyer recieved his report over the weekend and was obviously concerned with the highlight of “possible asbestos" in the property.

    Have to say, this is the most down to earth buyer that i’ve dealt with. He admitted taking the report findings with a pinch of salt and knows that surveyors generally “find things" to cover their backs. He asked to come round just to see the extent of the findings.

    I’ve attached 2 pictures. one shows a wider shot of the affected area, and then one is localised detail. Please ignore / forgive the cheap MDF panel thats sitting there. i’ve actually made that box into a networking rack of sorts when i cat-5’d the house so all the networking runs into that void (perfect unused wasted space!)

    The buyer is actually a double glazer by trade, so is exposed to different building materials on a daily basis. He caught something that I didn’t and straight away i realised that it wasn’t an asbestos panel.

    In the second picture, i have highlighed what is obviously the original hardboard panel. It then looks like this has been rendered over with some sort of grey plaster / mix before being papered and then painted.

    Suffice to say, the worries have disappeared and we are now both looking forward to exchange of contracts!

    what do you think?


  2. I will take pictures of that one wall tonight and post it back.

    If you can take the pictures off the website, I have no issues with sharing how it looks. FYI the URL is

    As you can see, the open plan makes the room extremely bright and spacious. an added bonus of doing the cavity walls means that the windows need to be moved on to the cavity wall, which then creates these extra deep window sills. As the Living room window pretty much goes down to knee height, we made a long cushion that we put on the sill and my daughter loves sitting there.
    I was an interior designer specialising in bathrooms, and so was able to put the right things in, given the limited space!

    Thanks for the positive comments…it looks like things with the sale are going ahead, although we didn’t get the price we wanted due to stamp duty threshold…its like we are being penalised for wanting to make our home nice. There are plenty of Standard BISF houses that haven’t had the extent of work that we have done to out house that are priced the same…bit of a kicker but can’t do anything about it

    1. That would be great, as perhaps we may be able to help with identification.

      Thank you also for sharing your images, I hope to do a post at the weekend showing the benefits of the open plan effect.

      The occupants of the house we had bricked are away at present so it’s hard to get a view of the back of the property and the air vent locations.

      Heres a google street view image that is a few years old now. It shows the front of the house and the extension. Like your house we spent a great deal on this property, bricking the outside with cavity walls and opening up the living room space. The total costs we around £40k but when we came to sell the property it only reached slightly more than nearby houses that had not been renovated at all.
      It was a valuable lesson for me. It does appear that these properties do indeed have a threashold value depending on the location. Spending very large sums in renovation does not appear to significantly increase the value unless you add a two storey side extension with a fourth bedroom.

      I still need to find my original plans and post them here for the benefit of other members. Once I get a spare minute I shall root them out, scan them and upload them to the site.

      There is so much waiting to be posted but at present other commitments are holding me back. Roll on the Autumn, as I will have plenty of spare time. :0)

  3. Hi Anup
    I see that your home is now being fully advertised by your estate agents and I must say, I really like the open plan feel and your bathroom looks fabulous!
    Would you mind if we shared some of your images for the benifit of other owners who may also be interested in removing the living room / hall wall?

    I’m glad to hear that you have this sorted now, and I hope that everything goes smoothly from now on.

    As for the asbestos, do you mean that they think the boxed unit located above the stairs is made from asbestos?

    Almost all that I have seen to date were made out of hardboard sides with a solid top.

    Do you have any close up images that we can see of the material they suspect it to be?


  4. Hi Marc

    Thanks for your post. I wasn’t sure if there was anyone else on the forum who had this experience with the brick skinned BISF homes.

    It turns out that the buyers lenders had instructed Colleys surveyors to do a valuation survey (not a HomeBuyers, as i thought). essentially it went back and forth in who should pay for the buildings survey. eventually (for sake of speed) i agreed to foot half of the bill.
    2 dates were booked and then cancelled last minute by the buyer, and then it turns out that they are not eligible for a mortgage because they cannot show 3 months worth of salary history.

    Buyer no 2 has jumped on board, had his FULL structural survey last week and the indication i got from the surveyor was that there were no major issues. the only concern he had is one of the internal walls (small bedroom where there is a boxing because of the stairs) looks to be a asbestos board one (i think its the only one in the house as we had all the other rooms plasterboarded) not sure how critical this is as he said as long as its left alone, there shouldn’t be any issues.

    anyway its all in the hands of the solicitors now…the long painful straight now.


  5. Hi Anup, sorry to hear that you are having problems with your surveyor. We had one of our properties brick skinned with a cavity some years ago and never had a problem when it was sold.
    I cannot recall where the air bricks were in the rear of the property but I will try to dig out the original plans. As the house isn’t too far away from me, I will also try to obtain some images at the weekend.

    Where are the air bricks situated now? Are they closer to ground level or are they at near ceiling height?

    Is it possible for you to upload an image of the rear of your property?

    I think in these situations it is always worth obtaining a second survey from a different surveyor as in our experience surveyors do make mistakes and lots of them. This is particularly evident when it comes down to non standard constructed houses as they simply have no experience with these properties.

    Who supplied this surveyor to you?


  6. Hi Ed.
    Its a single layer of bricks with a cavity between the bricks and the original structure. We haven’t touched the ventilation of the original structure, and i believe they’ve allowed for this ventilation

  7. I’ve never seen a bricked up BISF house, probably because there are hardly any brick buildings in Bath so one would stick out like a sore thumb!

    I’m no expert, but I believe it’s absolutely critical to keep the original cavity (ie the gap between the steel frame/cladding and the internal plasterboard/hardboard lining of the walls) very well ventilated to prevent any condensation from forming, or to evaporate it quickly if it does.

    By a brick cavity wall do you mean a single layer of bricks with a cavity between them and the original structure or a double layer with a cavity between the two brick layers?