BEE Consulting, LLC

Rainscreen Technology

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Condo rot can be avoided by incorporating Rainscreen technology.

Condo Rot

Condo Rot Causes and Other Myths
Condo Rot Q & A


Recently up and down the pacific Northwest there has grown an increasing awareness that things are not as they should be with town-homes, condominiums and apartment buildings, even those which are only two or three years old. The City of Seattle has even struck a Moisture Intrusion committee to try and get a sense of why so many buildings are leaking and rotting and what can be done about it.

Many new buildings are being constructed incorporating an air cavity between the cladding and the main wall assembly so that any moisture which gets past the cladding can easily drain out or dry. This type of construction is known as Rainscreen, and is becoming increasingly popular since it has a very low failure rate and can be used with virtually any type of exterior finish.

So a solution is available for new construction but what about the thousands of units built to date that are not fitted with this system? And more to the point, how bad is the problem and how did we get to the stage where we are having to strip perfectly good looking buildings which are only two or three years old.

While there have always been problems with leaks into buildings until recently it was mostly thought of as a roofing or maintenance issue or connected to the use of EIFS (insulation coated with a cementitious layer) and stucco. With the increasing tempo of buildings being examined for mould, rot and structural stability it is becoming widely recognized that significant damage is now occurring which is unrelated to the type of cladding being employed. There is great debate as to the root causes of this.

What does appear clear is that the length of time that it now takes for significant failure to occur is down to two or three years rather than decades and that the accelerated failures seem to date from the 1980's and later. The common factors seem to be that from the mid 80's there was greater attention paid to reducing air movement through the building exterior, thus preventing the rapid drying out of occasional water leaks. In addition, the materials used for the exterior sheathing and cladding have become increasingly impermeable and more unlikely to dry out when wet. The result is that whereas twenty years ago a leak might take two or three days to dry out, now it takes weeks, which is long enough for rot to become established.

It is also now clear that it does not take a lot of water to create these disastrous situations where the entire exterior structure needs to be replaced. It simply takes a small amount of water over a long time.

So in order to clear up these urban myths about why Condo Rot is with us here goes with exploding a few of them:

Condo-Rot Causes and Other Myths

Condo Rot


The problems occur even when everything is done according to code and current Best Practices. Bear in mind that the same tradesmen work on the new Rainscreen buildings and these have very few problems. It could be heightened awareness but my own experience suggests otherwise.

EIFS and Stucco

When applied using a cavity or Rainscreen system EIFS works fine as does every other type of cladding that I can think of.

Vinyl Siding

Vinyl siding is thought to be immune to problems because it is perceived as being "open" in construction. It's not true and some the worst buildings I have examined have used vinyl siding.

California type design

Condo Rot

There is no question that a lack of substantial overhanging eaves contributes to water ingress problems, but taking the extreme case, there are practical difficulties in providing a sufficient width of eave for a 5 storey building to make a difference. Again, plain ,very exposed buildings work fine when fitted with Rainscreens.

Providing buildings with Rainscreen cladding systems is expensive and calls for specialized labor:

Depending on the type of cladding used we have found that the additional cost rarely exceeds 10% over the standard forms of construction. As for application, since the materials used are the same as normal construction there is only a small learning curve until the principles are absorbed. On a practical note almost all of the dozens of buildings we have constructed or rebuilt involved guiding the trades through the process. Mind you, my hair is now coming out in clumps!

My building is new and looks great so it should not have problems

It's heartbreaking sometimes to prove that how a building looks has little bearing on how much rot etc. is hidden behind the exterior skin . I have lost count of the number of great looking buildings under 5 years old that people were shocked with the extent of the damage after the siding was stripped off.

Condo Rot Q & A

Can't you tell by looking at it if it's O.K.?

Condo Rot

The short answer is no. Sometimes I have a pretty good idea about the building in general but specific locations can be deceptive. The only real way is to take extensive moisture content readings of the sheathing behind the siding then follow up with actually opening up some areas to confirm the readings. For example material might be completely rotted out, yet be dry to the meter.

What if my building only has a few small problems?

Generally this only occurs in older buildings and for those it makes sense to repair things a well as possible then put in place an enhanced monitoring system to chart the ongoing health of the building and carry out an aggressive maintenance program. Essentially the approach is to make the building last as long as possible for as little money as possible.

What if my building has extensive problems?

When one is faced with repairing over 15-20% of the exterior it is usually necessary to consider total replacement of the exterior building envelope. When extensive problems are found it is extremely difficult to tie in repairs without creating another potential leakage point and the strong potential for future rot. Again, many repairs that are made subsequently fail with worse results than before and in less time.

If my building is rebuilt will, it last longer than the last time?

Condo Rot

One of the really unfortunate aspects of the reconstruction business is that most of the time the buildings are repaired in a way that mirrors the original construction. I don't think that many tradesmen or contractors deliberately set out to create buildings that rot but there is still the perception that current building practices are sufficient to prevent those leaks which lead to rot and mould from occurring. The truth is that buildings which are rebuilt in a manner similar to their original will have the same problems no matter how much attention is paid to workmanship etc.

What type of construction would you recommend?

The only type of construction that we use for multi-family residential and commercial buildings is called Rainscreen. This method of construction supports the siding etc. on vertical battens to create a ½-3/4" cavity or air space. This cavity is open at the top and bottom of the wall and this allows it the drain any water which gets through the cladding as well as allowing any residual moisture to dry out quickly.

How much does it cost?

This is the part that scares everyone to death and often with good reason. The costs of a total strip off is usually in the $35-45 per square foot of exterior area. This includes everything including windows, decks etc. Many contractors charge much more than this using their "experience" as a rationale, but with good planning and contract management most jobs should come in around those numbers.

Because the cost is usually similar no matter what types of materials are used(within reason!), my approach has been to try to incorporate all those things that the owners would like to see or in some cases, see removed! It is usually possible to upgrade the windows to have better thermal control especially in the winter and summer or to change the exterior in subtle and not so subtle ways to reduce the maintenance requirements and improve the long term appearance of the building.

The objective is to provide long term gain in return for short term pain.

What are the problems which face owners if repairs are contemplated?

Condo Rot

The biggest single issues are money and trust.

Money becomes less of a problem if there is trust. The fact is that any repairs are expensive and usually cost more than anticipated because the extent of damage is usually greater than the owners emotionally anticipate. It is absolutely vital for transparency in all discussions about large scale repairs and it has been my experience that councils that are less than candid with their owners end up creating huge problems for themselves.

It is vital that everyone is allowed and encouraged to speak up about their wishes and fears. I have found it useful for a building reconstruction committee to be set up to get input from owners and help formulate a wish list of features which might be incorporated in the reconstruction. This committee must be given enough time to allow for all views to be expressed, although an effective leader should be present throughout that can help steer the process to a conclusion. If done well this process can generate great enthusiasm which helps get everyone through the few months of living behind green mesh!

Condo Rot

Is there life after Condo-Rot repairs?


BEE Consulting, LLC

170 W Dayton St., Suite 206
Edmonds, WA 98020
Phone: (425) 672-3900
Fax: (425) 712-8608

1638 NW Riverscape St.
Portland, OR 97209
Phone: (503) 222-1715
Fax: (425) 712-8608

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