Cot­tage foun­da­tion con­cerns pose dilemma

Winnipeg Free Press - Section G - - HOMES - ARI MARANTZ

QUES­TION: I was read­ing an ar­ti­cle about the proper foun­da­tion for Man­i­toba soil on the In­ter­net and was di­rected to your site through the ar­ti­cle. I have a small prop­erty in Mat­lock, close to Win­nipeg Beach. We have spent the last few years prep­ping the prop­erty to build a cot­tage. That in­cludes re­mov­ing trees, an old con­crete hold­ing tank, tree stumps and other un­wanted garbage.

We can­not seem to get a firm an­swer on what type of foun­da­tion to have. The cot­tage will be about 900 square feet. I have been told by the plan­ning depart­ment in Selkirk that a spread form foot­ing would do the trick. When I went back to ask more ques­tions, they said it might be a good idea to have the foun­da­tion piled. But when I talk to the lo­cals they say you don’t need piles, a lot of cot­tages are on con­crete foot­ings; just keep the tem­per­a­ture un­der the cot­tage above freez­ing in win­ter.

I just can­not seem to get a firm an­swer from any­body in the vil­lage. We are try­ing not to be over­sold and lean­ing to­wards a con­tin­u­ous spread form foot­ing.

What do you think? Any in­sight would be help­ful.

Thank you, Stephen. AN­SWER: You have posed an in­ter­est­ing ques­tion about a dilemma many peo­ple face when build­ing a sum­mer home or cot­tage. The typ­i­cal con­struc- tion meth­ods em­ployed with a deep foun­da­tion or crawlspace of a year­round home may not be nec­es­sary, depend­ing on your pro­posed us­age.

The an­swer to your ques­tion about the spe­cific type of foun­da­tion re­quired will de­pend on sev­eral fac­tors, mainly its in­tended use — whether you want to build this as a cot­tage for sum­mer use only or as a fully in­su­lated home us­able in the win­ter as well.

If you’re build­ing a sum­mer cot­tage, with min­i­mal heat­ing sys­tems and plans to drain wa­ter lines be­fore the win­ter, you may wish to build the cot­tage with an open area un­der the floor to al­low easy ac­cess to plumb­ing drains, pumps and wa­ter sup­ply pipes. Also, hav­ing the floor joists raised off the ground by a me­tre or so, with min­i­mal ob­struc­tions, will al­low the soil un­der the cot­tage to quickly dry af­ter heavy rains or the spring melt. In that type of sit­u­a­tion, a sim­ple con­crete spread foot­ing sup­port­ing treated-wood posts be­low the main beams of the floor may be ad­e­quate.

If you want a mainly sum­mer dwelling, but with the ca­pa­bil­i­ties of year­round heat­ing and use, you will have to go one step fur­ther. The foot­ing on grade may still work, but you will have to build a fully in­su­lated skirt­ing or knee-wall around the perime­ter of the cot­tage be­tween the foot­ing and the un­der­side of the floor joists. This is nec­es­sary to in­stall heaters un­der this area to pre­vent freez­ing of plumb­ing pipes in the win­ter.

In that type of sce­nario, you should also in­stall a com­plete poly­eth­yl­ene vapour bar­rier over the dirt floor of the crawlspace to pre­vent mois­ture in­tru­sion through the soil into the crawl space and house. As well, in­stal­la­tion of sum­mer vents or screens will be needed on all sides of the skirt­ing to dry out mois­ture ac­cu­mu­lated in the crawlspace over the heat­ing sea­son. These can be re­mov­able or cov­ered with rigid foam in­su­la­tion for the heat­ing sea­son to main­tain heat for the crawl space in the win­ter months.

While both of the above con­struc­tion meth­ods will rely only on a con­crete foot­ing, es­sen­tially built on grade, they may still be sub­ject to sea­sonal move­ment due to un­sta­ble soil or frost heav­ing. I agree that main­tain­ing a heated crawlspace may help min­i­mize move­ment of the foot­ing, but it’s not a guar­an­tee that move­ment will not oc­cur. Heav­ing due to frost, or dra­matic mois­ture changes in the soil be­low the foot­ing, is still quite likely. Depend­ing on the lo­ca­tion of your pro­posed sum­mer home and the soil con­di­tions, this may range from mi­nor move­ment to ma­jor set­tle­ment, caus­ing cracks in the foot­ing and jam­ming doors in the build­ing.

From ex­pe­ri­ence with my own sum­mer home, in a sim­i­lar area near your pro­posed cot­tage, the foot­ing method is quite re­li­able if in­stalled prop­erly. While we have ex­pe­ri­enced mi­nor set­tle­ment with our own place, since I poured the re­in­forced foot­ing and com­pleted the cot­tage about 15 years ago it has not been se­vere enough to even re­quire trim­ming doors. The only re­me­di­a­tion needed was shim­ming of the knee-walls sup­port­ing the ex­te­rior walls above the foot­ing.

Our fully in­su­lated crawlspace has only been heated for a cou­ple of win­ters af­ter ini­tial con­struc­tion, which seemed to make lit­tle dif­fer­ence to the over­all move­ment. What seems to be a big­ger fac­tor is the amount of snow and rain, which can af­fect ex­pan­sion or con­trac­tion of the soil in and around the crawlspace.

Some of the mixed mes­sages you are get­ting from the lo­cal plan­ning depart­ment stems from de­bates that have gone on in var­i­ous ar­eas for many years. While many homes and cot­tages have been suc­cess­fully built on foot­ings, whether sup­port­ing a deep foun- da­tion or built on grade, move­ment is al­ways a pos­si­bil­ity. Be­cause we have vary­ing de­grees of ex­pan­sive clay soil for sup­port of the foot­ings, move­ment may vary from slight to ex­treme.

Drilling deep holes in this soil and pour­ing re­in­forced con­crete piers, com­monly called piles, for sup­port of the build­ing is al­ways a su­pe­rior sys­tem. The depth of the piers will en­sure that frost heav­ing should be elim­i­nated and sink­ing is un­likely, un­less very poor soil con­di­tions ex­ist. For this rea­son, homes or cot­tages sup­ported over top of this type of foun­da­tion are more sta­ble.

As with many con­struc­tion projects, the cost of build­ing and af­ford­abil­ity is al­ways a fac­tor. While in­stal­la­tion of a sim­ple con­crete spread foot­ing may be all that is re­quired for a rea­son­ably sta­ble foun­da­tion, it will never be as re­li­able as deep con­crete piers.

The build­ing of­fi­cials that have ju­ris­dic­tion in your area will only re­quire that con­struc­tion meets the ap­pli­ca­ble build­ing codes, but keep in mind that those are min­i­mum stan­dards and not best prac­tices. It’s al­ways a good idea to go the ex­tra step and in­stall the bet­ter sys­tem, but you will have to de­cide whether the peace of mind as­so­ci­ated with con­crete piers is within your bud­get.

When it comes to foun­da­tions, for homes or cot­tages, noth­ing can beat piles.

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