Is it DIY-able or Approximate Cost

[TheMadProf]

First time posting people.

We're in the process of buying a house and the surveyor has identified a serious issue with inadequate sub-floor ventilation. It's a end-of-terrace, Edwardian place with a fairly old rear solid floor extension.

The surveyor recommends that we add additional air vent bricks to the front and side of the property and repair/replace the existing ones. This seems easily DIY-able to me.

However, he also said that we need to dig up the floor in the extension and install new air bricks linked 100mm ducting to run in channels under the extension floor to the back reception room. Is this possible/sensible to attempt myself and if not does anybody have an idea of the rough cost?

 

[freddiemercurystwin]

Everything is DIYable! But is it necessary? Surveyor's are usually high on crack BTW!

Post the existing plan showing where the existing air bricks, the extent of the suspended floor are and where the concrete floor is and maybe some photos.

 

[tony1851]

Surveyor's are usually high on crack BTW!

So it's not just techies, then?

 

[theprinceofdarkness]

Depending on the construction of the solid floor this can be anything from easy to nigh on impossible.
The worst case is a "modern" floor. It will have 70mm of screed (tough concrete), then 2 or more inches of foam, then a plastic damp proof sheet, then perhaps a bit of sand then 6 " of concrete then earth. For your ducting I would use two 68mm drain pipes. You do not want anything too tall. So you have to cut away the screed and some of the insulation, to get your pipes in (allowing say one inch to cover them), say 4 inches in total. Oh yes and your slot must be the two 68mm plus an inch either side and inbetween, err, that's 8 3/4 inchs wide.
So you mix up some sharp sand and cement , plodge it into the groove and try the pipes out, once you have got a reasonable coverage of their lower surfaces, leave the pipes in and tightly pack the sides, beware, the pipe will tend to rise!!, fill the slot to the top. Leave 4 hours then smooth the top of level with the existing floor level.
I would not do this at this stage, just try out the air bricks at this stage. If the damp persists, then there is no alternative! The problem with it is that the screed spreads your weight over a large area of the foam. If the edge of the old screed is unsupported by the new cement then it will start to crack and fall apart.
Frank

 

[TheMadProf]

On the phone, the surveyor has said that venting this room is obviously the gold standard.

However, if we lift the floorboards and there's no damage to the timbers we could take the view that adequately venting the rest of the house may be sufficient....but be aware that another surveyor will highlight the issue next time around.

What concerns me more is whether or not there's any rotting to the floor timbers. One room has suffered very badly from damp and the floor is a little bouncy. But the vendor doesn't want us sending in somebody who will lift the floorboards pre-sale.

 

[jeds]

The surveyors advice isn't bad for a crack head. Poor venting of floor voids can lead to rot and all sorts of nasties. If he spotted potential blocking of ventilation due to a solid floor or poor vents then he has to mention it. Lift a few floorboards and see what's going on beneath. If the timbers are good and dry then no problem. If not get it sorted. Also bear in mind how the house has been occupied. If the floors have been exposed they will gain a lot of ventilation through the floorboards. That might change if you put wall to wall carpets down or add insulation.

 

[gregers]

What concerns me more is whether or not there's any rotting to the floor timbers. One room has suffered very badly from damp and the floor is a little bouncy. But the vendor doesn't want us sending in somebody who will lift the floorboards pre-sale.

really,why not.what do they know,or trying to hide??

you could vent another way,rather then going through the concrete floor,come off another vent/s on the side using pipework,might be a longer run though but it might be easier to thread it through to the dead spot.

 

[drpepe]

On the phone, the surveyor has said that venting this room is obviously the gold standard.

However, if we lift the floorboards and there's no damage to the timbers we could take the view that adequately venting the rest of the house may be sufficient....but be aware that another surveyor will highlight the issue next time around.

What concerns me more is whether or not there's any rotting to the floor timbers. One room has suffered very badly from damp and the floor is a little bouncy. But the vendor doesn't want us sending in somebody who will lift the floorboards pre-sale.

*SLIGHT ALARM BELLS*

Our surveyors noted a damp problem in our current house, but the vendor wouldn't allow any lifting of floorboards (not even the doormat well hatch).

Needless to say, 18 months later we have lifted every groundfloor floorboard, we are still digging out subfloor mud, taking away rotten wood, and carrying out remedial work (airbricks, lowering outside ground level).

Be prepared for what you might find, and make sure you have the budget for a wrst - case scenario!