Dry Rot (Serpula lacrymans) was discovered below a suspended timber floor inside a property in Sheffield when the owner of the property had workmen in to lay a new oak flooring. As the furniture was move out of the room it became apparent that there was a problem with the timbers being a dark brown colour and having large cuboidal cracking occurring. All Dry Damp Proofing Ltd from Barnsley near Sheffield were contacted to survey and quote for remedial works needed before a new Oak flooring was laid.
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We visited the site and spoke with the owner who told us it was a dry rot problem ( We then had to confirm this). We were shown a few pieces of decayed timber but the bulk of the floor had been removed leaving us with a bit of a problem. We could not see where the outbreak had been and therefore had to rely on the descriptions of the customer who was not present when the floor was removed. The flooring contractors were not present either. Suffice to say a picture was built up and we could confirm that we were dealing with a case of dry rot from the evidence present.
No 1 Locate The Source of Moisture
After identifying the type of rot the next job was to find where the source of moisture was coming from and after surveying the property internally and externally it became clear to us where the main problem was.
Rain water was running into the channel at the side of the house off the wall and drive. the ground level outside is around 50mm higher than the internal floor level and the air bricks were Positioned down in holes so they were level with the internal floor slab, this allowed water to run into the property each time there was heavy rain.
The property used to be an old out building to a larger property opposite and this had over time been converted into a habitable dwelling. We found this out from speaking with the owner. This may account for the drain hole that was in the middle of the bedroom floor. the out building may have been used for slaughtering animals or washing them down. The concrete floor also had a fall (gradient) and channels in the concrete from the walls with the air bricks down to the main drain hole.
This also lead us to suspect the room had had problems with water coming in for a while before the current owner took charge of the property. the far wall with the air vents is a solid wall and is very exposed to the elements being at the top of a hill. On the inside polystyrene lining paper was below the main wall paper and there was evidence of black spot mould on the wall.
So we found the source of moisture and what also added to the ideal conditions needed for dry rot to thrive ? High humidity, this was created by the radiator pipes that ran below the suspended timber floor along the wall where the vents were placed and over to the bay window. these were sat on the slab and any water coming in when the heating was on would have been warmed up as it passed, yes it was subtropical down there and in total darkness for proper cultivation conditions for the fungi.
No 2 Find The Extent of The Problem
After the initial survey and confirmation of the problem and causes we had to find the extent of the Dry Rot and how far it had spread. this was after consultation with the customer and this was a paid survey. It is possible for Dry Rot to grow through masonry destabilizing the structure. So test holes were cut into the plaster at predetermined intervals around the location of the outbreak looking for any further evidence by way of strands, Mycelium or spores, we are also looking for high moisture levels in any timbers and masonry. This investigation forms the basis of the quote as it dictates how big the area is to treat, what systems are to be used and to what extent they will be applied.
We decided to dig out the old air vents and put in new air bricks using a telescopic vent that would be higher than ground level on the outside so rainwater would not run into the property via this opening. We then decided to run a storm drain along the property and out to the rear garden to a soakaway. This would keep surface water away from the wall floor junction. As the stone wall was of a solid construction it was decided to apply StormDry Masonry Protection Cream to the surface, this would stop cold bridging of this area which is very exposed to the elements. when the stone becomes wet when it rains the wind on the wet masonry will make the surface temperature drop on the outside, the cold temperature will transfer through the wall to the inside and this can cause problems with condensation and black spot mould forming when the humidity is high. StormDry Masonry Protection Cream stops rainwater penetration and rather than soak in the rain will bead up and run off. With it being a pore liner not a pore blocker it still allows water vapour to pass through the structures fabric making this an ideal remedial work product.
So The first job was to clear everything out of the room and take off the radiator. We decided to take the plaster off up to 600mm from the floor as we did not see the original outbreaks. The flooring contractors took most of the suspended timber floors away so it was the customer who had to explain where the outbreaks were found and in this instance there were two either side of the room.
Once the plaster was off and cleared away the joints of the stone and brick work were ground out to a depth of around 15mm, the masonry was then treated with a biocide as the last job of the day. the biocide had a 1 hour re entry and all care was taken in conjunction with health and safety procedures.
To reinstate the plaster we chose a sand and cement render containing an additive with zinc oxychloride this was applied to the walls in two applications. The kicker membrane at the base of the wall was incorporated into the design because a membrane is to be fitted on the concrete slab. We had very little information about the drain and its history that was in the middle of the room so rather than block it up we decided to add a sealed membrane over the floor. This way any moisture or water from the drain will stay below the membrane and if there is any ingress this can be evaporated over time or run towards the drain via the historic channels.
All Treatments are now finished
The room is now ready for the new suspended timber oak floor and decoration. We recommended that any paints used must contain zinc oxychloride and be water based to allow continued drying of the structure until it reaches equilibrium with the rest of the walls.