This delightful house, approximately two hundred years old, was probably coping perfectly well with its environment. Then, approximately thirty years ago, someone decided to intall a new floor.  They did everything as they should do, probably even put a damp proofing membrane beneath the new screed; they certainly installed an asphalt coating over it.

Result, all the moisture in the old floor that had been happliy evaporating, and then disappearing into the wild blue yonder, now had nowhere to go. Except that is for into the base of the walls, where it rose steadily upwards.

To counteract this, an injection dpc was attempted - in 600mm thick, rubble-filled walls.  They may as well have lit Joss sticks to tempt the damp away.  The current condition of the walls is displayed in the photo below.

Now, as it isn't going to be possible to resurrect the original flagged floor, it will be necessary to apply cavity membranes to the base of all of the internal walls.  Not my idea of how old houses should be treated, but it's better than trying to live with permanently damp walls. Moral, dont mix modern practices with old properties - they don't usually work.

Just as a matter of interest, this house had been locked up over the summer and it seems to have been a meeting point for the local fly population.  They must have been having some sort of party on the window cills, and this is what happens to them when they've had a little too much to drink!

A strong stomach was required to inspect the window reveals

Client(s)                                  

Property                                   Derbyshire 

Instructions                             

To inspect the property and provide an opinion on any areas of dampness and/or timber rot/infestation. In addition to the main building, an inspection was also made of a detached garage and a detached outbuilding. In the main, these latter inspections were carried out in order to suggest suitable renovation methods.                                               

Background                            

 The clients are purchasing the property and require the above information as part of that process.

Disclosures                             

I am not aware of any affiliation, financial or otherwise, with the client or the property.                                        

Limitations                              

Nil

Restrictions                             

The survey was non-invasive.

Date of Survey                         

October 2008

Weather                                   

Dry, sunny.                                                 

Viewing Orientation

Unless otherwise stated, all observations are made as if looking towards the house from the front.

Type of Property

Detached cottage c1810 and having accommodation over two floors, including a rear projection.                                        

The main property is further extended at the rear and there is also a conservatory and timber-clad garden room.  The rear extension, which was built within the last twenty years, was not accessible.

External Observations

The house is orientated such that its front elevation faces in a southerly direction, and it has solid, stone walls beneath a blue slate roof.

Given the property’s age, there will not have been a damp proofing course (dpc) included at the time of its construction, although there are clear indications of a retrofit, injection dpc in all of the 600mm thick (nominal) external walls.  The walls themselves have been pointed with a sand and cement mortar, which is an unfortunate material to have used in this instance, lime mortar would have been more appropriate.

External ground levels are at, or just below, internal floor levels.

I did not detect any signs of leaks from any of the guttering, although this should be checked again during a period of heavy rainfall.                                              

The blue-slate roof appears to be in good condition and later observations, made from inside the loft spaces, indicate that the right-hand section of the main house has been re-slated within the last forty or fifty years.                                              

There are three brick, chimneystacks associated with the house and all have open pots atop.  The one to the front, left-hand side, and also that at the rear may also house capped flues.

Attached to the right-hand gable wall of the main house is a metal framed and clad garage.                                               

The detached garage is situated approximately twenty metres to the south of the main house and it has solid, stone walls with an approximate thickness of 400mm; this building also has a blue-slate roof.                                               

I understand this garage was constructed during the 1960’s or 70’s, and although it has solid walls, there is also an integral dpc; there are no high ground levels that would compromise this.                                               

The rear outbuilding is much smaller in stature and seems to have been built at the same time as the house.  It too has solid walls, but there is neither an integral nor retrofit dpc in these.

Internal Observations

Loft Spaces                             

There are three distinct loft areas: two above the front section of the house and a further one in the rear projection. All of them were entered and inspected as far as possible.                                               

The loft over the right-hand section of the house has sarking felt beneath the slates, which indicates it has been re-slated within the relatively recent past.  The majority of the roofing spars in this section were visible and there were no indications of rot or active insect infestation.  Moisture content of the timbers was <14%, and at this level, rot will not commence or flourish.                                               

The other two lofts do not have sarking felt beneath the slates although I think they too may have been re-slated as the external appearance of the slates indicates the entire roof was renovated at the same time.                                              

In addition, these latter lofts are underdrawn with reed and lime-plaster, and most of the timbers were thus not accessible.  However, where I could see them, these timbers were also in good condition, i.e. without rot or insect activity. They also had moisture content well below the level at which rot could occur.                                               

Loft insulation is below current standards in all of these lofts.                                               

There were no indications of any leaks in the roof covering.

First Floor                                

With the exception of the first floor bathroom, there were no indications of any problems in any of the rooms on this floor.                                               

The bathroom appears to have had a leak in the vicinity of the w.c., although this has now been attended to and the timber in the immediate area is almost as dry as that surrounding it. Moisture content of the affected flooring timbers is currently <17%, and as rot cannot survive in timber with a moisture content below 20%, these timbers are no longer in danger.  However, should this leak reoccur, this situation might change.                                              

Also in the immediate area of the lavatory pan were desiccated remains of a fungus of the Peziza spp. but these were obviously extinct.  Peziza does not attack timber, although its presence indicates the substrate it was growing on must have been extremely wet at one time. 

Ground Floor                           

The ground floor is of solid construction throughout, and I understand this was re-laid at a higher level than the original one.  I am not exactly clear when this happened but it was within the recent past, perhaps during the 1960’s.                                              

I also understand that a membrane may have been incorporated in this floor but I am not sure of this. In any case, it has been sealed with a top layer of mastic asphalt, at least in the front, right-hand and rear reception rooms.  The left-hand rooms have either vinyl tiles or quarry tiles on top of them, although I expect these areas also have a mastic layer beneath those coverings.                                               

The majority of the walls are severely distressed at their lower levels.  The plaster has blown off and some of the skirting boards are beginning to rot, particularly in the front, right-hand living room.  In the rear reception room the plaster has actually been removed from the walls to a height of approximately 400mm, and this too must have been because of similar distress. 

The base coat plaster, beneath the surface skim on all of the walls, appears to be a very weak mix of sand and cement, and it will probably have been applied during the retrofit dpc exercise; a mix as weak as this will have been virtually useless at fulfilling its design functions.  To achieve this requirement it would have needed to be a strong 3:1 mix of well-graded sand and cement.

Moisture meter profiling of the masonry, and moisture content readings taken from the skirting boards gave clear indications of rising dampness.                                               

There were no indications of problems in the timber, garden room and other than for the above, no other faults were noted in the downstairs rooms.

Discussion/Conclusions

The only significant problems in the main section of the property relate to the poor condition of the ground floor walls, which are suffering from rising dampness; this condition applies to all of the internal walls.

Although it has been ‘treated’ in the past, by the installation of an injection dpc, the procedure used will have been ineffective; and given the thickness and construction of the walls, any similar treatment will produce equally poor results.                                               

This condition (rising dampness) exists because of changes made to the property since it was first built, and in particular the raising, and subsequent asphalting, of the floors.

There will also be other factors to consider, such as condensation etc, but in the main the significant alterations to the floors bear most responsibility for the current distress.

When the property was first built, its floors would probably have been overlaid with flagstones, or even left as bare earth, and would have been naturally permeable; thus they would have allowed any moisture in the ground to evaporate easily. 

The moisture so released into the property’s internal atmosphere would then have exited the house via the naturally ‘leaky’ sash windows, doors, and open fireplaces etc.                                               

The alterations to the floors, and in particular the inclusion of the impermeable layer of asphalt applied to them, have denied the property this evaporation path, and the moisture in the ground beneath is now being forced to evaporate via the lower reaches of the walls. This continual and long-standing condition has overwhelmed the rather ineffectual, retrofit dpc, and the results are now plainly visible in the lower reaches of the walls.

As it would be impractical to return the floors to their original condition, and a further injection dpc would be as ineffective as the present one, it will now be necessary to manage this moisture; ‘curing’ it, in the sense of stopping it rising into the base of the walls, is no longer an option.

To this end I shall be recommending that you install a cavity membrane system on all internal walls, to a height of 1500mm.  This can then be plastered with a gypsum plaster. As mentioned above, this will not cure the damp per se; but it will prevent it from affecting the internal environment of the property.

A general increase in ventilation, perhaps by re-installing open fires and adding extractor fans in moisture producing areas would also be beneficial.

Regarding the detached garage.  I understand that it is the intention to install a block and beam floor. If you feel you have sufficient space, I would also clad the walls with aerated concrete blocks, leaving a small, finger cavity.  Not only should this provide you with sufficient ‘U’ values to satisfy current building regulations, it would also circumvent the potential for penetrating moisture on the exposed elevations.  Naturally, cavity drainage in the form of weep vents will be required but your builder should be familiar with these devices.

I did not see any indication of rot or current insect activity to any of the roofing timbers in this structure and their moisture content was below the level at which rot could occur.                                               

 The above suggestion, of building aerated concrete block walls, is probably inappropriate for the smaller outhouse, as this may reduce available floor space to an unacceptable degree.  However, improved insulation would be very desirable, and so that you can achieve this it would be wise to clad the walls with an insulated, dry-lining system. This will also help to combat condensation, and I shall enclose a sketch with this report showing how you may construct such walls.

However, you should note, if Building Regulations are required for the conversion of this building, 25mm Kingspan, as shown on the drawing, may not satisfy their requirements, and the insulation may have to be increased to 50, or even 75mm.  You will need to clarify this with your architect or designer.

If this is indeed the case, the cross-section of the timber members will also need to be increased, and this too will reduce floor space. I’m afraid it’s a difficult situation whichever way you look at it, and the gain from using timber, as opposed to block walls, may only amount to 25mm or so.

There are clear signs of insect infestation (woodworm) in a minority of the timbers in this building, but as far as I can tell, this is historic.  Certainly, at the present time, there is insufficient evidence of activity to recommend the use of insecticides.  However, as discussed on site, you should monitor the situation and look for symptoms in the late spring and summer months of 2009, i.e. frass trails appearing on vertical surfaces of the timbers.  If these do appear, please contact me again for further advice.

Conclusions                            

The installation of the solid floor has resulted in rising dampness in all of the ground floor walls.

In order to manage this problem effectively, you should hack off the plaster on all ground floor walls to a height of 1500mm, so that the masonry beneath is exposed.  This includes the day room to the left of the building where presently there is a timber wainscot and dado rail.  However, the downstairs shower room is in an acceptable condition and treatment need not be extended to here.

You should then apply a cavity membrane system such as the Newtonlath 2000, which can be re-plastered in line with the manufacturer’s instructions. You may research this product at their website, which can be found at: www.newton-membranes.co.uk/newlath.htm. There are other, similar systems on the market should you so wish.                                               

You should also consider the installation of good quality extractor fans in all of the moisture-producing areas, particularly bathrooms and kitchens.  The presence of these devices will help to reduce the effects of condensation.                                               

I would expect the cost of the above works to be in the region of six to seven thousand pounds, and you may wish to bear this in mind during any negotiations. 

I trust the above is satisfactory for your purposes but if you require further clarification please do not hesitate to contact me.

Signed                                                                         Surveyor

The above findings are based partly on the interpretation of results from a standard non-destructive inspection; this, by necessity, has limitations. If you require confirmatory/definitive diagnosis of my findings then this can be undertaken by the use of destructive methods of investigation: these will involve some damage and costs.