Trained Eye

 
 
 

Piles vs Floating Sunroom

Question:

Hi.

 Thank you for your weekly informative column. We read it faithfully every Sunday.

 We are planning on adding a sunroom to our forty-three year old bungalow.  The question is, how do we decide which type of sunroom is suitable for us. We have one sales rep telling us that the "flotation" sunroom is the way to go because of the shifting ground and the Winnipeg "gumbo", however, another telling us that piles is the only way to go.

 The "flotation" sunroom sounds very appealing as our house has shifted in the past year and we now have hairline cracks in the ceilings of our living room and a couple of our bedrooms.  The sales rep told us a story of a competitor who uses piles and the sunroom literally tore off of the house from shifting. 

We would certainly appreciate your opinion on this. We want to make a decision within the next few weeks so we may start building the sunroom this coming fall.

Thank you.

Answer:

I don’t know if my reply to your question will be in time for your decision, but I hope it helps somewhat. This is an excellent inquiry and one that may get differing views from everyone you approach.

Because of our expansive clay soils in Manitoba, settling, shifting and heaving of various types of foundations is an unfortunate reality. This may or may not occur to a large extent in your new sunroom addition, but that is only half the problem. The real issue is the ongoing movement in the original home and foundation and how that will affect the new structure.

There are two general methods for dealing with the movement issue, which you have outlined. The first is to install the sunroom with an adjustable support structure that can be lifted or lowered at will, corresponding to the movement in the home and addition. This may be done using ground augers, often referred to as “Groundhogs”, or with a combination of footings and adjustable teleposts. Both of these methods will allow relatively easy adjustments as long as access under the structure is possible. The beauty of this system is that the sunroom addition structure can be adjusted to accommodate not only movement in the soil below, but also movement in the original home that it is attached to.

The other method you mention is the installation of piles for the structure to rest upon. The “piles” you refer to are typically poured, reinforced concrete piers of varying depths, depending on loads. These are normally installed by drilling several deep holes in the soil, between 6 and 12 inches in diameter, and filling them with concrete and reinforcing steel re-bar. The theory behind these poured-in-place concrete columns is that the bottoms extend well below the frost line and eliminate typical settlement and frost heaving, common to shallow foundations. If installed correctly, they will certainly be the most stable type of support structure for the new sunroom addition. Unfortunately, that may also be their biggest drawback.

The older home that you live in is probably built on a raised concrete foundation, sitting on a concrete footing, 5 to 6 feet deep in the ground. This style of foundation may be subject to seasonal settlement, depending on soil moisture and temperatures fluctuations. While most of this settlement should have occurred in the first 10 to 15 years after construction, some may still be ongoing. The problem with this movement is that it may be at a different rate and direction to that of the new addition. Or alternatively, if the new sunroom is extremely solid, due to the pile foundation, it may not move at all while the house continues to settle. If either of these scenarios occurs, the sunroom could easily pull away from the home, as one salesperson has described.

There are numerous additions built in southern Manitoba where this very problem has been ongoing, often for many years. The possible ramifications are cracking in the floor, exterior siding or at the junction of the roof of the addition and the home. Any of these issues could allow water and pest intrusion into the sunroom or main house. In that case, the results could be very serious, requiring regular major repairs. For this reason, an adjustable style of foundation is probably the better solution than piles.

Whatever your decision, make sure you ask for several things from the contractor or company building the sunroom addition. First, ensure that they are applying for all the applicable building permits to ensure proper scrutiny of the addition plans and regular inspections by the municipality Building Officials. Secondly, find out about any warranties on the roof structure, windows and other components of the sunroom. Finally, ask how long the company has been in business and how many of these additions they have built. A reputable company should be able to provide you with references from satisfied customers and possibly even an installed one that you can look at in a customer’s home. Like any renovation, obtain at least 3 quotations and ensure the different companies are comparing apples to apples and taking everything into consideration.

 

Contact

trainedeye@iname.com

204-291-5358

P.O. Box 69021
#110-2025 Corydon Ave
Winnipeg, MB
R3P 2G9