block and beam subfloor airbrick issue 24 January 2021 at 3:50AM edited 2 February 2021 at 11:25PM in In My Home (includes DIY) MoneySaving 8 replies 111 views

susanna1

1990s bungalow with  an add on conservatory ( for summertime use ) to one end of back elevation. Bungalow has had cavity wall insulation retrofitted since.   Subfloor airbricks(red plastic type) are on opposing sides to front and back (which are the longer elevations) only. 1 of these was venting into conservatory as floor was not raised to subfloor height of bungalow (never picked up by buyers survey in 1999  who just put that airbricks would ideally be on all 4 elevations). Bungalow has been handed down through family since. Subsequently had one additional subfloor airbrick (terracota brick type) added to side elevation of bungalow towards the back. The airbrick is positioned 500cm approx  from corner end so that it presumably helps ventilate area of void where airbrick has been blocked.  Building control  advice sought over phone but not forthcoming as its not a recent build.   Airbricks are positioned at second brick level above ground level. Have no idea whetehr these are the periscope type or not and cannot poke knitting needle through to ascertain due to integral mesh. However the additional airbrick enables knitting needle to go straight through to void.  We are aware of  an amount of powdery dry white substance  which came out of a viewing hole during installation of said airbrick. We were able to ascertain that this was not the cavity wall insulation as originally suspected. The only comment made by the person checking cavity wall insulation was undisturbed was" is this a solid floor" (which  we have subsequently learnt is what block and beam can be classed as).  It was also noted that a DIY liner for the airbrick of some sort had been placed through the cavity wall. The brickwork is double thickness to above  the level of the airbricks. Do we leave as it is/cover it over/look at its removal or block it off. One similar build on estate which faces same direction as ours has their airbricks on shorter side elevations only. Rest like ours, have them on long elvations only.

tacpot12

I can see that you have tried to describe the configuration as best you can, but it's not clear exactly what is where, and it not clear which airbrick you are asking your final questions about. A diagram and photo might help others make more sense of the situation and the questions. 

susanna1

ok..not savvy with adding diagrams..so maybe I can clafiry.
One terracota airbrick has been placed into the side elevation of bungalow. No other airbricks exist along either side elevations. All subfloor airbricks are positioned along the front and rear elevations only. With the one which vents out from the subfloor void directly into the conservatory being blocked off, and being positioned towards the end of the  rear elevation it seems the rationale for adding the odd airbrick was to compensate by ensuring there was still adequate  ventilation  of the block and beam subfloor void. Is this acceptable ?  Apologies for diagram
                       
           l--[[--xx---------------]]---------  rear wall elevation--------         
           =
        
           l-----aa ---bay window--------     front wall elevation ( aa indicates opposing airbrick)                                             
             a bay window area extends out at front                
       
        xx indicates  blocked airbrick                                                                                        
      [[      ]] indicates where add on conservatory sits along outside of rear wall
      = indicates airbrick whiich has been added to side elevation to ventilate bungalow subfloor         void
            

DevilDamo

Completely confused. Can you take and upload any photos?

susanna1

really trying to upload a diagram..;hope this is ok to see.. and a bit easier to understand. I just want to know whether this additional airbrick  will be ok or not. 

grumbler

..............

DevilDamo

So you have one airbrick that has been blocked up as a result of an extension? That’s fine. You don’t need to put the additional one in. Air flow on at least two opposing sides is what is usually required.

susanna1

the arrow indicates where the airbrick has been added to try and compensate for the blocked one. All other airbricks remain as shown.  The additional airbrick has already been added and  been there for a few years..so what should i do.? Do now have to find someone to remove or block the iarbrick that was added or leave it as it is??

DevilDamo

If it’s not causing any problems, leave it.