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Restoration & Refurbishment

Damp in wooden floor - Ventilation problem.

Anonymous user 28/02/2024 - 3.54 PM

Our house has a suspended wooden floor in the lounge at the front, but many years ago the rooms at the back of the house were filled in with solid floors, and as far as I can tell there is no ventilation at the rear of the lounge. There are three air bricks across the front of the room, but nothing else. A few years ago we had the drive replaced with block paving and they (inadvertently I guess) blocked the air bricks with sand. Up to that point I suspect the ventilation under there was just about good enough that it wasn't causing a problem, but we now have a floor with high moisture, and a lot of evidence of fresh woodworm. I've unblocked all the air bricks a couple of months ago but the moisture content isn't going down at all and I'm at a loss as to what to do next. I don't want to just replace the floor and risk the same thing happening again. Short of removing it and filling it all in with solid floor, what options do we have?

Are you a tradesperson and able to answer this question?

4 Answers

Anonymous user

Hi there if they have raised your drive to high you may be getting damp from outside.. minimum distance between your drive and your dpc (damp proof course) should be 150mm or 2 bricks. Your dpc is at the same level as the bottom off your front door. Hope this helps
Answered17 November 2020
4

C N CONSTRUCTION

Rating: 5 out of 5
Abergavenny
Try a dehumidifier in room for a couple of weeks c if it will draw moisture out
Answered17 November 2020
1

G C Regan

Rating: 4.9 out of 5
Grays
Nothing wrong with the previous answer, but also when the solid floor was laid at the rear a minimum of 3 X 100mm Soil pipes should of been laid from rear of front room to the air bricks in the rear wall (flow through of air), So your choice is to dig up Three channels in rear room and lay soil pipe for ventilation or have solid floor in front. Also under wooden floor make sure you have a minimum gap from bottom of joists to the ground of 100mm. also to the front where the moisture is and lack of ventilation could lead to a build up of rador gasses which can lead to serious health issues
Answered23 November 2020
0

Anonymous user

Ventilation in floors, especially suspended timber floors is very important so as not to facilitate the build up of moisture within the floor structure. This moisture build up can cause deterioration not only the timber joists but also any coverings placed over the joists. Ventilation in suspended timber floors can be achieved by installing vents below the joist level in opposite walls of the building and if possible on all sides of the building These vents must be enclosed to prevent air getting into the cavity of block wall construction. These vents will facilitate cross flow ventilation below the joists. Often these vents can be blocked, restricting the amount of ventilation being achieved. They can be blocked in a number of ways including, higher ground level outside, vegetation growing, footpaths and also builder’s rubbish/rubble left under the joists. Another common way these vents can be blocked is by an extension with a solid floor being built onto a property without providing proper access to the original vents. The recommended minimum area of ventilation required for under a suspended timber floor is 1500mm2 for every metre of perimeter of the structure. Cross flow ventilation was traditionally achieved by placing sleeper walls at intervals throughout the sub-floor. The sleeper walls would be honeycombed in nature to facilitate airflow. A damp proof course (dpc) was placed on top of this wall and then the wallplate and joists were positioned on this to reduce the chance of rising damp at this point. In older buildings it is important to check to see if there is adequate ventilation as this could be an indication that the floor members either have deteriorated or are deteriorating. Some signs of inadequate ventilation would include cupping of flooring/floorboards, doming of floors, general decay, odour and mould. Cupping occurs when the undersides of the floorboards absorb moisture and it will swell causing a concave effect to appear on the top of the floorboards. Doming occurs when there is excessive moisture present in the floorboards that have been left no room for expansion and they lift in a continuous curve. When the moisture dries in periods of prolonged dry weather the floorboards will normally return to normal. To sum up floor ventilation is very important not only for the integrity and strength of a building but also for the health of its occupants. If any of the defects noted above are observed in your property then especially the lack of vents in outside walls (of timber floors) then there may be inadequate ventilation and remedial measures may have to be taken.
Answered3 December 2020
0